dabatman99

I've been looking for a 2004-2005 wiring diagram that helps explain what is going on with my car. This all started with a P0135 code which led me to check the voltage for the heater circuit. There is no voltage. I have another 2005 civic and checked that and there was over 8 volts dc. Apparently there is A/F Heated Sensor Relay located behind the glovebox. I checked it out and seems fine, and I even swapped it out with the known good car. Still no voltage. All I could find online were wiring diagrams from a 2001 to 2003 civic, but that is a whole different system (narrow band O2 sensor). Maybe I'm totally in the wrong area, but if anybody can help, I really appreciate it. Oh ya, and I started all of this by changing to a brand new DENSO O2 sensor but of course the new one doesn't work because the heater circuit is not getting any voltage. thanks guys

mac25

Not sure how you tested the voltage...

did you test it pre-sensor or post-sensor?

Pre-sensor would indicate that there is a brake in continuity, fuse, relay, wire, ecu problem.

Post-sensor, it may be the sensor.
If you have two 2005 civics swap the sensors from one car to the other and see if the issue transfers to the other car, if so the sensor is obviously the issue.

dabatman99

I tested it at the sensor connector ( from the ecm). And i instapled a brand new denso o2 sensor.

I was able to confirm the wiring is good between the ecm (green wire) and the a/f heater relay ( white wire) both have continuity...howerver the white wire is supposed to have battery voltage ( when relay is activated) and green wire is the switched ground. These wires are contolled by the ecm directly and apparently its not doing its job. Im begining to think that the ecm is faulted and might need replacement. Next step i guess is to swap ecm from other car and see what i can come up with.

emich

You didn't set up your millimeter on Ohms checking voltagedid you?


That's what I did by mistake about a year ago providingvoltage to the terminals. It's a sure way to blow off resistor inside the ECU. It tookweeksto figure it out.

dabatman99

I only checked voltage on the plug from the ECM. I was expecting 8 to 12 volts DC and got 0 volts. Did you change out ur ECM? Do you have a procedure, or know the steps needed to swap one out? Does it need to have the exact model?

ezone

PCM turns on the heater relay, and that relay feeds power to the sensor when the PCM turns the relay on. (I think the engine has to be running first.)

PCM only controls the ground to the heater, and I'm pretty sure it will not turn that on until the engine is running.


Google found this diagram, it looks pretty close but I did not thoroughly inspect for accuracy

dabatman99

Thank you, I did end up finding same diagram as well. I can confirm that there was positive battery voltage going to the relay, but there was no negative (or ground) on the control side of the relay (see the ORN wire going to E8). Looks like the ECU is not activating the E8 circuit, thus not allowing a current path to flow in order to activate the heater relay. I did jump a ground wire to the relay to get it to activate. I then watched my scan tool graph (it was monitoring the signal coming from the O2 sensor); however there was no activity. Not sure where to go now except for a possible ECU swap. Does anybody know if the ECU's are repairable or should I be looking for a used replacement.

ezone

There are several places that claim to repair PCMs but I've not gone that route in several years. Inquire with your local big name parts stores or google and check reviews first

If you go with a used PCM the immobilizer will need to be programmed before the engine will run. (you may get an ignition/column lock assembly and PCM as a matched set, that should run the engine without dealer programming but will make you have extra keys and it's extra work)


EDIT: Depending on the time required to trigger a fault code, you might have like 5 seconds (or less) to test for operation of that circuit. Some cars set the code in 5 seconds....then probably shut the heater circuits off so you only have a very short time to test.
Other cars may take up to a minute to set a heater code.

dabatman99

Would you know if I got a used ECU, would one from a 2004 to 2005 out of an automatic vehicle work in my car? My car has a manual transmission. Or does the part number of the ECU match exactly?

ezone

It needs to match a helluva lot closer than that.

An auto trans computer may run the engine but it will set codes for every part of the transmission it can store.

Major differences are usually, but not limited to:
Engine size/code
VTEC or not
Trans type
Trim level
Emissions type
Your country may make a difference too


You can use an online parts catalog and enter your VIN instead of choosing the options to look up a correct computer part number

dabatman99

You know what, the ECU part number is 37820-PLM-C08. When I looked that up online, it came up as an ECU for a 2003 civic. Is it possible that the guy I bought the car from might have had the ECU changed, and this is why the O2 sensor doesn't work? From what I see online, it looks like I should have either a 37820-PLM-C13 or c14. If I could just confirm that the PLM-C08 is actually from a civic prior to 2004, then that would solve everything!

ezone

Those 3 part numbers didn't turn up search results in my catalog. Are you in Canada, or was this car built for sale in Canada?


