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I am about to pull my head out, all of the searching and Ideas I have found amount to nothing....

I am working on a 2004 Honda Civic EX. CEL P0141 - P0135

I have worked through all of the following

No Voltage on White Wire of Sensor Plug

Fuse 2 Under Dash is good

Replaced A/F Sensor. (It was old anyway)

Tested Green wire to Relay - .1 ohms

Tested White Wire to Relay in front of PCM - .3 ohms

Tested Relay using 9v. Coil activates contactor in the relay.

Tested Contactor circuit in relay - 0 ohms while coil active open with coil inactive

Used Hord Relay in to test in place for posterity.

Key Off Testing
Tested Relay lead wires for voltage - White/Red Strip 12v constant

All other wires no voltage.


Key on II Testing
Coil Wires give 12v both sides

White with Red gives 12v

White gives 0V -- Issue Found

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

Pulled wires from relay socket

Connected coil wires and turned on ignition.

Relay is open--

I have tried other relays x2

all other fuse 4 things appear to be working.



What am I missing?????

 
Rep Power: 517

Got a wiring diagram for your car and this particular system?

 
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No sir. Most of what I have done is based on all of the forum searches I have knocked out.

 
Rep Power: 209

Here ya go buddy:

 
Rep Power: 517

Remember when testing, any electrical item not only needs power to operate, it needs ground too.

 
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Ok I marked up the diagrams.

First is installed normally.

Seconds Shows when I manually activate the relay.

I have tried multiple relays. All do the same thing. Key is on in each test. Voltages are my meter readings with my ground probe connected to a solid frame ground.

 
Rep Power: 517

What did I tell you about grounds?

At relay: Measure on green wire (comes from PCM E8), then start the engine and see if it becomes grounded when engine starts.

 
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Ok going now. Sorry mis read.

 
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For some reason, I get the feeling ezone's next post is gonna make me wish I cried...lol



It does NOT go to ground with engine on.

 
Rep Power: 517

Somewhere in this forum there is a thread where someone had the wires ripped out of the O2 harness connector, they shorted and ruined the PCM in the process.

Search for P0135, I think it's been within the last year or so.

 
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However that doea not answer why your pcm would not turn on the heater relay .......but I wonder if a test unit would tell you if the problem is or isn't in the pcm.

 
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So your suggestion is take it to a dealer to have it fully tested? If so I agree I am probably at that point I hate getting my rear handed to me on stuff like this.

I am traditionally a GM guy (there is a bet among my friends to who can get the first picture of me in a Honda.) I have not touched any Japanese cars since I left Japan 15 years ago with the military and even then it was always Nissan.

These little things in a Honda are gonna take some adjusting my mindset to, not bad different, just different thought processes in how I approach things. i.e. The ecu seems to be very "touchy" in a GM only time I saw a fried ecu was when someone was being really stupid.

 
Rep Power: 517

Not necessarily but maybe find another 04-05 to test on.
If it is a fried pcm, figure out what caused it so it doesn't happen again. Relay coil shorted winding?

I thought the long loved TAP TEST originated with diagnosing junk intermittent GM ECMs.

 
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True on the GM ecu. I just never experienced or saw it outside of a bad tune flash.

Thanks for help. Walking salvage yard looking now.

 
Rep Power: 517

You realize another pcm in your car will not let the engine start until the immobilizer is programmed to it...... You may need the ignition switch/keys/immobilizer ring that is in the same car as whatever pcm you find

 
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Yeah I found one with key ecu ignition door trunk and interior cylinders. Pay dirt baby

 
Rep Power: 517

Not sure how you managed to put that reply in a completely unrelated tthread.....post moved now

 
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No clue. Lol. However ecu, key, ignition, all 5 body locks in hand. Will update post test.

Again ezone I greatly appreciate the assistance.

 
Rep Power: 517

The suggestion of finding another car to test on was just to figure out what you should see while testing on yours. let us know how it turns out

 
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I just discovered something. The existing ECU is not bolted down. I am going to replace regardless due to locks currently not matching, however my mind immediately goes to is it even grounded currently. Many times things like the ecu are case grounded.

Just a thought, or am I off base totally?

 
Rep Power: 517

Grounds are wired on this one....but someone somewhere had to Unbolt it for a reason, maybe chasing this problem ....or a junker created this problem?

 
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OK so after a crazy long week, I finally was able to get in and get the test ecu/ignition hooked up to test. IT WORKED..sort of... It cleared the A/F sensor heater, the o2 sensor heater is still ther, however I have not touched that and it very well might still be bad.


THANKS ezone.

 
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Ok not sure if I should start a new thread to keep this one on topic.

I installed the ECM and lots of things have smoothed out, idle is no longer 1100-1500 bouncing. I have completed the idle relearn process and it is doing about 690-725 with ignition advance about 2-6 degrees. Good deal.

