Please help, 02 sensors will not read
10-31-2010, 06:53 PM
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Please help, 02 sensors will not read Put a 5.3 into a 39 Chevy and used a 2002 truck pcm. No mods at all; custom harness. O2's are reading 447-453 milivolt like its not plugged in.
Ohm tested the purple and tan wire from connector to pcm and tested good.
Volt tested the red and black wire and got 12.3 volts. No DTCs. I Reset the fuel trims and turned on fuel learn and they still arent reading. Ran an extra ground from battery to side of block to see if it helped. Put the PCM in a 2000 Chevy truck and the 02s will read. Put a complete different set of O2s in the car and it still will not read. All other sensors are reading.
I would appreciate any ideas at all.
Thanks.
Ohm tested the purple and tan wire from connector to pcm and tested good.
Volt tested the red and black wire and got 12.3 volts. No DTCs. I Reset the fuel trims and turned on fuel learn and they still arent reading. Ran an extra ground from battery to side of block to see if it helped. Put the PCM in a 2000 Chevy truck and the 02s will read. Put a complete different set of O2s in the car and it still will not read. All other sensors are reading.
I would appreciate any ideas at all.
Thanks.
10-31-2010, 07:09 PM
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Are you sure the custom harness is connected to Bank 1 Sensor 1 and Bank 2 Sensor 1 from the PCM? Not sure what pins they are - you would have to find a wiring diagram for the PCM... if they messed up and used Sensor 2 for both banks, it would do exactly what you are describing.
10-31-2010, 08:04 PM
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checked the pin outs and even changed them around; no difference.
I know it does make sence though. If the o2s are good and the pcm worked fine in another vehicle, then the harness has got to be it, but using the pin outs for a truck, or an f-body do not work.
I know it does make sence though. If the o2s are good and the pcm worked fine in another vehicle, then the harness has got to be it, but using the pin outs for a truck, or an f-body do not work.
11-01-2010, 02:16 PM
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For the 2002 year, there are 2 different configuration for O2 sensors: Isolated gorund and case grounded.
If you tested the PCM in another vehicle and worked good, then you have an electrical problem