What Does P066E Mean?
The PCM has detected a low voltage condition in the glow plug control circuit for cylinder 3 on a diesel engine. This indicates a short to ground or excessive current draw from the cylinder 3 glow plug circuit. The glow plug may be drawing abnormally high current due to internal degradation, or the wiring may have shorted to the engine block. The driver may notice slightly harder cold starts and the possibility of blowing the glow plug circuit fuse.
Common Causes
35%
Short to ground in cylinder 3 glow plug wiring
30%
Failed cylinder 3 glow plug with internal short
20%
Corroded bus bar or terminal creating low-resistance ground path
10%
Glow plug control module overcurrent protection triggered
5%
Wiring insulation melted from exhaust heat contact
Diagnostic Steps
1
Disconnect the cylinder 3 glow plug and measure its resistance. Spec is typically 0.5-2.0 ohms — a near-zero reading indicates an internal short.
2
With the glow plug disconnected, test for continuity between the control wire and engine ground. Continuity without the glow plug connected proves a harness short to ground.
3
Inspect the bus bar and wiring around cylinder 3 for heat damage, corrosion, carbon tracking, or wire-to-metal contact. The cylinder 3 location is often near turbocharger plumbing on many diesels.
4
Using a clamp-on DC ammeter on the cylinder 3 feed wire, measure current during glow cycle. Compare to other cylinders — significantly higher current confirms the shorted component.
5
If the glow plug and wiring are good, monitor the glow plug control module output for cylinder 3 — if it shows a fault even with a known-good load, the module driver is damaged.
Estimated Repair Cost
$80 - $400
Parts + labor, varies by vehicle and location
The PCM has detected a low voltage condition in the glow plug control circuit for cylinder 3 on a diesel engine. This indicates a short to ground or excessive current draw from the cylinder 3 glow plug circuit. The glow plug may be drawing abnormally high current due to internal degradation, or the ...
The most common cause of P066E (Cylinder 3 Glow Plug Control Circuit Low) is: Short to ground in cylinder 3 glow plug wiring
Typical repair costs for P066E range from $80 to $400, depending on the vehicle, location, and whether you do it yourself or go to a shop.
A shorted circuit can damage the glow plug control module or blow protective fuses, potentially disabling all glow plugs. This could make cold starting impossible in winter. Repair within a week to prevent cascading failures in the glow plug system.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P066E to identify the root cause.
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Quick Info
Category
Powertrain
System
Diesel Glow Plug System
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
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