LT1-LT4 Modifications 1993-97 Gen II Small Block V8

where are the o2 grounds?

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Old 05-08-2013, 06:58 PM
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Default where are the o2 grounds?

specifically the front o2 sensors.
Old 05-08-2013, 08:24 PM
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They ground through the PCM, and all the PCM grounds I can think of are on ends of the cylinder heads.
Old 05-08-2013, 09:30 PM
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thank you ed wright.

my car is having an issue where it stumbles, backfires, and/or dies under heavy acceleration and wot. the only codes i have are 0133 and 0153 for o2 slow response on both banks. i have long tube headers so i thought these codes were normal with lt headers. i replaced both front o2s recently, cleaned my maf, checked the o2 wires and no change. i dont think its fuel related because the car primes, starts right up, and drives fine under normal acceleration. i plan on doing a plug change this weekend but i doubt that will help much since im not getting missfire codes. the more i research this site for similar problems im having, im thinking it may be a result of the tune i recently got from madtuner (i had him tune out the rear o2s and egr so maybe somehow the front o2s were affected by mistake?). the car ran great for about 50 miles after i got my pcm back from him. im lost in all the "it could be this or that". im thinking about just taking it somewhere for a dyno tune instead of throwing parts at it.

i know you have tuning experience and i've read that you are mr. lt1, what do you think ed?
Old 05-08-2013, 09:40 PM
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BB -

My 96 GM Service Manual says the BLK (i.e. - GND) wire on all 4 of the O2 sensors' heating elements ground at the ground point on the front of the Driver's side cylinder head, adjacent to the Ignition coil and IC Module.

The PNK (i.e. - B+) wire is HOT in Run and Start, while the TAN and PPL (or Tan / WHT and PPL / WHT) wires are the actual signal and return wires for the sensor portion of the O2 sensors, and (as Ed said), these wires only go to the PCM.

I hope this helps!

: )
Old 05-09-2013, 07:57 AM
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BB, the PCM can't change, therefore it isn't the tuning. Something happened to the car. It won't be the O2s causing that problem. More likely ignition would be my guess.
Old 05-09-2013, 04:29 PM
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Originally Posted by great421
BB -

My 96 GM Service Manual says the BLK (i.e. - GND) wire on all 4 of the O2 sensors' heating elements ground at the ground point on the front of the Driver's side cylinder head, adjacent to the Ignition coil and IC Module.

The PNK (i.e. - B+) wire is HOT in Run and Start, while the TAN and PPL (or Tan / WHT and PPL / WHT) wires are the actual signal and return wires for the sensor portion of the O2 sensors, and (as Ed said), these wires only go to the PCM.

I hope this helps!

: )
thanks for the info. good to know even if it doesnt solve my issue.

Originally Posted by Ed Wright
BB, the PCM can't change, therefore it isn't the tuning. Something happened to the car. It won't be the O2s causing that problem. More likely ignition would be my guess.
ok thats somewhat of a relief to hear. i rented a fuel pressure test kit today just to be sure its not fuel related and i'll be changing plugs and inspecting plug wires this weekend.



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