user 84948

I just bought my first Honda...a 2001 Honda Civic. When I purchased I knew the AC didn't work. Well now that I own it, time to see what is wrong.

So far the things I checked:
1. Ran and purchased a set of gauges and got the following readings both when the engine was off and when turned on and the AC was selected to "ON": Low Pressure port: 82 PSI; High Pressure port: 78 PSI.
2. I got a wrench and was able to manually spin the AC compressor clutch freely with little effort.
3. I swapped the relays for the AC compressor and the condenser fan with the same result.

The compressor just does nothing with the turn the AC on. What are my next steps in troubleshooting? How can I ensure the switch to turn on the AC is actually sending the signal (besides just seeing the green light come on)? How do I know that power is getting to the relay?

Thanks in advance to all of you!

ezone

Observe:
Do the radiator fans come on when you try to run the AC?

user 84948

No they do not.

ezone

2001....
Interior fan DOES run, yes?


Ok try a HVAC self test, see if its control unit has any codes. This was posted under 2002, I assume it's the same

Self test:

Begin with the key OFF.

Turn the fan **** to OFF
Hold down the RECIRC and rear window defogger buttons
Turn the ignition switch to ON (do not start the engine)
Let go of the 2 buttons

Recirc and rear defog buttons light up,
recirc goes out in like 2 seconds then AC light comes on...
then shortly (maybe 10 seconds) the self test finishes and AC light goes out.

If there are codes the recirc light will now blink a code number.
If no codes the recirc light stays off.


If you get any codes, report back
---------------------------------------------

If no joy......

Got a volt-ohm meter? Know how to use it?
Go to the AC system pressure switch and unplug it.

Start the engine and turn the AC system on.

Test the blue wire, it should test as grounded.

If it is not grounded, take a jumper wire and connect the other wire (blu/white) to ground and see if the AC system kicks on, just to verify it can run when the PCM commands it.

user 84948

No trouble codes came from the HVAC self-test. I am fairly new to electronics. I started reading up on it last night. I do have a multimeter though which I used to ensure all fuses in both panel boxes were good (continuity).

Two questions for this next test:
1. I don't have a wiring diagram for system yet (trying to find one for this model year), so is the AC system pressure switch the main or only electrical connector on the compressor?
2. How would I test the blue wire with a multimeter? Which setting should it be on and where should I place the red and black leads?

Thanks for your patience as I learn my way through this.

ezone

The pressure switch is not on the compressor. It's mounted in the top of the receiver-drier, #5 in this pic:


Or #15 in this parts diagram


Google images are not cooperating today.
Continuity test

Black (neg) lead on battery negative post, (battery and chassis ground)

red lead to the blue wire (use alligator clip on the lead, holding a paper clip with one leg bent straight as your probe)


=====

I'll assume at this point you find it is not grounding, so use a wire to supply battery ground to the other terminal in the connector (blue/white wire?) and see if the system kicks on.

I am NOT a good teacher LOL. I have a hard time starting at square one when I'm thinking waaay far ahead.

user 84948

Thanks for all that information. I just found the 2001 Honda Civic Service Manual thanks to this site. 2,900 pages!!! awesome stuff inside including the diagrams I was needing. I will give what you suggest a try and report back.

user 84948

So, I stuck a paperclip in the blue wire connection and touched the paperclip to the red lead and the black lead went on the negative battery post. I have continuity (when engine running and just in "ON" position), however I have no voltage readings when touching the same connections with the engine running and AC selected on.

I then bent the paperclip and stuck one end in each of the two terminals on the electrical connector, but nothing happened when starting the car and turning on the AC.

Trying to also follow the service manuals troubleshooting steps, it asked me to "Measure the voltage between the No. 9 terminal of
under-dash fuse/relay box connector F (12P) and body ground with the under-dash fuse/relay box connectors connected." I inserted the paperclip on the wire-side of the No. 9 terminal, but I don't know where to find the body ground in or near the fusebox.


