Since updating the motor several months ago have had a frustrating problem getting good O2 sensor data and closed loop. Need your recommendations. Detailed chronology is attached in second post below. The short version is the O2 wiring checked and several different sensors were tired without being able to get normal mV and crosscount response.

I next ran the troubleshooting procedure on SES Code 13 – O2 Sensor. FSM has you ground the O2 sensor and scan the mV and then has a decision point of 200 mV. Above 200 mV the FSM says indicates “faulty ECM connection or ECM” – for less than 200mV FSM says indicates bad sensor. Mine was 253mV. So I checked continuity on the sensor and ground leads from the ECM – they looked good - and then ordered a rebuilt ECM from Ecklers.

Want to make sure I am properly trouble shooting and not missing something else – are there any $6E closed loop parameters, wiring problems, or other gotchas I am missing? The ECM is 21 years old, was removed from the dash to hook up an emulation cable, and has been resting on the passenger floorboard for a while – It could certainly be the problem, and might explain why no sensor or wiring combination seemed to help.

 

Sep 2006 - Removed AIR system and installed Stainless Works headers, and installed a Caspers heated O2 sensor, with the heater circuit wired into a relay on the driver side fender. Got a BIN from Alvin for those changes and car ran fine. Wasn't data logging then but assume the O2 sensor worked OK and was going into closed loop, as I didn't get any SES lights.
Nov 2006 - Started data logging was using a $32 mask – that template didn't have a closed loop flag, and I didn't know enough to check it with diagnostic mode on the ALDL – so didn’t get any closed loop data points then.
June 2007 - Updated to new heads, camshaft, lifters, TB, big mouth manifold and runners, and injectors. Reinstalled the same O2 sensor - had some roughness and idle problems and it threw a code 13 and a code 45. Was running a BIN from Alvin made for the motor changes. Started more data logging with a $6E and saw that closed loop was intermittent and generally the fuel trim was rich.
July 2007 - Tried to get Alvin to update the BIN – and he requested Datamaster log files. Sent these and after reviewing them, he said there were problems with the O2 sensor. Researched this forum and 3rd Gen DIY PROM and got smarter on NB non linear response, mV ranges, and crosscounts. It was clear that the O2 sensor was lazy and / or erroneous.
August 2007 – Tried various attempts to fix the O2 sensor. Checked the voltages going to the senor – had 12v and gound to the heater circuit, and 170 mV going to the senor. Removed the units and the heater checked good manually. Replaced the O2 Sensor with another a Denso unit, with no improvements, then replaced the sensor and wiring completely with another new Casper’s unit – none of these changes brought a consistent O2 sensor capability.
August 2007 - Then had the car dyno tuned with a wide band sensor – base fuel trim was adjusted and runs well, and we locked out the closed loop by setting a closed loop temp constraint to 300F. Next Tried a GM 3 wire O2 sensor, 25312179 aka AFS-74, and wired it up – reviewed the mV in the data log and could not get regular response to engine / throttle movements. Starts at 451mV and then after a minute or so goes to 253mV or so and stays there.
August 2007 – Troubleshot according to the SES Code 13 procedures in the FSM. The procedure has you confirm open loop and then ground the O2 sensor terminal scan the O2 mV. If less than 200 mV it directs “faulty oxygen sonser connector or sensor”, if 200mV or above it indicates “Check for open oxygen sensor signal CKT 412 or 413. If CKT 412 or 413 OK, it is faulty ECM connection or ECM” . Mine was reading 253mV. Saw ground continuity at D6 from the ECM (sensor signal ground), and good continuity through D7 (sensor signal) . We had pulled the motor for the engine work so I thought maybe there was some wiring issue – wasn’t sure where this D6 engine ground connects on the engine. I looked in the FSM for the ground and saw that it (tan wire CKT413 ) it joins a wire (brown CKT486) from the ESC module but couldn’t verify these on the engine. Ordered new ECM.

 

I cant read most of that ubove, the text is just too small.

Where is this O2 sensor located? Can you get a picture of the headers?

Id consider the fact its probably too far away and cooling off too much to operate properly.

 

Case, - text is normal size now. The O2 sensor is just past the collector and is heating the sensor.

 

No worries, ill be back in a few minutes mate, ill read up and see what i can see

 

I had this issue recently with my 94, although it wasnt bad enough to set a code.

My headers are of the Tri-Y design:




I had the O2s at the final collectors on each side, and no matter what i did, i couldnt stop the left from occationally dropping out at idle. 94s have heated O2s as standard. I replaced both sensors and had no changes, so i swaped the sensors from left to right and had no changes either. Its not the first time ive heard of it happening even with heated sensors.

Youll see in the 3rd pic there is a place to put the O2 sensor after the primary collector on the 3 and 5 tubes. While i understand your headers are probably 4 into 1 instead of Tri-Y, i reckon you could still get away with this by having the O2 fitted to read from either 5 or 7, which will allow you to get the sensor alot closer to the heads.

Ive seen pictures of 4 into 1 long tubes that had a location for the O2 sensor in the number 7 tube, and as long as nothing goes wrong with number 7, the reading should still be good enough to do the job.

I cant garrentee this will fix the issue so im going to leave that choice completely up to you whether or not you give it a go, but i certainly reckon its worth a try. I dont think it would cost alot to try it, and if it does fix it youre laughin

 

Thanks for the pics and ideas case. Seems almost everyone else can get their O2 sensor working at collector join - can see why yours may be a problem with the tri y construction. I get the new ECM in a day - if that doesn't work I am back to square 1.

 

Hopefully that will fix it for you mate yeah, but if not, you may as well give my sugestion a try.

I did have mine at the final collector as i said, and the design didnt make any difference there, being Tri-Y or 4 into 1 it was still reading all 4 on each side. 3 perfectly good heated O2s did the same thing in that left hand header.

Are your headers ceramic coated or any other type of coating that may cool the exhaust gasses? Mine are coated inside and out, and if you look in the pics you can sort of see where the gasses have been cooled off not long after the primary collectors.

 

[OT]Is that a V35?[/OT]

 

Update - O2 Closed Loop RESOLVED
Replaced the ECM with a rebuilt from Eckler's and the O2 crosscounts went into what appears to be a normal rythm. I reset the Closed Loop Temp enable (we had used that constant to lock out closed loop), and car went into Closed loop and stayed there. Yahoo!

Appreciate anyone with Datamaster reviewing the file to confirm O2 Closed Loop operation (and any other suggestions). Also what are good parameters for the three Closed Loop enable timers and temps. Thanks!!
DataMaster Log File Link for Review

 

Looks good to me
As for timers, if you have a heated O2, you can shorten them. I think I set my 60, 45, 30 (seconds). Then it's up to the rest to decide when closed loop kicks in.