What are the common causes of P066B?

A short to voltage on the cylinder 1 glow plug wire. A failed cylinder 1 glow plug. Corrosion at the cylinder 1 glow plug connector. A failed glow plug control module. A faulty ECM command to the module.

Check the cylinder 1 glow plug resistance. Inspect the cylinder 1 glow plug wire for a short to voltage. Inspect the glow plug connector for corrosion. Test the glow plug control module output. Replace the glow plug or module if the fault stays. Clear the code and retest.

P066B

Cylinder 1 Glow Plug Control Circuit High

System: Computer output circuits (P code)
Lamp: Check Engine Light
Category: Powertrain - Computer and Auxiliary Controls

What it means

P066B means Cylinder 1 Glow Plug Control Circuit High.

Check these first

A short to voltage on the cylinder 1 glow plug wire
A failed cylinder 1 glow plug
Corrosion at the cylinder 1 glow plug connector
A failed glow plug control module
A faulty ECM command to the module

What to do next

Check the cylinder 1 glow plug resistance
Inspect the cylinder 1 glow plug wire for a short to voltage
Inspect the glow plug connector for corrosion
Test the glow plug control module output
Replace the glow plug or module if the fault stays
Clear the code and retest

Look up another code

Code or symptom

Enter a full code or a symptom. Press / to search. How to read a code

Type a code above, or start from a symptom or a common code.

Updated

Generic SAE J2012 definition. Last updated 2026-10-10.