****EDIT: Upon looking at the wiring diagram, it seems I made a mistake in my readings. When I tried to get my voltage readings off the the pressure switch connector, I had the paperclip in the blue wire terminal (so I was trying to get readings from two ground points). I switch the paperclip to the blue/white terminal and with the car in the "ON" position I got ~12V. I then stuck a paperclip in each terminal and checked for continuity between the two terminals.....nothing. Would this point to the AC pressure switch electrical connector as being the point of failure?

ezone

So the blue wire is grounded?

Right, ground plus ground =0v.

K, that shouldn't do anything as the pressure switch should have had continuity already and the system was not working.
Next:
F#9 should test as a ground after you reconnect the pressure switch, it is the same blue/white wire that you just checked at the pressure switch.

You found 12v on the blue/white wire in the pressure switch connector (disconnected from the switch), so I think that tells me it's connected to something on the other end (at the fusebox)


Next would be checking the yellow wire at fuse box connector E #10 OR checking E #24 at the PCM.
It should be grounded under the same conditions the previous wires are grounded (engine running, AC turned on).
If you manually supply ground to the yellow wire, the PCM should command the AC compressor and fans to run (if the PCM can do its job).


Question:
Does the car exhibit any other odd electrical issues??? Like dome lights not working right, warning beeper not working, washers or intermittent wipers screwy, or power locks not perfect?
If so, try doing self tests (mode 1 and mode 2) for the multiplex control unit

You could have connected to just about any bare steel under the dash for a ground, just double check and verify it actually IS a ground before you continue testing....Wrong readings because of a bad tester hookup can make you pull your hair out.

The battery neg cable goes directly to the steel body (chassis), so the entire body, frame, sheetmetal, engine and trans are all grounded: "chassis ground", "body ground", or "common ground"..
No.
You tested and found the blue wire to be grounded, and you jumped ground to the blue/white wire and the AC system did not operate, so the problem is "further up the ladder". This is (probably) where the trouble guide leads you to the test at the fuse box.


I was doing about the same thing, just using a point in the wiring that was much easier to reach. I'm getting old and fat, I don't want to be crawling under a dashboard unless I absolutely have to LOL
-----
When troubleshooting electrical stuff, I don't always go to a troubleshooting chart. I grab a wiring diagram and see what I can learn about how the system operates overall, then figure out how and what I can test on my own first.
-----
For the next steps-- checking the yellow wire-- I would probably flop the glovebox open and check it at the PCM connector E#24 just because I can sit in the doorway to do it instead of crawling to reach the fuse box..

user 84948

Correct the Blue wire is grounded.


Lets assume I jumped it wrong or didn't seat the clip properly. When I stuck a separate paperclip in each terminal on the pressure switch connector, then touched the leads of my multimeter to each and got no continuity, would that not indicate a problem with the connector?

In case this helps, I have continuity when placing the red lead in either connector terminals and the black lead on the negative battery post.

Would the fact that the blue/white wire has both continuity and voltage mean that everything is working from the ECM/PCM all the way to the pressure switch connector?

ezone

No, and you need to be careful what you stuff into any terminals as even a paper clip could be fat enough to cause a small female terminal to lose its spring tension.
Small paper clips are usually OK but big ones are not good for this.
I've been known to hammer a paper clip a bit flatter on the end so it isn't so fat.

Blue is grounded with the AC on so the HVAC control panel is doing its job. This is the "AC request" circuit and it goes through several stops before it gets to the PCM.
The PCM is in charge of the compressor clutch and fans.

Pressure switch (I assume?) has continuity, it's doing its job.

Therefore when you plug the connector onto the switch, the blue/white wire becomes grounded.

You are supposed to find the same blue/white wire testing as ground at the fusebox F#9.

This circuit and all the components is the "AC request signal" and next in line is the MICU (multiplex unit, much like a body controller on other car brands). The MICU should then pass the request signal on to the PCM.


Does the car have other odd electrical problems? The MICU can cause a lot of issues when it goes bad, AC is just one of them.


No not the PCM, because it is not the next 'rung of the ladder' or 'next in line'. In this case the next is the MICU.


Refer to a wiring diagram on this.
The path should be

HVAC panel AC request (blue wire) --> Pressure switch--> (blue/white wire) --> MICU/fusebox-->(yellow wire) --> PCM.

PCM then decides if it is OK to operate the compressor and fans.

user 84948

Okay, I connected the pressure switch connector and here are the next round of readings.

