VX on LPG 02 Sensor Question

[Skoti69]

In my v8 VX 2000 Commodore which is converted to LPG, I almost always have a check engine light on when driving on LPG. My OBD 2 gives me the code P152 - 02 Sensor 1 Bank 2 High Circuit Voltage. When viewing live data O2 sensor 1 Bank 1 will be running as normal, perhaps on the low voltage side and 02 1 Bank 2 will be running at above .9v constantly. When I switch to petrol, the values will pretty much swap and Bank 1 will run at a voltage about .8, and Bank 2 will run as normal or somewhat on the lean side. The check engine light eventually goes away and the code no long registers. I've tried putting in new o2 sensors, switching the o2 sensors from bank 1 to bank 2 and vice versa, but the same thing seems to happen. The car runs fine on both and it's not really an issue, just curious and wondering if anyone had any idea whatsup?

 

[strgas]

lean or rich running conidition can casue this reading high or low voltages . what type of gas system are you running .
any noticable exhaust leaks on bank 1 ?

 

[EYY]

Gasfitters have probably stuffed something up.

Is it a mixer system or is it injected lpg? Mixer systems tend to give worse mixtures and throughout the rev range.

 

[Skoti69]

Thanks for the responses! It's a Gastec system, mixer system I'm pretty sure uses a Fuel Processor with the number FP31. No noticeable leaks in either banks, I'll check again a bit later though. So you reckon might just need a tune? That's what I was hoping just thought it was strange that one bank would run rich but not the other.

When watching the live data through OBD 2 the Air/Fuel ratio is constantly at 14.6:1 which is what it should be I believe, but that's probably not a true reading as the LPG mixture would be processed by it's own separate computer, yes?

Wiring Diagram of LPG Processor attached.

 

[strgas]

cut the grey wire away from the o2 output and bridge the o2 wiring , leaving the brown wire only tapped onto the o2 output .

 

[Skoti69]

Thanks again for the reply! Could you please explain how this would work/fix the problem? I understand one of the wires is connected directly to o2 sensors and the other to the o2 sensor pcm wire, by removing the pcm one could I potentially change the block learn parametres, impacting on overall smoothness?

 

[EYY]

You need a wideband to see what's actually going on. Narrowband sensors won't be able to tell you what's really happening.

All he means is to remove the grey wire altogether. Currently, the o2 sensor signal runs into the lpg processor and then from the lpg processor to the factory ecu. So basically what he's telling you to do is reconnect the o2 sensor wire as per factory and tee into it with the brown wire.

They're still a crap system, the reason your CEL is on is because the ECU is trying to make changes to mixtures and it's not detecting the changes it should. Injected gas is the only way to go.

 

[Skoti69]

Sweet as I'll give it a go. I found the grey and brown wires and can trace them until they go under the radiator overflow tank which I guess i'll have to remove to continue tracing haha. Thanks for the help, open to other suggestions / opinions also Not really because it's causing any issues just got some free time and like it all to be working perfectly haha

 

[Skoti69]

Also might be worth mentioned that I just got the transmission swapped with a replacement unit could a wire have been cut accidentally or something?

The CEL comes on really indimiantely too, even though the sensor is always reading .9v or above. Could drive for a couple of hours without coming on sometimes, and sometimes will come on within 10 minutes.

 

[Skoti69]

So after cutting and bridging the wires got proper readings on both lpg and petrol for a few minutes, then both sensors started to run at .9v+ on lpg and they continue to do so. When I change to petrol i get normal readings from bank 1 but bank to reads 0.00 volts majority of the time, occasionally going up to 0.1 max. it is also driving very strange on petrol now and kinda surges at high speed..