I've been having persistent issues with downstream O2 sensor heater circuit voltage issues (high and low) on both sides. Codes P0031, P0037, P0051, P0057.
With a lot of help from a forum member @lowflyer001 who patiently answered my questions and pointed me in the right direction, I think I've sorted the issue.
The root cause of the problem was that when my PO put a reman motor in the Jeep about 25k miles ago, the mechanic didn't ground the O2 sensor circuit to the body in the usual spot (behind the passenger side heat shield), instead they grounded it to a stud on the motor right by the knock sensor.
I did two things to fix it, I replaced the ground from the battery to the body, the old one was a bit dodgy, I then added a ground from the stud on the motor where the harness is grounded to the body behind the heat shield. I used pre-made starter motor ground cables (because they had really well made connections properly integrated into the heavy duty cables. The 19" starter grounds were only $6 each. Of course, over the last 9 months of tracking this issue down I've spent a couple of hundred $$ on new (unnecessary) O2 sensors, heat shields, and sundry other attempts.
Since doing this work all the I/M readiness checks have completed and there are no stored or pending codes. I really think this i the solution.
Huge thanks to lowflyer001 for all the help. This forum is awesome.
Ian
With a lot of help from a forum member @lowflyer001 who patiently answered my questions and pointed me in the right direction, I think I've sorted the issue.
The root cause of the problem was that when my PO put a reman motor in the Jeep about 25k miles ago, the mechanic didn't ground the O2 sensor circuit to the body in the usual spot (behind the passenger side heat shield), instead they grounded it to a stud on the motor right by the knock sensor.
I did two things to fix it, I replaced the ground from the battery to the body, the old one was a bit dodgy, I then added a ground from the stud on the motor where the harness is grounded to the body behind the heat shield. I used pre-made starter motor ground cables (because they had really well made connections properly integrated into the heavy duty cables. The 19" starter grounds were only $6 each. Of course, over the last 9 months of tracking this issue down I've spent a couple of hundred $$ on new (unnecessary) O2 sensors, heat shields, and sundry other attempts.
Since doing this work all the I/M readiness checks have completed and there are no stored or pending codes. I really think this i the solution.
Huge thanks to lowflyer001 for all the help. This forum is awesome.
Ian
