P06BE: Cylinder 6 Glow Plug Circuit Range/Performance
What to do
Ask for all six plugs to be assessed and make the decision once. They are the same age, access on a six-cylinder engine is usually poor, and removing a glow plug carries a genuine risk of it snapping off in the cylinder head — a risk and a labour bill worth incurring once rather than repeatedly.
Ask for a voltage drop test on the supply under load. This is the last plug on the run, so it feels the accumulated resistance of every connection before it.
Expect hard starting, white smoke and a rough first minute on cold mornings, worsening as the weather cools.
Mention if the plugs have been replaced before and whether they were original parts.
What this code means
Cylinder 6's glow plug circuit is electrically valid but not behaving correctly.
This completes the range/performance set, and it is a reasonable place to summarise how the two glow plug families in this block differ — because the corpus carries both and they are diagnosed differently.
The control circuit codes — P066A, P066C, P066E, P067A — are about the drive to the plug. Low means a short to ground or a failed element; they are electrical faults with electrical causes.
The range/performance codes — P06B9 to P06BE — are about resistance, and therefore about temperature. They catch a plug that still works and no longer heats predictably, which makes them the earlier warning of the two.
A car showing range/performance codes has plugs on the way out. A car showing control circuit codes has one that has arrived.
For this code specifically, on a six-cylinder engine, the last plug on the supply run is where accumulated resistance shows up, so measure the voltage drop under load before condemning the plug.
And make the set decision deliberately. Six plugs, poor access, plugs of the same age, and a real risk of one snapping off in the head — all four facts point the same way, and discovering them one at a time over three visits is the expensive path.
Likely causes
Start here
- Failed glow plug · moderate
- High resistance in sensor wiring · moderate
- Corroded or loose connector · easy
Less common
- Broken glow plug supply wire · moderate
- Failed glow plug control module · moderate
Symptoms
Components involved
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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What makes one worth reading:
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