OBD-I Codes List

GM 85 PROM Error

Make
GM (1982-1995)
Category
Powertrain - Computer and Auxiliary Controls
Severity
Check Engine Light

How to read it

Code 85 reads as 8 flashes, pause, 5 flashes on the check-engine light. Jump terminals A and B on the ALDL connector with the key off, then turn the key on with the engine off and count the check-engine flashes.

New to flash codes? The How to Read GM OBD-I Codes with a Paperclip walks through the test and what the numbers mean. The general OBD-I guide covers the rest.

What does GM code 85 mean?

PROM Error

Common causes of 85

  • Loose or corroded PROM or MEMCAL in the ECM
  • Wrong PROM for the vehicle
  • Failed PROM chip
  • Poor ECM connector contact

How to fix 85

  1. Read codes with a paperclip jumper
  2. Remove ECM power, reseat the PROM or MEMCAL carefully
  3. Inspect PROM pins and socket for corrosion
  4. Verify the PROM matches the vehicle calibration
  5. Replace with the correct PROM if the error persists
  6. Do not drive far with this code since fueling may be wrong

Source

Qualified source review

Sources and review

Review: qualified. Read the source limits below.

  • GM and Chevrolet OBD1 Trouble Codes (ALDL Fault Code List)

    live reference page (troublecodes.net)

    Supports: code identity and GM meaning

    Fetched directly. Single publisher, so the record is qualified, not verified. Causes and check order are curator-written from the circuit the code names.

    https://www.troublecodes.net/gm/

Last updated 2026-09-19.

Report a correction for 85. Include your vehicle, the issue and a source if you have one.

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