What causes GM code 34?

MAP sensor signal wire shorted to ground Failed MAP sensor with low output Blocked or kinked vacuum hose on some models Faulty ECM reference voltage on rare cases

How do I fix GM code 34?

Read MAP voltage through the ALDL port and confirm it stays low Inspect the signal wire for chafing to ground Apply known vacuum with a hand pump and watch sensor response Test reference voltage and ground at the sensor connector Replace the sensor only after wiring tests good

34 MAP Sensor Circuit Error Signal Low

Q: What does GM code 34 mean?

GM code 34. MAP Sensor Circuit Error Signal Low. Applies to 1982-1995 GM cars and C/K trucks, Camaro, Corvette.

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

How to read it

Code 34 reads as 3 flashes, pause, 4 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 34 mean?

34. MAP Sensor Circuit Error Signal Low. This code sets when your vehicle computer detects map sensor circuit error signal low.

Common causes of 34

MAP sensor signal wire shorted to ground
Failed MAP sensor with low output
Blocked or kinked vacuum hose on some models
Faulty ECM reference voltage on rare cases

How to fix 34

Read MAP voltage through the ALDL port and confirm it stays low
Inspect the signal wire for chafing to ground
Apply known vacuum with a hand pump and watch sensor response
Test reference voltage and ground at the sensor connector
Replace the sensor only after wiring tests good