If it is actually an 03 ECM, it cannot work correctly with 04-05 car because of the differences in the primary sensors (O2 vs. AF) and that one relay that operates the heater circuit. There may be other reasons too but that looks like the one you're dealing with now.

emich

Hold on with swipe. Open the ECU and look for damage like burned resistors.
If that's the case it is easy fix just solder iron on top new ones. I did that on mine.

dabatman99

I got a chance to open up the ECU and looked for anything burnt or suspicious, and it all looked really good. I did notice that there was some writing on it (from a marker) in handwritting. I didn't pay too much attention to it, but got me wondering if that was a junkyard identification number? Anyways, I am in Canada, and the car is canadian. And I agree if this is out of a 2003 civic, then that explains why the O2 sensor isn't working properly. According to the drawing that you provided, it seems that I might be able to change the wiring ground from A16 to A10, and permanently jump out the relay or bypass it all together so the setup is similar to the 2003 setup. What do you think? I'll have to try to find a narrowband O2 sensor, but I think it's worth a shot.

ezone

I never considered trying to convert a system to match or work with a wrong ECM.

Do you have to pass an emissions test there?

dabatman99

No emissions here yet! shhh! lol So I was able to confirm on Toronto Honda Parts online website, and the 37820-PLM-08 is from a 2003, and my 2005 is supposed to have one of the following:
37820-PLM-C11
37820-PLM-C13
37820-PLM-C14
37820-PLM-C15

From what I gather up, it seems that the 2001 to 2003 civic did not have an EGR valve. My car does have one. So I could try using the older style O2 sensor like I mentioned earlier, or I can get the correct ECU (for about 100.00) and then get it flashed (not sure what Honda charges could be over 100.00). Besides emissions, what other benefit is there with an EGR?

dabatman99

Just to clarify a bit, I bought this car a few weeks ago, and the guy who had it didn't know much about it. It has low mileage, but Im thinking he might have had issues with car, and decided to swap ecu and instrument cluster from a 2003. I could have been scammed.

ezone

I'd say to just get the correct ECM and be done with it.
Saves headaches now, and later on for the next owner too.


The cluster was swapped too? You sure of that?

Do the door and ignition use two different keys?


The most frequent PCM (ECM) failure in the 01-05 cars is usually caused by someone leaving the alternator bolts loose during a service. Otherwise, they seem fairly bulletproof.

dabatman99

I actually got the correct ecu from a junkyard. Need to get it flashed. Apparently its 90 bucks plus tax to get it done. Do you know anything about a "SBB V33 key programmer Silca SBB V33.02 immobiliser programmer" that i found on ebay? would this actually do the same thing as the dealer?

ezone

Made in China....beware.

It looks like it would do ordinary key programming ..

..but you would need to be able to marry the immobilizer control unit to your new PCM and I can't tell if it would do that.

Need more info I guess or look for reviews. Locksmith forums?

ezone

I assume it would but I can't say for sure.

dabatman99

I'm going to bite the bullet and take it to the dealership on wednesday to get the ECU flashed and get the airbag recall done on it too. I was a bit uneasy spending money for the programmer and it not doing what I want it to do. Nothing I'd hate more than to spend money on a programmer, then spend another fist full of money to the dealership. Looks like they win again! LOL As long as this new ecu works, then the O2 sensor should work again, and also the EGR system. Cross your fingers! Thanks for all your help.

dabatman99

Well went to the dealership. They replaced and programmed my new ecu. Car starts fine. Now I'm havine a P0404 code (EGR), and P0420 (catalyst), and now the signal from the O2 sensor is not displaying on my scan tool, but there is no code for it. Been driving it that way since yesterday. I'm going to have to try to measure the voltage coming from the O2 sensor and see if it is actually working (it is a brand new denso). The egr might need cleaning as well. I'm thinking I've solved some problems, now have to solve some more.

ezone

P0404, EGR valve insufficient lift. That means the computer did not see it open when commanded.
If it's been unused for a long time (due to wrong ECM) it may just be stuck closed.

P0420, typical. It couldn't show before because of the O2 sensor fault. Now that it has a working sensor with no related fault, the computer can run the cat testing as you drive....and it apparently failed.
I'd erase the code and see how long it takes to return.

