1991 GMC C2500 OBD1 code 85 - prom error

Tiny
RAY_CARSON
  • MEMBER
  • 1991 GMC C2500
  • 5.7L
  • V8
  • 2WD
  • AUTOMATIC
  • 200,000 MILES
I have no clue what the code 85 - prom error means, the truck has an intermittent misfire, it rev's up at times and stalls at others, I have replaced the ignition control module, in the distributor, and it seems to have fixed about half of my problems, but the truck still is not right, is there anything you can do to help shed some light on what else the, 85-prom error, means needs to be replaced? I have entered into a realm beyond my knowledge, so any help is greatly appreciated. Thanks Ray
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Thursday, November 19th, 2015 AT 10:07 AM

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Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Code 85 is a trans problem but if engine misses fix that first. It may be a vacuum leak under tbi unit as they blow gaskets there. On output sensor if it reads ok then it's either a short in system a bad cluster or bad connections
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Friday, November 20th, 2015 AT 7:59 AM

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