What causes GM code 18?

Open or shorted crank reference signal wire between the distributor and the ECM Failed distributor pickup coil or ignition control module Loose or corroded connector in the reference circuit On 5.7L VIN P engines a shorted injector circuit can also set this code

How do I fix GM code 18?

Retrieve codes with a paperclip across ALDL pins A and B and count the Check Engine flashes Check the crank reference signal at the ECM while cranking Inspect the distributor pickup coil and ignition module wiring On a 5.7L VIN P engine test the injector circuits for a short Clear codes after the repair and recheck after a road test

18 Crank Signal Circuit Fault

Q: What does GM code 18 mean?

GM code 18. Crank Signal Circuit Fault. Applies to 1982-1995 GM cars and C/K trucks, Camaro, Corvette.

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

How to read it

Code 18 reads as 1 flash, pause, 8 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 18 mean?

18. Crank Signal Circuit Fault. This code sets when your vehicle computer detects crank signal circuit fault.

Common causes of 18

Open or shorted crank reference signal wire between the distributor and the ECM
Failed distributor pickup coil or ignition control module
Loose or corroded connector in the reference circuit
On 5.7L VIN P engines a shorted injector circuit can also set this code

How to fix 18

Retrieve codes with a paperclip across ALDL pins A and B and count the Check Engine flashes
Check the crank reference signal at the ECM while cranking
Inspect the distributor pickup coil and ignition module wiring
On a 5.7L VIN P engine test the injector circuits for a short
Clear codes after the repair and recheck after a road test