P067A: Cylinder 4 Glow Plug Control Circuit Low
What to do
If plugs are coming out, have all four done. They are the same age, access is most of the cost, and removing a glow plug carries a genuine risk of it snapping off in the cylinder head — a risk worth taking once rather than four times.
Talk about that risk before the work starts, and expect a careful garage to want to soak the plugs and heat-cycle the engine first.
Expect hard starting, white smoke and a rough first minute on cold mornings until it is repaired.
Ask for the glow plug control module to be tested as well, since a shorted plug can damage its driver and the fault would return.
What this code means
The control circuit for cylinder 4's glow plug is sitting lower than commanded.
Note the code number, because it is the one this family gets wrong. Cylinders 1 to 3 are at P066A, P066C and P066E — stepping in twos — and cylinder 4 is at P067A, not the next number in that sequence. The pattern breaks because the intervening numbers hold the high-side versions of the same circuits.
Read the cylinder from the code rather than counting from a neighbouring one. Assuming the stride continues puts the diagnosis on the wrong cylinder, and on a four-cylinder diesel that is the last plug in the row.
The mechanism is the family's: a plug failed short, a supply strap chafed against the head, or a driver already damaged inside the control module.
On a four-cylinder engine this completes the set, which makes it a good moment to make the set-versus-single decision rather than defer it. Access is most of the labour, the plugs are the same age, and the removal carries a real risk of a plug snapping off. Doing all four while the engine is open is usually better value and, more importantly, avoids taking that risk twice.
Measure the plug before condemning the module. A short here can destroy a driver, and a replacement module fitted without finding it fails the same way.
Likely causes
Start here
- Failed glow plug · moderate
- Wiring shorted to ground · 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
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
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
Be the first to write this up
Nothing posted about this yet. Whatever you found is worth writing down — even a dead end saves someone the same afternoon.
What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
Sign in or create an account to add what you found about P067A.