Troubleshooting Error Codes and CEL

[dyerhaus]

A while back, if I drove my 2001 996 Carrera rather spirited, two lights would illuminate on my dashboard: PSM Off and ABS. Many of you on this board recommended cleaning the MAF and replace it if cleaning didn’t help. So, I replaced the MAF and that fixed the problem. The car ran noticeably better (and I thought it ran great before that).

 

Now, I have a new (potentially related) problem. After I replaced the MAF, I cleared these codes:

    P0507 - Idle Control at Startup

    P1128 - Oxygen Sensing Adaptation, Idle Range, Bank 1

 

A couple of people suggested replacing the Fuel Pump Relay. I forget the reasoning, but it made sense. It’s also cheap (like $22) and easy, so I didn’t mind trying it. I had to order it though, the dealer was out. However, before it arrived, I took a weekend road trip (San Jose to LA, about six hours on the road). Half way there, the CEL illuminated. I had my OBD scanner with me, so I ran it and found these errors:

    P0507 - Idle Control at Startup

    P1128 - Oxygen Sensing Adaptation, Idle Range, Bank 1

    P1130 - Oxygen Sensing Adaptation, Idle Range, Bank 2

 

I cleared those errors as I really didn’t want to look at the CEL my entire trip. That helped, but two days later and half way home, the CEL came on again. Once I got home, I scanned the car again and got these errors:

    P0430 - Cat Conv. Efficiency, Bank 2

    P0420 - Cat Conv. Efficiency, Bank 1

    P1128 - Oxygen Sensing Adaptation, Idle Range, Bank 1

    P1130 - Oxygen Sensing Adaptation, Idle Range, Bank 2

 

I picked up the Fuel Pump Relay and replaced it, cleared the codes, and that’s currently where I’m at. Not sure if the CEL will come back on or not as I just replaced it and drove around the block afterwards.

 

The car has been running and driving just fine, no strange sounds, smells, and no rough idling either. The CEL came on at normal highway speeds (75ish), not during idling, slow speeds, or even performance driving. 

 

I’m wondering if anyone has any tips/advice what to do next if the Fuel Pump Relay doesn’t resolve the issue. Am I looking at Oxygen Sensors… or something else?

Edited May 9, 2017 by dyerhaus

[Schnell Gelb]

To diagnose, rather than keyboard-speculate we need Durametric/scanner info.

The easy ,first observation would be to watch a graph of the Pre and Post cat O2 sensors.They may show poor performance but this can be due to vacuum leaks. I mention this so you do not needlessly fit 4 new O2 sensors.