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I'm not the one doing the upgrade it was already done but it looks like it was done quickly & 1 of the wires is just hanging under the dash by the electrical connections on the driver side.a white wireAs stated, OBD1 uses a 1 wire sensor, though a heated 3 wire is a good upgrade.
Question is, what harness do you originally have? 1 wire or 3?
If you're the one upgrading, run the power wire to your fuel pump test port under the black cover, pass side firewall. The other wire should have an eyelet for a ground. At least that's how I upgraded my '95 2500 5.7's single wire that's located in the y-pipe, just upstream of the test pipe. I mean catalytic converter...
If it's not wired correctly, if you're unsure if it's working correctly, and if your engine programming is stock, my suggestion is to remove the 3 wire fiasco and install the OE designed 1 wire.I'm not the one doing the upgrade it was already done but it looks like it was done quickly & 1 of the wires is just hanging under the dash by the electrical connections on the driver side.a white wire
1 or 3 wire depends on year model and other equipment. Just saying OBD 1 uses the 1 wire sensor is incorrect. Many 94-95 model GMT400's use a 3 wire O2 sensor. Whether OP's does is in question; someone may have hacked his to 3 wire, or it started life as 3 wire but the wiring got damaged, as can happen. A visit to the factory service manual wiring diagram section for his specific year and equipment will tell the story plus help him determine how to repair the wiring.As stated, OBD1 uses a 1 wire sensor, though a heated 3 wire is a good upgrade.
Question is, what harness do you originally have? 1 wire or 3?
If you're the one upgrading, run the power wire to your fuel pump test port under the black cover, pass side firewall. The other wire should have an eyelet for a ground. At least that's how I upgraded my '95 2500 5.7's single wire that's located in the y-pipe, just upstream of the test pipe. I mean catalytic converter...
Many 94-95 model GMT400's use a 3 wire O2 sensor.
Richard
Almost every automatic transmission 1500 and 2500LD 1994-1995 I've owned/seen/worked on are 3-wire O2. I have owned a 1994 1500 with 1 wire O2 but it was an NV4500-optioned (rare) truck, and a 1995 with 1-wire but it was a 3500HD 7.4/NV4500.In my nearly 30 years of wrenching I've never seen a factory OBD1 GMT400 with a 3 wire O2 sensor. I'll take your word that they're out there, perhaps in Commiefornia, but I've never seen one.
And I have a Cali emissions equipped '95...
Thanks for the info Richard I'll look it up in the manual & see what it came with1 or 3 wire depends on year model and other equipment. Just saying OBD 1 uses the 1 wire sensor is incorrect. Many 94-95 model GMT400's use a 3 wire O2 sensor. Whether OP's does is in question; someone may have hacked his to 3 wire, or it started life as 3 wire but the wiring got damaged, as can happen. A visit to the factory service manual wiring diagram section for his specific year and equipment will tell the story plus help him determine how to repair the wiring.
Richard