OBD-II trouble code
U0407: Invalid Data Received From Glow Plug Control Module 1
A module is receiving messages from the glow plug control module on a diesel engine, but the data is implausible or out of range. The usual result is hard cold starting and a glow plug warning light. A diesel-only code — the connection is alive, the content is wrong.
Quick facts
- System
- Network
- Category
- Network Communication
- Severity
- Medium severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $100 – $900
- DIY difficulty
- Shop recommended
What does U0407 mean?
Diesel engines rely on glow plugs to preheat the combustion chambers for cold starting, and on modern diesels a dedicated glow plug control module manages them — timing the preheat cycle, switching the high current the plugs draw, monitoring each plug's circuit, and reporting status to the engine control module over the network. U0407 sets when a receiving module is still hearing from the glow plug control module, but the data inside its messages is invalid: reported currents, temperatures, or status values that are out of range or contradict other information. This is distinct from lost communication (U0106), where the module goes silent entirely.
The causes cluster around what makes the module report untrustworthy numbers. Failed or failing glow plugs are the most common trigger — a shorted plug pulls implausibly high current, an open plug reports none at all, and either can push the module's data out of the plausible window. The module itself is a known wear item on many diesels because it switches heavy current and often lives in a hot, harsh under-hood location; internal degradation produces exactly the kind of drifting, inconsistent data this code describes. Low battery voltage during cold cranking, corroded high-current connections, and corrupted or mismatched module software complete the usual list.
Symptoms center on cold starting: long cranking, rough running and white smoke until the engine warms, a glow plug (coil symbol) warning light, and in cold climates a possible no-start. Once the engine is warm the vehicle typically runs normally, which tempts people to ignore the code through summer — but unresolved glow plug faults reliably resurface as no-starts on the first cold morning of the year.
Common causes
- One or more failed glow plugs (shorted or open) skewing the module's reported data
- Degraded glow plug control module — a known wear item switching high current in a harsh location
- Low battery voltage during cold cranking
- Corroded or loose high-current connections at the module or glow plug harness
- Outdated, corrupted, or mismatched glow plug module software
- Module replaced without proper programming
- Heat or vibration damage to the module or its wiring
- Bus wiring problems corrupting messages in transit
Symptoms
- Hard starting or long cranking when the engine is cold
- Glow plug warning light (coil symbol) on or flashing
- White or gray smoke at cold start until the engine warms
- Rough idle for the first minutes of cold operation
- Possible no-start in freezing weather
- Normal running once warm in most cases
- Companion glow plug circuit codes (P0670-series) stored alongside U0407
Diagnostic steps
- 1.Read ALL stored codes — companion glow plug circuit codes (P0670-P0684 range) usually identify which plug or circuit is at fault.
- 2.Load-test the battery and check charging voltage; diesels demand strong cranking voltage and weak batteries skew glow plug data.
- 3.Test each glow plug's resistance or current draw — shorted or open plugs are the most common trigger for implausible module data.
- 4.Inspect the module's high-current connections and harness for corrosion, heat damage, or looseness.
- 5.Verify the glow plug control module has correct, current software, especially after replacement.
- 6.If plugs and wiring test healthy and data remains implausible, replace the glow plug control module and confirm normal preheat operation on a cold start.
Repair cost
$100 – $900
Individual glow plugs run $15-$50 each plus labor, though on some engines seized plugs make replacement labor-intensive ($200-$600 for a set, more if a plug breaks off in the head). A replacement glow plug control module typically runs $150-$450 installed. Software corrections run $100-$300. Address plugs and module together when both are marginal — a new module driving failed plugs won't cure the cold-start complaint.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with module communication / can bus diagnosis preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
Leave this one to a qualified shop. It typically involves emissions-critical components, refrigerant handling, or other work that requires manufacturer-grade tooling, training, or certification. DIY attempts often produce a more expensive problem than the original code.