Definition Chevrolet P1393
The Chevrolet P1393 code is an OBD-II diagnostic code that means “Crankshaft Position System Variation Not Learned”. This code primarily concerns General Motors (GM) vehicles, including Chevrolet models.
Possible Causes
- Crankshaft Position Sensor Variation Not Programmed – The PCM (Powertrain Control Module) has not recorded the sensor’s variation values.
- Problem with the Crankshaft Position Sensor (CKP) – Failure or malfunction.
- Wiring Issues – Damaged wires, loose connectors, or corrosion in the CKP sensor circuit.
- Mechanical Problems – Damage to the flywheel or reluctor ring (broken teeth or excessive wear).
- Problem with the PCM – Software or hardware failure of the control module.
Common Symptoms
- Engine Hard to Start or frequent stalling
- Unstable Idle
- Loss of Power or reduced performance
- Check Engine Light (MIL) illuminated
Diagnosis and Repair
- Check the CKP Sensor – Visually inspect and test its resistance.
- Inspect Wiring and Connectors – Look for cut wires, short circuits, or corrosion.
- Perform a Crankshaft Variation Learning Procedure (requires a GM/Chevrolet compatible diagnostic tool).
- Scan the PCM – Check for other fault codes and live data from the CKP sensor.
- Replace the CKP Sensor or Repair Wiring if necessary.
Important Note
Some Chevrolet models require a reset with a professional diagnostic tool (such as Tech2 or a compatible GM MDI tool) to properly record the crankshaft variation.
If the problem persists after these checks, it may be necessary to have the PCM inspected by a professional.