What causes GM code 31?

Misadjusted park neutral position switch Corroded PRNDL switch contacts Damaged wiring between the switch and ECM On turbo models a wastegate solenoid fault uses this same code

How do I fix GM code 31?

Verify the engine cranks only in park and neutral Inspect and adjust the position switch per the service manual Test switch continuity in each gear position Clean or replace corroded connectors before replacing the switch On turbo 3.8L models test the wastegate solenoid as the alternate cause

31 Gear Position Switch Circuit Error

Q: What does GM code 31 mean?

GM code 31. Gear Position Switch Circuit Error. Applies to 1988-1995 GM cars and C/K trucks with automatic transmission.

Make: GM (1982-1995)
Category: Powertrain - Transmission
Severity: Check Engine Light
Applies to: 1988-1995 GM cars and C/K trucks with automatic transmission

How to read it

Code 31 reads as 3 flashes, pause, 1 flash 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 31 mean?

31. Gear Position Switch Circuit Error. This code sets when your vehicle computer detects gear position switch circuit error.

Common causes of 31

Misadjusted park neutral position switch
Corroded PRNDL switch contacts
Damaged wiring between the switch and ECM
On turbo models a wastegate solenoid fault uses this same code

How to fix 31

Verify the engine cranks only in park and neutral
Inspect and adjust the position switch per the service manual
Test switch continuity in each gear position
Clean or replace corroded connectors before replacing the switch
On turbo 3.8L models test the wastegate solenoid as the alternate cause