U0407: Invalid Data Received From Glow Plug Control Module 1
What to do
In warm weather you may notice nothing at all — and that is why this gets ignored until it is expensive.
Glow plugs preheat a diesel's combustion chambers so it will start when cold. Above a certain temperature the engine starts fine without them, so a failed plug is invisible in summer. In winter the same car cranks and cranks, runs roughly with white smoke for the first minute, or does not start at all.
There is a much better reason to act now than the starting, though: glow plugs seize in place. They sit in the cylinder head surrounded by heat and carbon, and a plug left too long can shear off when someone tries to remove it — which turns a routine job into extraction work, and occasionally into removing the cylinder head. The longer it is left, the more likely that becomes.
So treat a code that appeared in summer as a job to do before winter, not after. Usually one plug has failed rather than the module, though they are normally replaced as a set.
What this code means
The glow plug control module is broadcasting data that cannot be accepted as true. See U0400 for the family's framing.
A glow plug module does more than switch the plugs on, and understanding that explains what it reports. Modern systems drive each plug individually, monitor the current each is drawing, adjust the voltage applied to control tip temperature, and continue glowing after the engine has started to reduce cold-running emissions and noise. The module reports plug-by-plug status, and the engine module uses it to decide whether preheating actually succeeded.
An implausible report usually comes from the plugs rather than the module, which is the family's standing rule and is especially true here. Glow plugs are consumables — they fail open with age, and the module reports a current draw that does not correspond to any working plug. One dead plug is enough to make the report unacceptable.
The practical consequence is seasonal in the same way as the fuel heater at P2687, and it deserves the same advice. In warm weather the engine starts perfectly without glow plugs and nothing is noticeable. In winter the same vehicle cranks and cranks, runs roughly and smokes white for the first minute, or does not start at all. So a code that appears in summer with no symptom is a warning issued months early, and acting on it before the cold arrives is the cheap option.
One important repair note, because it turns a moderate job into a very large one: glow plugs seize. They sit in the cylinder head in the combustion chamber, subject to heat and carbon for years, and a plug left in place beyond its life can shear off during removal — which means extraction work with the head in place or, at worst, removing the head. That is the real argument for replacing them when the code appears rather than when the car will not start, and it is worth stating to anybody deciding whether to defer.
Likely causes
Start here
- Faulty heater glow element · moderate
- Open circuit in heater wiring · moderate
- Corroded or loose connector · easy
Less common
- Failed glow plug control module · specialist
- High resistance in heater wiring · 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
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