1996 Accord 2.2 No ground from ECU to O2 Sensor
 

Hello folks! My 1996 Accord 2.2L is throwing a P0135, O2 Heater Circuit, Bank 1. I am getting 12 volts to the O2 Sensor, but NO Ground. I traced the ground wire, (Orange with Black stripe), to the ECU and the wire reads out as good. There is No Ground coming from the ECU into that wire. (Key in the ON position should produce a ground). Rather than replace the ECU, does anyone know if I can just splice in another ground to that wire, so the Sensor can function? Or would that damage the ECU? Ground is ground, right? The only difference is that the wire would be grounded even with the car off.


Mucho appreciation for any feedback !!!

Did you get 12V when meauring voltage between Orn/Blk (PCM ground) and Yel/blk (12V supply) on the engine harness side of O2 connector? If this measurement indicates 12V, suggests the PCM ground is OK.

If you measured resistance between harness side grn/blk and local ground you could be fooled by length of ground path.

Only way to be sure is to measure ground at the PCM pin A11.

good luck

I did NOT get voltage when reading between the org/blk and yel/blk. However, I did get voltage on the yel/blk when I checked it using body ground. then I checked the org/blk against body/engine continuity, and, nothing. Lastly I checked the org/blk using battery Positive for voltage flow. Nothing.


Thank you for the info. Can I assume that pin A11 is the ultimately the org/blk wire? Also I had read that this ground wire Only receives ground through the PCM with the key 'ON' ?


I did confirm this ground wire is Good all the way up to the PCM.
Lastly, I snipped the ground wire on the Harness side and added my own ground. No change. Although I have cleared the code a dozen times, it returns within 5-7seconds of engine running.

The primary heater control Orn/Blk wire is connected to the ECM/PCM at pin A6. Yes, it should have ground with ignition switch in "ON".

Pin A11 has a Yel/Blk wire and is the power input (+) to the ECM/PCM. It comes from under-hood fuse No. 33 via the main relay; it is not a ground signal from/to the ECM/PCM.

Yes, I clearly understand that, and thank you. The bottom line is I have NO ground coming out of the ECM/PCM to that Org/Blk wire, therefore the O2 Sensor Cannot function, and why it keeps coding. I even tried adding my own Body Ground to that wire, but no difference. I think the issue is in the ECM/PCM.

How did you verify the orn/blk wire is good from the O2 sensor to the PCM?

Sorry for my 'outta town' delayed response. I did a standard continuity test. ( I used to do electronic repair on Navy F-14's for 4 years, followed with auto repair for 30 years). Heaven forbid I screwed That simple test up, oh God, lol !

I sold the car to a friend who figured he could resolve the issue. I felt I could go no further anyway, (and loosing big $$$ on other jobs). Besides replacing the PCM, I was at wits end.( I feel ass kicked, a rare thing indeed). The bummer is that I cannot post the repair to the mystery, ... yet.
Sooo much gratitude for this forum, for the experience, wisdom and caring of YOU who have replied. I feel honored and blessed.
Mucho Gratitude, Hondaddy