F9: 12V with ignition in "ON" position (AC on or off), and 4-5V with ignition in "OFF" position

E10: 6.2V with ignition in "ON" position (AC on or off), and 11-12V with ignition in "OFF" position

E24: 6.2V with ignition in "ON" position (AC on or off), and 11.5V with ignition in "OFF" position

ezone

Engine running?

user 84948

No, the book said just ON position so I didn't think to start it.

EDIT: by the way, to answer your question earlier. A couple of things that I noticed that don't work.
1. Door locks don't work (nothing happens when I press power lock on door panel).
2. Dome light doesn't work when in the "only on if door open" position. It turns on when in the ON position and turns off in the OFF position.

ezone

Ok. I wasn't sure if it would work as expected with the engine not running.


This should be ground.
What does the book say to do now?


Is your meter black lead connected to ground for this? Dash frame?

Pressure switch connector fully seated and locked on?


If you jumper a ground to it (F#9), will the AC compressor come on?

user 84948

By the way, I just made an edit on post #14 since you responded.

When I was inside the cabin testing terminals, for the black lead I was using one of the bolts that holds the door to the car. It was one of the only things I saw within sight that made the continuity test beep for me.

Pressure switch connector is fully seated.

The books steps were as follows:


TEST 1:
1. Disconnect the A/C pressure switch 2P connector.
2. Turn the ignition switch ON (II).
3. Measure the voltage between the No. 2 terminal of
the A/C pressure switch 2P connector and body
ground.

Is there battery voltage?
YES - Go to step 4.
NO - Go to step 10.


TEST 2:
4. Turn the ignition switch OFF.
5. Check for continuity between the No. 1 and No. 2
terminals of the A/C pressure switch.

Is there continuity?
YES - Go to step 6.
NO - Go to step 12.


TEST 3:
6. Reconnect the A/C pressure switch 2P connector.
7. Disconnect the heater control panel connector A
(14P).
8. Turn the ignition switch ON (II).
9. Measure the voltage between the No. 4 terminal of
heater control panel connector A (14P) and body
ground.

Is there battery voltage?
YES - Check for loose wires or poor connections at heater control panel connector A (14P) and at the A/C pressure switch 2P connector. If the connections are good, substitute a known-good heater control panel and recheck. If the symptom/indication goes away, replace the original heater control panel.
NO - Repair open in the wire between the heater control panel and the A/C pressure switch.


TEST 4:
10. Make sure the A/C switch is OFF.
11. Measure the voltage between the No. 9 terminal of
under-dash fuse/relay box connector F (12P) and body ground with the under-dash fuse/relay box connectors connected.

Is there battery voltage?
YES - Repair open in the wire between the under-dash fuse/relay box and the A/C pressure switch.
NO - Refer to the multiplex control system (see page 22- 268).


TEST 5:
12. Check for proper A/C system pressure.

Is the pressure within specifications?
YES - Replace the A/C pressure switch.
NO - Repair the A/C pressure problem.


Because I had voltage to the blue/white terminal, but could not get continuity between the two connector terminals, I went to step 12 and assumed bad pressure switch connector.



I will try jumping ground to F9 tomorrow when I have daylight again. I assume that I just place one alligator clip end of a wire to the negative battery terminal (or even that same door bolt) and the other alligator clip end to the paperclip (small) pushed in the wire-side of F9?


*********EDIT********

I guess It would be wise for me to check for voltage on terminal E18 from the PCM. I'm assuming we are getting a good connection from the ground on the heater control panel all the way power on the PCM inside terminal E24. I guess once it receives that current is established it is supposed to switch on the grounds that go out of terminals E18 & B6 going to relays.

By the way, I just uploaded a PDF of the circuit diagram I am referencing in case it is slightly different than the one you are using.

Link: https://drive.google.com/file/d/0B1f...ew?usp=sharing

ezone

You may have a MICU problem here.
AC request can be inhibited by a bad MICU.


I really hate they don't bother to give wire colors for testing.


You can't get continuity between the two wires if one has 12v and the other has ground.

You SHOULD have continuity between the 2 terminals in the switch if the system has sufficient pressure in it.

