What are the common causes of P066C?

A shorted cylinder 2 glow plug pulling the circuit low. A blown fuse in the glow plug control circuit. Corrosion or damage in the cylinder 2 glow plug wiring. A grounding fault in the glow plug harness. A failed glow plug control module.

Check the glow plug circuit fuse and replace if blown. Test cylinder 2 glow plug resistance against the other cylinders. Inspect the cylinder 2 glow plug harness for chafes or shorts. Check the glow plug control module output for cylinder 2. Replace the cylinder 2 glow plug if resistance is low. Clear the code and retest.

P066C

Cylinder 2 Glow Plug Control Circuit Low

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

What it means

P066C means Cylinder 2 Glow Plug Control Circuit Low.

Check these first

A shorted cylinder 2 glow plug pulling the circuit low
A blown fuse in the glow plug control circuit
Corrosion or damage in the cylinder 2 glow plug wiring
A grounding fault in the glow plug harness
A failed glow plug control module

What to do next

Check the glow plug circuit fuse and replace if blown
Test cylinder 2 glow plug resistance against the other cylinders
Inspect the cylinder 2 glow plug harness for chafes or shorts
Check the glow plug control module output for cylinder 2
Replace the cylinder 2 glow plug if resistance is low
Clear the code and retest

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Updated

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