U0407
Invalid Data Received From Glow Plug Control Module
- Severity
- High
- Driving
- Drive only to a garage
The glow plug control module is sending data that the module storing this code can tell is wrong. The message is arriving, so the network and the wiring between them are working - but something in it fails a plausibility check: a value outside the range it could physically take, a failed checksum, or a message counter that stopped advancing. That is what separates this from a lost communication code, where the message stops arriving altogether. This code is stored by the module *receiving* the data and it names the module that *sent* it, so it points away from itself. The fault is usually in the glow plug control module, or in a sensor feeding it, rather than in the module that noticed. Powertrain modules share torque, speed and load figures constantly, and each one sanity-checks what the others send. A value that fails those checks makes the receiving module fall back to a conservative default, which is why the car usually still drives but drives badly.
Possible causes
- CommonA fault inside the glow plug control module, or in a sensor feeding it, so it passes on a reading that is wrong
- CommonThe glow plug control module has its own stored fault codes that explain why its data is bad
- CommonLow or unstable system voltage - a module starved of a steady supply produces nonsense values
- CommonCorroded or water-damaged connector at the glow plug control module, corrupting the message content
- PossibleSoftware or calibration mismatch after the glow plug control module was replaced, updated or coded
- PossibleDamaged wiring, or a repair that disturbed the bus pair
- PossibleInterference from a badly-fitted aftermarket accessory spliced into the bus
- RareA fault in the receiving module, which is misjudging data that is actually good
What you might notice
- Limp mode - reduced power, or the gearbox locked in one gear
- Harsh or unpredictable gear changes
- Poor starting, or the engine cutting out
- Check engine light on
- Warning light on for the system that depends on the data
- The affected function switching itself off
- Fault codes stored in more than one module
What to check, in order
- Read the codes from every module on the vehicle, not just the engine. This code names the glow plug control module as the source, and the glow plug control module almost always has its own code saying why its data is wrong. That code, not this one, is the one to fix.
- Check battery voltage and the earth points before suspecting any module. A supply that sags makes modules produce implausible values, and it sets invalid-data codes across several unrelated systems at once.
- If more than one module is reporting invalid data, look at the power supply and the bus rather than at the modules. Modules do not fail in groups; shared feeds, earths and bus wiring do.
- Find out whether anything was recently fitted, replaced, updated or coded. A replacement module carrying the wrong calibration sends data in a range or format the rest of the vehicle does not expect, and this code is often the first sign of it.
- Inspect the connector at the glow plug control module for corrosion and water ingress. A partly-corroded pin corrupts the content of a message while the message itself still arrives on time - which is precisely this code rather than a lost communication code.
- Do not replace the glow plug control module on the strength of this code alone. It is the accused, not the convicted. Confirm the data it is sending is actually wrong - by reading its own codes and its live data - before spending money on it.
Read this code from your own car
Plug an ELM327 adapter into the OBD-II port under the dashboard. Pin16 reads every stored, pending and permanent code, explains each one like this page does — offline, with no account — and shows what the car recorded when the fault was set.