Mixed up o2 sensor plugs??

[DucatiCraig]

Did a tranny swap, and afterward the car ran fine except at light throttle when completely warm.

I suspected an o2 sensor connector that was swapped, and tried swapping a couple connectors. The car runs fine now, but the CEL and TCS lights are staying on.

I'm wondering if I still have some connectors wrong, if there's a better way of knowing which goes where rather than trial and error, or ???

Thanks!


- Craig

 

[Larry Bastanza]

Once you get the check light, the 02 sensors are disabled. That is why the car runs fine, it is not using them.

Get the codes to determine what issue you are having.

What year car?

Do you have headers?

HTH,
LarryB

 

[ftuhy]

Larry,

If only the heater fails on an O2 sensor, does that also disable the sensor(s)? Or are the sensors only disabled when the trouble code is for the "sensor part of the sensor"?

Just curious.

Frank

 

[davidf]

I'm curious why the car runs just fine with the 02's disabled {I've read sometimes better}. Is there any long term downside? No problems, just curious.

 

[Larry Bastanza]

Larry,

If only the heater fails on an O2 sensor, does that also disable the sensor(s)? Or are the sensors only disabled when the trouble code is for the "sensor part of the sensor"?

Just curious.

Frank

I am not 100% sure, I never correlated the heater vs. 02 out of range codes. I know anytime I have a poor running NSX under part throttle if I disconnect the 02 sensors and it comes alive they are the problem. This is the case when there is no code. I force the code by disconnecting them. As I think further, since the scenario I describe here is based on no code at all, I think the heater open would cause it to disable the closed loop mode.

I will have to pose this question to Honda, Japan.

Regards,
LarryB

 

[topgunsnsx]

I'm curious why the car runs just fine with the 02's disabled {I've read sometimes better}. Is there any long term downside? No problems, just curious.

Anyone have an answer?

 

[DucatiCraig]

Larry -

It's a 1995 with comptech headers. I'll get the codes.


Topgun -

I believe it was running poorly before because when it was in closed loop mode, (warm & part throttle operation), the ECU was trying to adjust the AF ratio to bad info from incorrectly connected o2 sensors.

Based on Larry's observation, it runs "correctly" now because it's is in open loop mode all the time because the sensors are disabled.

I would suspect that fuel economy and emmissions performance are not as good in open loop mode. I'm not sure it would cause any long term damage, other than perhaps the impact on the cats from running at the ECU's "guesstimates" of the correct AF ratio.

 

[Larry Bastanza]

What he said^^^^^^^^^

So are you going to share the codes or are they TOP secret?


Regards,
LarryB

 

[DucatiCraig]

I get one blink from the CEL light.

How do you interpret the flashes to the numeric codes?

 

[ralph cerbone]

I am not 100% sure, I never correlated the heater vs. 02 out of range codes. I know anytime I have a poor running NSX under part throttle if I disconnect the 02 sensors and it comes alive they are the problem. This is the case when there is no code. I force the code by disconnecting them. As I think further, since the scenario I describe here is based on no code at all, I think the heater open would cause it to disable the closed loop mode.

I will have to pose this question to Honda, Japan.

Regards,
LarryB

very intersting question by frank, my strengths are in GM diagnostics,in the early obd2 the heater was powered & gnd independent of the ECM,it didn'tknow if the heater was working, but our cars the ECM looks at the heater circuit (according to my 97 man.) OBD2 has monitors,continous & non continous, (misfire =continous, heaters =non continous), i would have to say if our cars lose the heater circuit the ECM will go to a learner mixture to protect the CAT, resulting in a stumble on accel. this is all based on program strategy ,the only way to know for sure is to cut the heater cir. while running and watch the injector pulse width , usually the ECM will go to a richer (safe ) ratio but i don't think so in this strategy .

 

[Daedalus]

As we're all just speculating... I don't see any reason for the ECU to go open loop for a bad heater circuit. A lot of O2 sensors don't have heaters. They all work just fine once they get hot enough; it just takes longer to get there without the heater. I know my Nissan will still go closed loop with a bad O2 heater.

