What Does P068E Mean?
The PCM has detected a low voltage condition on the cylinder 8 glow plug control circuit. This indicates a short to ground in the glow plug or its wiring for cylinder 8. The glow plug may be drawing excessive current, which can overload the GPCM. The driver may notice difficult cold starts, rough idle during warmup, and white smoke from the exhaust.
Common Causes
40%
Cylinder 8 glow plug shorted internally to ground
25%
Short to ground in the harness between GPCM and cylinder 8
20%
GPCM output driver failure for cylinder 8 channel
10%
Water intrusion or corrosion at the cylinder 8 connector
5%
PCM monitoring circuit fault
Diagnostic Steps
1
Measure cylinder 8 glow plug resistance; near-zero ohms confirms an internal short. Normal range is 0.3-2.0 ohms depending on application.
2
With the glow plug disconnected, measure the harness wire from GPCM to cylinder 8 for resistance to ground; should be OL (open/infinite).
3
Visually inspect the wiring to cylinder 8, particularly where it routes near exhaust manifolds, turbo downpipes, or other heat sources on the rear of the engine.
4
Activate the GPCM with cylinder 8 disconnected and verify battery voltage output at the GPCM connector for that channel.
5
Compare current draw of cylinder 8 to adjacent cylinders using a current clamp; a significantly higher draw confirms a partial short in the plug.
Estimated Repair Cost
$75 - $450
Parts + labor, varies by vehicle and location
The PCM has detected a low voltage condition on the cylinder 8 glow plug control circuit. This indicates a short to ground in the glow plug or its wiring for cylinder 8. The glow plug may be drawing excessive current, which can overload the GPCM. The driver may notice difficult cold starts, rough id...
The most common cause of P068E (Cylinder 8 Glow Plug Control Circuit Low) is: Cylinder 8 glow plug shorted internally to ground
Typical repair costs for P068E range from $75 to $450, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to drive once the engine is warmed up. Excessive current draw from a shorted glow plug can damage the GPCM or blow the glow plug system fuse, which would disable all glow plugs. Repair to prevent cascading failure.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P068E to identify the root cause.
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Quick Info
Category
Powertrain
System
Diesel Cold Start / Glow Plug System
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
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