What causes GM code 59?

Open trans fluid temp sensor circuit Unplugged trans case connector Broken wire in the internal trans harness Failed temp sensor

How do I fix GM code 59?

Read codes with a paperclip jumper or an ALDL scan tool Inspect the external trans connector for pins pushed out or corrosion Test continuity from the ECM to the trans connector Measure sensor resistance and replace if open Repair the harness, reconnect and clear codes Confirm the temp reading moves as the trans warms up

59 Trans Fluid Temp Sensor Circuit High Voltage

Q: What does GM code 59 mean?

GM code 59 — Trans Fluid Temp Sensor Circuit High Voltage. Applies to 1991-1995 C/K trucks, Suburban, Caprice, Roadmaster.

Make: GM (1982-1995)
Category: Powertrain - Transmission
Severity: Check Engine Light
Applies to: 1991-1995 C/K trucks, Suburban, Caprice, Roadmaster

How to read it

Code 59 reads as 5 flashes, pause, 9 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 59 mean?

59 — Trans Fluid Temp Sensor Circuit High Voltage. This code sets when your vehicle computer detects trans fluid temp sensor circuit high voltage.

Common causes of 59

Open trans fluid temp sensor circuit
Unplugged trans case connector
Broken wire in the internal trans harness
Failed temp sensor

How to fix 59

Read codes with a paperclip jumper or an ALDL scan tool
Inspect the external trans connector for pins pushed out or corrosion
Test continuity from the ECM to the trans connector
Measure sensor resistance and replace if open
Repair the harness, reconnect and clear codes
Confirm the temp reading moves as the trans warms up