However about once a minute it drops down to about 550 it bogs down and the advance has to jump to about 12-15 degrees to prevent a stall.

I do not have the AC currently running on this so unless it is the puppy in general it isn't my first thought.

I find this a bit more difficult to diagnose with a little auto scanner.

Questions are this

1. Where should I start looking for this

2 is there a system like my HP tuner system for GM stuff that will let me dive deeper into the ECM for diagnostics than I get out of a hand scanner. I know I can't flash a Honda ecu, I am more looking for all the advanced diagnostics and graphs of every PID possible that I get out of my HP tuner for trend analysis.

 
Rep Power: 517

So someone else already replaced your PCM and ignition before you got the car? Did I read that right?

New PCM got the AF heater code to go away, but now the rear sensor code is still a problem?

I have a note saying a good rear O2 sensor heater in an 05 Civic measured 15.6 ohms hot.

 
Rep Power: 517

Make sure alternator bolts are tight. Loose bolts can cause regulator to run away due to poor grounding, that runaway voltage can burn up the PCM.


Get engine warmed up, shut it off, do a battery cable reset/reboot, then do the 10 minute idle relearn procedure with NO electrical loads running

 
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Yes it was still tripped as a bad heater, however i get 0 resistance on the heater at the actual sensor so I am betting it is actually bad.

The joys of a working ECU... my AC unit working now instead of clicking out high when I add 1/8lb and clicking low when I drop an 1/8lb. Idle is good, it sounds much better. Got a few new DTC, however I think I have them under control. 2646 and 2647, picked up a new oil pressure switch for the Vtech solenoid, also went ahead and ordered a replacement gasket set for the solenoid because although the screen was clean the actual rubber was dry and smashed flat making me worry about it sealing.

I do have this for you ezone, might make you facepalm like it did me. Since I was 10 legs into the engine and it has a noticeable valve lash sound I decided to adjust the lash. My feeler gauge set goes from .002 up to .024, only one valve actually had a gap that was less than .024 and it was .019. Needless to say the lash is in spec now.

 
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Ok the civic is doing great, almost perfect in fact. Valve noise is almost new sounding, new o2 Sensor fixed the codes for that.

Only thing remaining is the p2647. Here is what I have done so far.

New oil pressure switch
Cleaned screen and entire assembly
Replaced screen because the gasket need it anyway.
Changed oil when I replaced gasket
New filter when I changed oil
Verified continuity from ecu to oil pressure switch
Verified voltage to pressure switch

I think I am out of ideas from searching the forums.

Also I was receiving this code prior the valve lash adjustment. This is the code that led me to digging in deeper into the engine to remove the solenoid, which somehow my brain led to pull the fracken valve cover and get the lash fixed. I dunno, car time for me is peaceful lol.

 
Rep Power: 517

Was this code present with the previous PCM?

Got freeze frame data to post for this code?

Is the code reset immediately?
Erase code and get it to reset again.
Does this code set at idle (like 5 seconds after startup), or did it set at high RPM?
Did it reset without starting the engine?

How long has this code been present? Did it begin after some repair work?

What was result?
I hope that means the oil pressure switch on the VTEC unit, not the one by the oil filter.

Ohm check VTEC pressure switch. Are the contacts open or closed (engine off)?

Is the ground wire for the pressure switch actually grounded?



I'll guess the code sets 5 seconds after engine start because PCM is not seeing 0v at the terminal for the pressure switch signal, at idle Why is the PCM not seeing that?
Get your wiring diagram......?

 
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It was not present with previous PCM.

It does not set until the vehicle hits 4k rpm
I have reset it multiple times.
No it does not set at idle only at 4k rpm

It began after replacing the PCM.

Voltage was 12V to the vtec solenoid oil pressure switch on the backside of the head.

Ground side of the plug is .2 ohms.

I have not checked the resistance at this point, howeverI pulled the entire thing BACK apart and did a full blown qtip cleaning with emory cloth on anything that was discolored. Put it back in WITH A NEW OIL PRESSURE SWITCH from autozone (yes i verified it was the correct part number it was this VVT Oil Pres Switch , now it is doing the exact same thing, except now it is p2646 instead of p2647..... Me and this vtec are about to step outside and see who is a bigger man... lol

 
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Freeze frame report generated by Torque for Android
================================================== =======
Vehicle VIN: 2HGES25735H******
Vehicle Manufacturer: Honda
Vehicle Calibration ID: LRA130..........
Freeze frame information:
------------------
Fuel Status = 0 byte
Engine Load = 95.294 %
Engine Coolant Temperature = 179.6 °F
Fuel Trim Bank 1 Short Term = 0 %
Fuel Trim Bank 1 Long Term = 0 %
Intake Manifold Pressure = 14.069 psi
Engine RPM = 4,192.25 rpm
Speed (OBD) = 53.438 mph
Timing Advance = 12 °
End of report.