Thread: Oxygen sensor issues / ecu to O2 wiring

whats wrong with 27 on gas?

how old is the MAF?

MAF reads 18 at idle and I've seen 270- 280 under load, which I assume is ok.
I have error codes for the O2 sensors and it's running very rich, when I had one O2 sensor working I had a reading of 0.85 whilst on gas, and .4-.6 on petrol for bank 2, I assume the gas system taps into bank 1, hence the rich O2 reading on bank 2 sensor.

The old O2 sensor from bank 1 was black, bank 2 was white/grey.

I might have to run a bypass wire to the ecu and test that.

Originally Posted by Mattblack59bus

MAF reads 18 at idle and I've seen 270- 280 under load, which I assume is ok.
I have error codes for the O2 sensors and it's running very rich, when I had one O2 sensor working I had a reading of 0.85 whilst on gas, and .4-.6 on petrol for bank 2, I assume the gas system taps into bank 1, hence the rich O2 reading on bank 2 sensor.

The old O2 sensor from bank 1 was black, bank 2 was white/grey.

I might have to run a bypass wire to the ecu and test that.

Firstly what brand of O2 sensor did you buy. Bosch are the genuine ones and are less likely to cause faults than the cheaper copies
Re over fueling it generally means a crook maf or a plug that isn't firing.
Have you pulled the plugs and see if they are wet or black also. could be a crook coil or lead.
When you disconnect the maf wiring whilst running does it do anything?
Cheers, Mario

I bought the last 2 O2 sensors in stock, unfortunately different brands, one Bosch and the other was NK something, I'm fairly certain I have a broken wire in the harness near the coil pack.
My Nanocom shows intermittent error codes for both O2 sensors now, originally it was just bank one which is shared between the LPG Gore Research fuel processor and obviously bank 1 when running on petrol, bank 2 was running normally on petrol.

It has to be O2 sensor related because LPG doesn't use the MAF sensor but it does use one O2 sensor.

I occasionally get valid O2 readings on the Nanocom, so has anyone had to rewire their O2 sensors to the ecu?

Cheers
Marc

If one of your sensors is NTK, I've not had any problems with that brand. As for the wiring, seeing where the connector plugs live I'd rather suspect that the contacts in the plugs are dirty. It's shocking hot down there and the plug seals may be roasted. Try some contact cleaner in them. I doubt that the wires have broken, but possibly the insulation is failing. The sensor output wires are coaxial from memory all the way to the ECU. I did strip down the loom in my wrecked V8 D2 for someone who bought the coil packs but I didn't keep the sensor wires. I imagine it wouldn't be too tough to get the relevant wires out of another loom and re-route them to your satisfaction. Wrecked D2 V8's are pretty common.

OK, I've cleaned every pin in the connectors using a fine rotating file (dremel part in a drill) and then cleaned it all out using MAF cleaner.
I've also verified continuity from the connector to further along the harness.

Now testing the O2 voltage with the car running (after warm up) results in a negative voltage -0.8V and had me thinking that the sensor was faulty and or possibly reverse wired, but I have two different brands of sensors with reverse voltages. Is it possible my ECU is starting to fail? or a bad ground?

Surely I can't be the first person to experience this issue?

Cheers
Marc

Originally Posted by Mattblack59bus

MAF reads 18 at idle and I've seen 270- 280 under load, which I assume is ok.

According to RAVE that's too low all the way cos you should get around 50 at idle and above 600 under heavy load, the V8 is well known to throw false fault codes from time to time as it has that "hybrid" OBD/OBDII protocol

If you're reading negative voltages from the sensors I suggest you go over each and every ECU/engine/chassis earth point cleaning and tightening as you go.