wiring harness ??? and o2 sensors

busta9876 · 10-17-2009, 02:04 AM

Working on a wiring harness, appears to be a 2002, as NO EGR, and RED/BLUE pcm, pcm says GMC Truck 4.8L. Vin shows it was USA built.

The Bank 1 Sensor 1 has flat 4 pin, which is the CASE GROUNDED sensor
The Bank 2 Sensor 1 has square 4 pin, which is ISOLATED GROUND sensors.

Both REAR o2's are the ISOLATED GROUND sensors with square plug. Anyone run into this before with one case and one isolated ground o2 sensor in same harness?

GM shows both schematics in service information, but not One of each mixed together.

gofastwclass · 10-17-2009, 10:46 PM

Quote:

Originally Posted by busta9876

Working on a wiring harness, appears to be a 2002, as NO EGR, and RED/BLUE pcm, pcm says GMC Truck 4.8L. Vin shows it was USA built.

The Bank 1 Sensor 1 has flat 4 pin, which is the CASE GROUNDED sensor
The Bank 2 Sensor 1 has square 4 pin, which is ISOLATED GROUND sensors.

Both REAR o2's are the ISOLATED GROUND sensors with square plug. Anyone run into this before with one case and one isolated ground o2 sensor in same harness?

GM shows both schematics in service information, but not One of each mixed together.

Weird, I thought all USA built trucks had the flat connector and the square was for Canada trucks. Has it been spliced?

busta9876 · 10-18-2009, 01:15 AM

no evidence of splicing. Since the harness is wired as a isolated ground o2 sensor circuit, I am going to remove the flat connector, and replace it with the white square one, that way can run same part# on both sides. The harness has all 4 o2 sensor TAN wires going to a splice pack, then 5 wires to the PCM Blue pin 25,26,28,29,63.

I would guess in the 2003+ PCM's the pin 25,26,28,29 get the Ground reference inside the PCM, and the pin 63 which is a GROUND REFERENCE is no longer required.