O2 Blues

Have a real frustrating situation. Getting CEL with O2 codes. I have recently replaced both O2 sensors pre-cat. with Bosch units. Was getting codes previously for heater ckt. on those sensors.

I am now getting the following codes:

P0131
P0151
P0157
P0137

All low voltage generic codes. The P0131 is the one that triggered the CEL. The other 3 are pending codes.
All 4 sensors going at the same time is suspicious to say the least. Especially since the 2 pre cat ones are new.
The car runs just fine. I guess this is not surprising since the car would be running in "open loop" and making estimates
for fuel/air requirements.
I have reset the codes but they come back within 5 -10 miles of driving.
Did the usual, cleaned the contacts, applied stabilant, etc. No luck

I have a few theories, but thought someone here might have a few thoughts on this.

FYI - Only modification on this car is a Tubi exhaust. Everything else stock.

Oh yeah, I also did the OBD2 pin 4 update. Ferrari would not do it to my car or give me the parts because according to them, based on the VIN number it was not needed. Probably since the car was originally sold in Dubai and imported to US later. If anyone needs an OBD pin socket to do the update themselves, send me a PM and I'll send you one for free. Bought 10 of them to make it worth while.

Steve

 

Tom,

Actually I have been following your thread. Right now it is just frustrating as the car runs fine, just an annoying CEL that keeps popping up. Unfortunately Minnesota is not the Ferrari Mecca California is, making diagnosis difficult to say the least. Seems strange the ECU swap in your car only remedied one side of O2 sensors. Sounds like more that 1 problem. Unfortunately, my OBD reader doesn't give live data. Probably will invest in laptop program that gives live data.

Steve

 

Well thanks to Eric355, Loser and 355Spider for all the input Also to KJB355.

I also purchased the ElmScan Bluetoth and Scan XL like Loser is using. Definitely a very useful diagnostic tool.
KJB355 put me in touch with a Bosch technician who sent me a detailed Motronic 5.2 schematic for tracing the system. My first thought and the thought of the Bosch tech was that I had a grounding issue (lack of) somewhere in the system. Attaching a ground to the O2 sensor housing appeared to help at first but threw codes again.
P0131 - triggered CEL
P0151 and P0153 pending
Eric was kind enough to explain what I should be looking for in O2 signal output and suggested how to view the parameters with my software.

Totally frustrated I decided to step back and look at it from when I first started having problems.

Got a CEL that we traced to O2 sensor B1S1 no voltage. Purchased a Universal Bosch sensor and replaced it. Kept getting DTCs off and on causing me to replace the B2S1 sensor also. This one I replaced with a OEM style with connector. At this point is where I posted the original thread with all of the DTC codes.

After reading Losers thread and doing some research on my own, I decided to look at everything I had done so far. Specifically I was concerned about the erroneous information concerning the proper O2 sensors for my car (96 GTS) I had read about. As it turns out, I was able to determine 2 things.

1) The first sensor I replaced was wrong. I used a Universal Post Cat sensor in the pre-Cat position. Duh!!!

2) Using the diagnostic software with input from Eric he suggested to check the voltage of all 4 sensors with the key on only (not running). He said voltage should read around 0.43 volts. Low and Behold 3 of 4 sensors were at approx 0.45 volts and the 4th sensor, you guessed it, B1S1 "Zero Volts".


Sooooooooooooooooo...........................

3) Purchased another O2 sensor (made sure to get the right one, Universal Bosch pre-cat sensor). Removed the old one and connected up the new one. Viola! 0.45 volts all 4 sensors.

4) Cleared all my codes. All 4 sensors now appear to be responding.

So far 4 drive cycles, system runs in closed loop. No DTCs pending or otherwise! Yahoo!

We'll see where it goes from here.

Moral of the story? Make sure you use the CORRECT PARTS!

 

Thanks again for the help. Still some unanswered questions though.
1) Did the Post cat sensor in the Pre Cat location go bad or is there something that causes it to go to Zero volts in the wrong position? I'll send an e-mail to the Bosch tech to get his input on that one.

2) Was this a contributor to pending O2 codes on the other sensors?

3) I did have a P0102 MAF low voltage code but that seemed to be cleared up by using contact cleaner and MAF cleaner so I am assuming unrelated (separate issue).

I'm a believer that when you get erratic results, as in this case, several different codes, there may be more than one issue.

Eric, contrary to your suggestion, at least as far as the universal sensors go, the tip configuration is identical. I'll post some photos later. Also the tip configuration is very different from the "OEM style".

I'm wondering if there are some bench tests that can be done on an O2 sensor to determine if it is working "in spec"? Another question for the Bosch tech.

I'll "rev her up this weekend" and get some MAF readings and let you know Eric.

285 - THANKS AGAIN FOR THE REFERENCE ON THE CONNECTOR!