What causes GM code 86?

Internal ECM fault Low system voltage confusing the ECM Poor ECM ground Water intrusion in the ECM

How do I fix GM code 86?

Read codes with a paperclip jumper Check battery voltage and charging output Clean and tighten ECM grounds Inspect the ECM for moisture or corrosion Clear the code and retest with a charged battery Replace the ECM if code 86 returns with good power and grounds

86 ECM Analog To Digital Conversion Error

Q: What does GM code 86 mean?

GM code 86 — ECM Analog To Digital Conversion Error. Applies to 1988-1995 C/K trucks, Camaro, Corvette, Caprice.

Make: GM (1982-1995)
Category: Powertrain - Computer and Auxiliary Controls
Severity: Check Engine Light
Applies to: 1988-1995 C/K trucks, Camaro, Corvette, Caprice

How to read it

Code 86 reads as 8 flashes, pause, 6 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.

What does GM code 86 mean?

86 — ECM Analog To Digital Conversion Error. This code sets when your vehicle computer detects ecm analog to digital conversion error.

Common causes of 86

Internal ECM fault
Low system voltage confusing the ECM
Poor ECM ground
Water intrusion in the ECM

How to fix 86

Read codes with a paperclip jumper
Check battery voltage and charging output
Clean and tighten ECM grounds
Inspect the ECM for moisture or corrosion
Clear the code and retest with a charged battery
Replace the ECM if code 86 returns with good power and grounds