Using a paper clip as a jumper between the two terminals in the harness connector would simulate a properly operating pressure switch (switch contacts closed, or continuity).
I thought you did that and the system did not come on??

What's your next step here?

----------------------------------
Anyway...

Tests they have you do just look backwards to my thinking. They are having you check for voltage (bias) coming from the control unit end of the line (PCM and MICU), where instead I test for the request signal (ground) that starts at the HVAC control panel.
Similar results obtained, but totally different method and thinking.



My thinking and basic method:
(Follow the wiring diagram to see which connectors and terminals are involved.)

Known: The HVAC panel grounds the blue wire when the AC button is turned on, so I turn the system on and check:
Is that ground found going into the pressure switch? (if yes, the hvac panel is deemed ok without having to remove it)
Is that ground found going out of the pressure switch?
Is that ground found going into the MICU?
Is that ground found going out of the MICU?
Is that ground found going into the PCM?

At whatever point I don't find ground, the break in the chain should be between here and the previous test point.
I SHOULD be able to manually supply ground (at whatever point ground is missing) and make the system come on.

user 84948

The troubleshooting steps had some pictures to illustrate which terminals to check and in step 3 it was referring to the blue/white wire. ALSO....you were so right, the continuity check was on the pressure switch, not the pressure switch connector. I really missed that one.

So....
1. ground from HVAC panel: check (since continuity was established between the blue wire terminal on the connector and the negative battery post once the AC was turned on)
2. pressure switch: check
3. ground to and from MICU: check
4. ground going into PCM (E24): check

So far since we have continuity and voltage at all those points I mentioned earlier, then we can say those are good.

Would next steps be to check voltage coming out of E18 then the terminals on the relay box (moving up the ladder)?

Side question about the ECM/PCM shown in that circuit diagram I posted: inside of E24, there is a 12V power source which goes through a resistor and connects to a ground inside the PCM. What are the symbols in between the resistor and the ground symbol (the one inside the PCM...not the ground at the Heater Control Panel)?

ezone

This is screwy. So are the readings in post 12.

You keep saying "voltage".
If you are testing for the wire(s) having continuity to ground throughout the circuit, AND they are all grounded, how can you say there's voltage? What voltage are you reading?


The diagram looks about right just drawn differently from mine.

PCM terminals E18 and B6 should be turned on when the PCM receives ground on terminal E24 (yellow wire).

So try this?
Key on, all wiring connected to the PCM:
Attach a long wire to battery neg terminal (clamp it on with vise grips??)and attach paper clip to the other end....run it to the PCM, use paper clip to contact the back of the yellow wire terminal E24 and see if the radiator fans come on.
If the fans run, the compressor clutch should also click on at the same time.

This would prove the PCM is able to run those items.

If they do not turn on, then unplug the PCM connectors and ground E18 and B6 to see if each turns on its respective item, fans or clutch.



In the shop, I would have my scanner connected reading live PCM data which shows the AC request and AC clutch states. If I see the request says ON, I know everything from the HVAC control panel to the PCM is ok. The PCM has the ability to halt AC operation under some circumstances, such as overheating and large throttle opening (high TPS reading).

user 84948

For theses readings I would stick the positive lead on the paperclip inserted on wire-side of connector, then black lead would be on body ground (in this case the bolt that holds the door to the body). I put the multimeter in DC Voltage and measured the voltage coming from the terminal. I also left the leads in the same place and switched multimeter over to Continuity check (the one that beeps) and it did beep. By doing voltage test (which is what the book asked me to do), wouldn't that prove the terminal was grounded, as you need both power and ground to have current?

If I'm checking for ground wrong, how should I do it?


I will give this a shot!

user 84948

Okay, here are the results of the other tests.