IDK what you are using as a scanner, but sometimes aftermarket stuff can be flaky, some can't even report fault codes accurately. People post here from time to time with codes that are impossible to have on the car they drive.

dabatman99

Thanks for your response, I appreciate it. I did take out the EGR valve and it was sooty, and cleaned it up with carb cleaner. I was able to pull out the valve with a pair of needle nose pliers to spray some cleaner in there as well. I might try swapping the egr valve with my sons car this weekend when I get time. As far as the O2 sensors are concerned, the primary is flat-lined at 0.0V and the secondary is bouncing around usually between .6volts and .4volts, and almost looks like an irregular heartbeat on my graph of my code scanner. I've got to take some voltage measurements of the primary sensor to see if it is actually working properly. I am thinking that if it is working then it's in a hard "lean" condition; otherwise, I might be able to assume that the sensor input to the ecm could be bad. More troubleshooting and investigation is needed for sure. I'm working shift right now so it's hard to get time to actually work on it. At least the car is running fairly good, and I can't complain too much about it except I think its still a bit harder on fuel than my son's 2005 honda civic (Same car as mine but his is a DX and mine is an LX). Thanks!

BTW I'm using a generic bluetooth code scanner that I got on ebay. It seems to work fairly good.

ezone

Don't f*** with the sensor.
Your primary sensor is NOT a plain O2 sensor, it's an AF sensor. Huge difference.

They look the same, smell the same, they do about the same job, but operate completely differently and cannot be interchanged. The computer and programming are quite different as well, it cannot use a plain O2 sensor as a primary.

Because AF sensors operate differently from an O2 sensor, you will not read the same values in the data.
The PCM works to keep the sensor value steady. You won't see it fluctuate hardly at all until you accelerate or decelerate rapidly. A snap throttle should give some sort of change in the sensor reading, then it will go back to steady at idle.

If it's not causing a fault code just assume it's OK.


You got the EGR cleaned, is it still setting the P0404 code now?

dabatman99

I'm very much aware of the differences between the two styles of O2 sensors. When I say the primary sensor, I'm referencing the A/F sensor (wideband sensor). It is at 0.0V steady no matter what I do. But there is no code for it. So it could be my code reader thinks it's a generic narrowband O2 sensor...i'm not sure. Still investigating that one.

The EGR was cleaned and put back into service but is still giving the P0404 code. I'm going to try to swap it with my son's egr from his car (2005 honda civic dx) and see if it is really defective or not.

I also got a P1457 code "Leak in EVAP" and could be a multitude of things from gas cap to a leak in a line to a problem with the "vent-shut valve" on the canister. I'll have to figure that one out too.

When I got the P1457 I also got a P0303 code (cylinder misfire #3), so they might be related. Or they might ALL be related to the EGR valve.

ezone

My scanner reads AF sensor in milliamps, not volts. See if yours is too.
Watching a 13 Accord on my scanner right now, it's AF sensor is quite steady reading at 0.00-0.03 mA @hot idle.

P0404, I might try to see if the ECM is actually capable of aqpplying power and ground to the egr valve. If it isn't opening for whatever reason, the P0404 sets. No appropriate response (from the position sensor) to the commanded opening.

P1457, canister system, not fuel tank. That should at least rule out most of the gas tank parts and gas cap.
Are you in the rust belt?


Misfire...got freeze frame data and does it go with this code?
If the EGR is not operating, it can't cause the misfire code. HOwever, if it does work and it set that code during steady speed driving, egr is possibly related (clogged ports and passages in the distribution plate).

dabatman99

I have a bluetooth scan tool that I bought on ebay, and I was using Torque Lite on my android phone. It seems it only reads volts when it comes to O2 sensor Bank 1 Sensor 1. So I upgraded to the pro version for an extra 6 bucks, and this actually measures the "O2 Sensor1 Equivalence ratio", which ideally should be 14.7:1. My actual feedback on the graph showed it to be very stable and looked to be very very close to the 14.7:1 ratio, and when I accelerated or decelerated it did change a bit, but quickly went back to the normal value when I resumed normal driving.

Tonight I'll try swapping the EGR valve with my sons car and see what I find there. I did buy an intake manifold gasket kit, and will probably end up taking off the intake and doing a thorough cleaning of the egr passages IF I find that there is nothing wrong with the EGR. I hate throwing parts (parts = money!) at problems.

The P0420 code still coming up, but waiting to see the results from the EGR. I've been monitoring the downstream O2 sensor and it isn't steady like the upstream, but bounces up and down (generally around 0.6mV +/- 0.2mv). I do have a replacement O2 sensor (Denso) that I can put in and try before I would rule out the catalytic converter as being bad.

You mentioned if I lived in rust belt area...OH YA do I ever! But with the P1457 code, I'm not too worried about that at the moment. I'll try to hit these bigger problems first then deal with that after. I believe that code is on my son's car too. Doesn't affect mileage or performance, but CEL light is always on!

ezone

P0404 cannot be caused by clogged passages, so I would not go into the manifold yet.

You should be able to use 2 jumper wires to manually open the egr valve....see service info and wiring diagrams


on your scanner app is there any data telling about commanded or desired egr position?
How about actual egr position?