LukePerry085

I've had an issue that I've been chasing for a while now where my C5Z was running like complete crap. It took me a while to figure out the issue, but once I discovered that the Bank 1 O2 Sensor (this is the upstream sensor - I have no cats, therefore I have no downstream sensors either) was reporting an extremely rich condition I was able to bandaid the issue by unplugging the sensor. After doing that, the car ran beautifully, and by reading the plugs I can verify that my AFRs are quite alright.

Fast forward a few months and I now have EFI Live so I have much better insight into what the various systems are actually doing (I currently am driving the car in a Speed Density configuration, so the inputs from the o2 sensors are ignored completely). At idle the bank 2 sensor shows around 450mv most of the time, where the bank 1 sensor shows anywhere from 800-1000mv. I now have a wideband as well, and that also confirms my plug readings that show the AFR is good.

Obviously my first thought was that the o2 sensor is bad, so I went and bought 2 new ones and ended up with the same issue. Just for giggles I went ahead and plugged the bank 1 plug into the bank 2 sensor, and vice-a-versa. Same issue: The issue stayed with the Bank 1 computer channel!

Since the issue follows the Bank 1 o2 sensor channel I'm thinking that there has to be something wrong with my ECM. Any ideas?

2xLS1

iTrader: (25)

Speed Density by itself does not ignore O2 sensor inputs. If it is also in Open Loop, then that is what ignores them. You would have to be commanding Open Loop by settings in the tune or setting certain O2 sensor codes will force Open Loop. I would say that the B2S1 reading 450mv all the time is the real problem, not B1S1.

LukePerry085

Yes, I'm running in open loop.

Bank 2 is not reading 450mv all the time. I gave the average output at idle, which compares to the other reading 800 to 1000mv under the same conditions. The bank 2 sensor works normally under all conditions.

2xLS1

iTrader: (25)

What do you think normal O2 operation is in Open Loop? What are you expecting them to do? Why would you replace your O2 sensors if you are running in open loop.

LukePerry085

Let me clarify:

I am CURRENTLY running in open loop because of this issue. If I enable closed loop then it leans out Bank 1 due to the fact that the ECM believes it too be overly rich and the car runs like crap!

MontecarloDrag

iTrader: (3)

O2 sensor reading 450 mV all the time means a wiring problem, this is the same voltage you get when the sensor is unplugged.
You need to diagnose the sensor wiring and test for leaks to know if the sensor is the problem or the wiring or both.

LukePerry085

I misspoke and cleared that up in the 3rd post of this thread.

LSX Power Tuning

iTrader: (4)

Post a log.

Steve L.

Luke Perry, did you resolve this issue? I have been fighting a similar problem for two years with no resolution.