 

[enkrypt3d]

Ive just had some header work done in the past few months... how do I know if the o2 sensors are plugged into the right spot? im not getting any codes and the car is running really weak... and its even weaker with the AC on... :frown: help!

 

[DucatiCraig]

Got the codes; I was in a hurry before and the paper clip wasn't seated correctly.

42 and 66, which would point to the 2 rear bank sensors being swapped, correct?


-

 

[ralph cerbone]

As we're all just speculating... I don't see any reason for the ECU to go open loop for a bad heater circuit. A lot of O2 sensors don't have heaters. They all work just fine once they get hot enough; it just takes longer to get there without the heater. I know my Nissan will still go closed loop with a bad O2 heater.

heaters were put in for 2 reasons, get to close loop (fuel control)faster &keep it in closed loop (sitting in traffic they would fall below threshold go to open loop, trust me on this one i've done the testing) the ECM wants about 160 degrees of water temp,600 degrees for the O2& 3 min timer(which has been shortened as systems progressed) .however
just because a heater fails does not mean open loop, but could change the program of the speed density system ,if the cars were going in open loop they would not be hesitating,they would be running rich,nice power ,from the complaint it sounds to me they are running somewhat lean,but again I'am just speculating

 

[DucatiCraig]

Still having the problem, depending on how I configure the plugs, I either get error code 42 or 42 AND 66.

Any thoughts??

Thanks,

- Craig

 

[Larry Bastanza]

At this point you need to troubleshoot it using the service manual procedures, and make sure they are connected correctly. Almost sounds like you have a bad 02 sensor AND you have a bad wire/connection.

Typically what happens is the connector pins can get pushed back in the connector body and not make contact. It you have a bad connection AND a bad 02 heater, what you are seeing would be the result.

HTH,
LarryB

 

[DucatiCraig]

At this point you need to troubleshoot it using the service manual procedures, and make sure they are connected correctly. Almost sounds like you have a bad 02 sensor AND you have a bad wire/connection.

Typically what happens is the connector pins can get pushed back in the connector body and not make contact. It you have a bad connection AND a bad 02 heater, what you are seeing would be the result.

HTH,
LarryB

Thanks for the reply. I'm inclined to think it's not a bad sensor, as the problem only appeared after the tranny swap. Now, a bad connection due to a pushed in pin, that makes sense. I'll check it out.

What I wish I had is a picture showing which connector plug each o2 sensor plugs into, but haven't found anything like that in the manual. That way I could verify that I have the correct o2 sensors plugged into the correct place on the harness. I don't think the service manual procedure is geared toward plugs in the wrong place, it seems its more for troubleshooting failed components that are plugged in correctly.

Ideas, or ??

Thanks again for the input.

 

[Larry Bastanza]

02 sensor connectors:

Rear Primary connects to rear valve cover
Front Primary connects to front valve cover(This 02 sensor is moved to the rear of the oil pan, by the header collector when you install headers)

Both Secondary 02 sensors are after the cats and plug in by the bracket attached to the rear passenger corner of the engine. The plugs are opposite sex, so you cannot mix them up.

HTH,
LarryB

 

[angus]

Were any of the sensors removed from the cats and put back in (possibly switched?) I had this problem before , car went crazy , swithched them back , and problems were gone!

 

[Larry Bastanza]

Were any of the sensors removed from the cats and put back in (possibly switched?) I had this problem before , car went crazy , swithched them back , and problems were gone!

mmm.....good point, and easily missed. You could stare at the secondaries all day and not realize it!!!!!!!!!!!!!

If anyone has a 1995+ car and can take a pic of this it would probably really help.

Regards,
LarryB

 

[DucatiCraig]

Angus -

Good point, but no, the sensors were not removed.


Larry -

That's exactly what I needed! I'll first verify that the sensors are plugged into the correct locations, then go looking for pins not making contact before I open the door to the coincidental simultaneous tranny swap / sensor failure possibility.

I'll let you know what I come up with.


- Craig

 

[ftuhy]

I can take pictures of my '96 secondary O2 sensors - what pics do you want? Just the connnectors for front and rear secondaries? I assume that's key since other pitcures of my OEM exhaust won't be of any use.

Let me know. (you can PM me as a reminder to check this posting)