"sensor fault" but no DTC!?!

**PON-TON** · 03-28-2011, 06:20 AM

Quick question. Reading my data with two different scanning programs I get under fuel status:"closed loop" "sensor fault" on my bank 2. I have no DTCs and the oxygen sensor voltage readings seem very close to Bank 1. I can't find any online info on this situation and would appreciate any help. Thanks!

**pajeff02** · 03-28-2011, 08:31 AM

Not sure on this one. Could be as simple as a blown heater circuit. Once the sensor is heated by the hot exhaust gases it may appear to read fine on the scanner. If you are watching the output in mV it shoud be very rapidly cycling up and down.

**PON-TON** · 03-28-2011, 08:45 AM

I'll try to observe that when I can, but it's output closely matches the Bank 1 sensor at all times. Both o2 sensors are brand new.

**pajeff02** · 03-28-2011, 08:50 AM

You can swap the sensors left to right and see if the fault follows it.

**PON-TON** · 03-28-2011, 08:54 AM

well that's a pretty good suggestion! I'll get the beast airborne tonight and swap 'em. Thanks!

**pajeff02** · 03-28-2011, 12:03 PM

If the sensors have 75,000 or more miles on them, it's not a bad idea to change them out. Over time, their performance degrades and can impact your fueling.

**PON-TON** · 03-28-2011, 12:09 PM

well that is why I am a bit hacked, I just replaced them before this happened. I inspected the connectors and wires back to the main harness and all looked "tip-top" with no visible header burns. I'll try swapping them and that should tell me if its sensor or harness.
Fun.

**PON-TON** · 03-28-2011, 06:54 PM

The DTC finally popped up driving home from work, 0160 (bank 2 sensor 2) so evidently my o2 simm is funky. Good time to learn to delete those codes for good. Thanks for the info!

**pajeff02** · 03-29-2011, 03:04 AM

The rear sensors simply tell the PCM if the cats are working -- no affect on how your car runs or its fueling. Good to hear that you got it figured out.