GM P1639 Error Code: How to Fix It

Q: What causes GM P1639 error code?

P1639 is caused by problems with the 5V reference circuit 2, including shorted sensors, damaged wiring, poor connections, or a faulty ECM. Water damage and corrosion are also common causes.

Q: Can I drive with P1639 code?

You should not drive with P1639 as it affects critical engine sensors. The vehicle may experience poor performance, stalling, or may not start. This is a high-severity code requiring immediate attention.

Q: How much does it cost to fix P1639?

Repair costs range from $50-100 for sensor replacement to $800-1500 for ECM replacement and programming. Wiring repairs typically cost $150-400 depending on extent of damage.

Q: Which sensors use the 5V reference circuit 2?

Common sensors include throttle position sensor (TPS), mass airflow sensor (MAF), manifold absolute pressure (MAP) sensor, and accelerator pedal position sensor, though this varies by GM model year.

Q: Will P1639 cause my GM vehicle to fail emissions testing?

Yes, P1639 will cause an emissions test failure as it indicates a malfunction in the engine management system. The code must be repaired and the readiness monitors must complete before passing emissions testing.

Abstract

GM error code P1639 indicates a malfunction in the 5V reference circuit 2, which provides power to critical engine sensors. This high-severity code can cause poor engine performance, stalling, or prevent the vehicle from starting properly.