1. Grounded the wire-side of the E18 terminal on Connector E to the PCM. Turned ignition to "ON" position. Nothing happened.
2. Unplugged Connector B to the PCM, stuck a paperclip in terminal E18 (going to clutch relay) and grounded. Turned the ignition to the "ON" position, it looks like the clutch is engaging (I'm not sure since I've never seen a clutch engage, but it closed the tiny gap between itself and the pulley. I couldn't start the car to see if the compressor would come on since I can't start the car without Connector E plugged into the PCM.
3. Plugged Connector E back into PC and unplugged Connector B, stuck a paperclip in terminal B6 (going to fans) and grounded. Turned the ignition to the "ON" position, and both radiator and condenser fan come on.
4. In case I wasn't probing the wire-side of E24 correctly in Test #1, I took the connector off the PCM and held the paperclip (clipped to wire running to negative battery terminal) to the pin that connects to terminal E24 on the connector. Turned ignition "ON"...and nothing.

Based on these tests, it looks like the fault is within the PCM? What do you think?

Even though it looks like the clutch can engage the compressor, I want to see the compressor run. How could I jump the compressor?

ezone

The voltage reading was what? 0v or 12v?

If the test shows a wire has continuity to ground using the ohm scale, that should mean the wire is grounded.
If you immediately flip the meter to read voltage you should see zero volts.

The next post more or less answered most of what I was wondering though.
I'd like to know if having the engine running makes any difference in this check.

Also see the comment further down.

So both items should work.

SOUNDS accurate so far, but this seems like an unusual failure to me.
This is where I need to know what the computer is thinking.
Is it even detecting the AC request?
Is it turning the clutch relay and fan relays on? Does it BELIEVE it turned them on?
Is it inhibiting AC operation for some reason? (request=yes, but command for relay=no would mean the PCM is keeping it shut off for some reason)
Why would it do that?
Any check engine codes? Temp sensor problems?





One more check:
Connect voltmeter to battery negative and E24.
Set to volts.
Run the engine.
Turn the AC system on and off using the HVAC control panel.

What value does the voltmeter show when you turn the AC on?
What does it show when you turn the AC off?


I'd say to ground E#18 with the engine running to turn on the clutch relay and engage the compressor, but you have to be careful and don't run it very long. You can cause other problems because the fans won't be running.

user 84948

First off, it probably doesn't help you when I rush and have typos giving you bad data. I have corrected my last readings in bold below.

1. Grounded the wire-side of the E24 terminal on Connector E while plugged into the PCM. Turned ignition to "ON" position. Nothing happened.
2. Unplugged Connector E from the PCM, stuck a paperclip in terminal E18 (going to clutch relay) and grounded. Turned the ignition to the "ON" position, it looks like the clutch is engaging (I'm not sure since I've never seen a clutch engage, but it closed the tiny gap between itself and the pulley). I couldn't start the car to see if the compressor would come on since I can't start the car without Connector E plugged into the PCM.
3. Plugged Connector E back into PCM and unplugged Connector B, stuck a paperclip in terminal B6 (going to fans) and grounded. Turned the ignition to the "ON" position, and both radiator and condenser fans come on.
4. In case I wasn't probing the wire-side of E24 correctly in Test #1, I took the connector off the PCM and held the paperclip (clipped to wire running to negative battery terminal) to the pin (on the PCM) that connects to terminal E24 on the connector. Turned ignition "ON"...and nothing.

The voltage was never 0v on any of the terminals I checked. Post #12 had the voltage readings, here they are:

Connector Terminal F9: 12V with ignition in "ON" position (AC on or off), and 4-5V with ignition in "OFF" position

Connector Terminal E10: 6.2V with ignition in "ON" position (AC on or off), and 11-12V with ignition in "OFF" position

Connector Terminal E24: 6.2V with ignition in "ON" position (AC on or off), and 11.5V with ignition in "OFF" position

Do my corrected readings above still make you curious?

Makes sense....I guess kinda hard to know all this without an expensive scanner? Will the ~$200 OBDII scanners do this?


If my corrections up top don't make any difference in your thoughts on next steps, I'll go ahead with checking the voltage on the E24 connector terminal and for kicks I'll try grounding the E18 connector terminal (assuming it doesn't kill my PCM) and start the engine/AC for a brief minute.

ezone

1,2,3,4 made sense before the corrections LOL

I guess starting the engine in step#1 wouldn't matter much,

but I still want to know what the volt readings are at PCM E#24 as you turn the AC on and off with the engine running. This SHOULD confirm the request signal made it to the PCM


--------------------------------------------------------

My problem with what you say is voltage is this:

A grounded wire cannot also have voltage, unless the test condition changed or wire is not truly grounded.
...
Ummmm, thinking about that---maybe I see why your test results looked screwy to me.

