C4 Corvette How-To: Determine Engine Trouble Codes (1985-1991)

DISCLAIMER The information contained within the How-To section of this site are submitted by members. Vette Registry is not responsible for the content and does warranty nor can be held liable for the information within.

To see which trouble code or codes are being set in your ECM is to jumper the A and B pins of the 12 pin ALDL OBD1 connector with a paper clip.
While the car is off, sitting still, turn the ignition key forward while this jumper is in place. Do not start the car. The Service Engine Soon ( SES ) light will flash in a repeating sequence, telling which trouble codes have been set in the ECM.
--------------------------------------------------------------------------------

1985 to 1991 Engine Codes

Code #12: Normal No Codes.
Code #13: Open Oxygen Sensor Circuit.
Code #14: Coolant Sensor Circuit Low.
Code #15: Coolant Sensor Circuit High.

🔒 Want to Read More?

This complete reference guide includes all engine trouble codes for 1985-1991 C4 Corvettes:

✓ Complete code list (12-62)
✓ Detailed descriptions for each code
✓ Sensor and system diagnostics
✓ ALDL connector procedure
✓ SES light flash patterns

Join Vette Registry to access the full article plus thousands of other how-tos, tech discussions, and registry features!

Join Now - It's Free! Already a Member? Sign In