What causes GM code 77?

Failed EGR solenoid winding Stuck EGR pintle from carbon Chafed wiring near the exhaust Faulty ECM EGR driver

How do I fix GM code 77?

Read codes with a paperclip jumper Test solenoid 3 resistance and compare with the other two Inspect wiring routed near hot exhaust parts Verify ECM command reaches the valve Clean or replace the valve as tests show Clear the code and drive to confirm it stays off

77 Digital EGR Solenoid 3 Circuit Error

Q: What does GM code 77 mean?

GM code 77. Digital EGR Solenoid 3 Circuit Error. Applies to 1988-1995 Cavalier, Corsica, Beretta, C/K trucks with digital EGR.

Make: GM (1982-1995)
Category: Powertrain - Auxiliary Emissions Controls
Severity: Check Engine Light
Applies to: 1988-1995 Cavalier, Corsica, Beretta, C/K trucks with digital EGR

How to read it

Code 77 reads as 7 flashes, pause, 7 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 77 mean?

77. Digital EGR Solenoid 3 Circuit Error. This code sets when your vehicle computer detects digital egr solenoid 3 circuit error.

Common causes of 77

Failed EGR solenoid winding
Stuck EGR pintle from carbon
Chafed wiring near the exhaust
Faulty ECM EGR driver

How to fix 77

Read codes with a paperclip jumper
Test solenoid 3 resistance and compare with the other two
Inspect wiring routed near hot exhaust parts
Verify ECM command reaches the valve
Clean or replace the valve as tests show
Clear the code and drive to confirm it stays off