Ok a few thoughts about using a volt-ohm meter:

Are you going by a beeper function to determine continuity instead of looking at the ohm value? A beeper might sound off even though the meter is a bit higher than zero ohms. I had one that would beep up to about 200 ohms.

Meter functions can also be misleading, using ohm scale to check anything that could have voltage running through it can throw your readings off.


Examples:
If you connect your black meter lead to neg battery post and red lead to the door bolt, what does your ohm meter read?? Probably close to zero ohms?
Now turn the key on, does your ohm meter reading change?

Turn key off.
Now connect the red lead to something metal on the engine, like a bolt on the alternator mount.....Meter reads close to zero ohms? Start the engine and see what happens while it is cranking, and then see what happens as the alternator starts charging.

----------------------------------

Likewise when testing voltage, a grounded wire might show as zero volts--- but an open (disconnected) wire could also show zero volts.

This is a good reason to flip the meter back and forth to ohms just to make sure the wire is really connected to something on the other end. If it reads infinite resistance I would suspect the wire is not connected at the other end.

Are you now using the wire solidly attached to the battery neg post as your ground lead connection point?

Quote:

Makes sense....I guess kinda hard to know all this without an expensive scanner? Will the ~$200 OBDII scanners do this?

Sorry I can't answer that, I am not familiar with what is available through the aftermarket.
I use Hondas HDS scanner.

user 84948

I stuck a paperclip in the wire-side of the E24 connector terminal and got these readings:

1. With ignition in "OFF" position and AC also off, I got a voltage reading of 6.5v
2. With ignition in "ON" position and AC also off, I got a voltage reading of 7.5v
3. With ignition in "RUN" position (engine running) and AC also off, I got a voltage reading of 7.5v
4. With ignition in "RUN" position (engine running) and AC on, I got a voltage reading of 7.5v

So it didn't make any difference if AC was turned on or off at the HVAC control panel.


I ran a cable from negative battery terminal and connected to paperclip in wire-side of the E18 connector terminal. When I started engine (AC off on HVAC control panel), the compressor started running (saw clutch engaged and spinning). Turned AC on through HVAC control panel and the air blew a little cooler than usual (not cold granted). I didn't leave it running long enough to get pressure readings from the High and Low ports on the HVAC lines.

ezone

Which troubleshooting steps lead you to check the yellow wire from the fusebox to PCM??

(referring to test 4 in a previous post)

ezone

I think you need to check multiplex functions, self test for fault codes and in/out checks.

user 84948

I am not sure how to run this self test on the MCU. However, I think you might be right, I just came across this video where a honda civic owner replaced his MCU because of the exact same issues (some of them I didn't even notice yet as I've only had the vehicle 5 days) as me. AC not working, key chimer not working when door is open, dome light not staying on when door open, brake light on all the time, remote door unlock not working. I have all these symptoms.

Watch this video and go to 11 minute mark (he describes issues he had with the bad MCU).


-----------------------

I also went out and rechecked all these connection points (sorry for some of the useless data, I just wanted to record everything). It looks like I have ground from the Heater Control Panel all the way to terminal F9 on MCU, but then nothing going out of E10.


AC Pressure Switch Connector - Blue Wire
Red lead on blue wire terminal on pressure switch connector and black lead negative battery terminal:
1. Ignition in ON position and AC switched off: 12.5 on Ohms 200 setting. 0 volts.
2. Engine running with AC switched off: 1 (infinite) on Ohms 200 setting. 0 volts.
3. Engine running with AC switched on: 5.5 on Ohms 200 setting. 0 volts.

AC Pressure Switch Connector - Blue/White Wire
Red lead on blue/white wire terminal on pressure switch connector and black lead on negative battery terminal:
1. Ignition in OFF position and AC switched off: 1 (infinite) on Ohms 200 setting. 4.8 volts.
2. Ignition in ON position and AC switched off: readings were empty (assuming infinite) on Ohms 200 setting. 12 volts.
3. Ignition in ON position and AC switched on: readings were empty (assuming infinite) on Ohms 200 setting. 12 volts.
4. Engine running with AC switched off: readings were empty (assuming infinite) on Ohms 200 setting. 13.5 volts
5. Engine running with AC switched on: readings were empty (assuming infinite) on Ohms 200 setting. 13.5 volts.

Terminal F9
Red lead on F9 connector wire-side and black lead on negative battery terminal:
1. Ignition in OFF position and AC switched off: 1 (infinite) on Ohms 200 setting. 4.9 volts.
2. Ignition in OFF position and AC switched on: 1 (infinite) on Ohms 200 setting. 4.9 volts.
3. Ignition in ON position and AC switched off: readings were empty (assuming infinite) on Ohms 200 setting. 12 volts.
4. Ignition in ON position and AC switched on: 18.5 on Ohms 200 setting. 0.02 volts.
5. Engine running and AC switched off: readings were empty (assuming infinite) on Ohms 200 setting. 13.3 volts.
6. Engine running and AC switched on: 14 on Ohms 200 setting. 0.02 volts.

Terminal E10
Red lead on E10 connector wire-side and black lead on negative battery terminal:
1. Ignition in OFF position and AC switched off: readings were empty (assuming infinite) on Ohms 200 setting. 11.5 volts
2. Ignition in OFF position and AC switched on: readings were empty (assuming infinite) on Ohms 200 setting. 11.5 volts
3. Ignition in ON position and AC switched off: readings were empty (assuming infinite) on Ohms 200 setting. 6.6 volts.
4. Ignition in ON position and AC switched on: readings were empty (assuming infinite) on Ohms 200 setting. 6.4 volts.
5. Engine running and AC switched off: readings were empty (assuming infinite) on Ohms 200 setting. 7.4 volts.
6. Engine running and AC switched on: readings were empty (assuming infinite) on Ohms 200 setting. 7.4 volts.

Terminal E24
Red lead on E24 connector wire-side and black lead on negative battery terminal:
1. Ignition in OFF position and AC switched off: 1 (infinite) on Ohms 200 setting. 0 volts.
2. Ignition in OFF position and AC switched on: 1 (infinite) on Ohms 200 setting. 0 volts.
3. Ignition in ON position and AC switched off: 1 (infinite) on Ohms 200 setting. 6.8 volts.
4. Ignition in ON position and AC switched on: 1 (infinite) on Ohms 200 setting. 6.8 volts.
5. Engine running and AC switched off: 1 (infinite) on Ohms 200 setting. 7.8 volts.
6. Engine running and AC switched on: 1 (infinite) on Ohms 200 setting. 7.8 volts.

Terminal E24 - female side of connector
Unplugged Connector E from the PCM. Red lead on E24 connector (female side) and black lead on negative battery terminal:
1. Ignition in OFF position and AC switched off: 1 (infinite) on Ohms 200 setting. 11.5 volts.
2. Ignition in OFF position and AC switched on: 1 (infinite) on Ohms 200 setting. 11.5 volts.
3. Ignition in ON position and AC switched off: 1 (infinite) on Ohms 200 setting. 7.3 volts.
4. Ignition in ON position and AC switched on: 1 (infinite) on Ohms 200 setting. 7.3 volts.
5. Can't start engine with connector E unplugged from PCM so can't run readings with engine running.

ezone

The request signal got to the fusebox (MICU).



Uhh, video fail. No biggie, I know what it looks like.
I mentioned many of those symptoms much earlier in the thread, post 9 and maybe a few others.

Also for your viewing pleasure, I may be an idiot and that's what I get for assuming. I was looking in a few of the trouble charts and did not find any mention about testing nor what is to be found on the yellow wire.....under AC symptoms. It only references performing self tests on the MICU.....So it must be a communication line to the PCM that may carry data instead of a simple on-off state.

Look in your manuals under body electrical, pick something that doesn't work like the dome lights or power locks, see if those lead you to testing the multiplex system in mode 1 and mode 2.

user 84948

Uh, yeah..it's like when I mean to attach something to an email and don't...


Anyways, I will follow that lead and check the remote door locks or dome light or key chime. I'll let you know what I find.