U0407 — Invalid Data Received – Glow Plug Control Module #

Note: The wording of this DTC (Diagnostic Trouble Code) may vary depending on the vehicle manufacturer. Always refer to your specific OEM (Original Equipment Manufacturer) documentation for precise descriptions.

• Invalid Data Received From Glow Plug Control Module (Ford, GM, Chrysler)
• Glow Plug Control Module: Implausible Data (Volkswagen/Audi)
• Glow Plug Control Unit – Incorrect Data (Mercedes-Benz)

Summary of Code U0407 #

The U0407 trouble code signals that the vehicle’s control module—usually the Engine Control Module (ECM)—has detected invalid or implausible information coming from the Glow Plug Control Module. Glow plugs are heating elements used in diesel engines to aid cold starting and emissions control. This code typically points to a communication issue on the vehicle’s data network, known as the CAN bus (Controller Area Network). The root cause can range from electrical faults to software mismatches. While U0407 doesn’t always mean a glow plug has failed, it does mean the data exchange between modules isn’t reliable, which can impact cold starts and emissions. Prompt attention is recommended to prevent further complications, especially in colder climates.

Common Symptoms for Code U0407 #

A vehicle experiencing U0407 may present subtle or obvious signs, depending on the severity of the communication problem. Diesel engines are particularly sensitive to glow plug system faults, especially during cold starts. Watch for the following:

• Hard starting or extended cranking in cold weather
• Glow plug warning light illuminated on the dashboard
• Check engine light (MIL – Malfunction Indicator Lamp) on
• Rough idle immediately after start
• Possible decrease in engine performance during warm-up
• Temporary increase in exhaust smoke on cold starts

Probable Causes for Code U0407 #

When U0407 appears, the most common culprits are issues within the vehicle’s data network or the glow plug control system itself. Address these in order of likelihood:

1. Poor electrical connections at the glow plug control module or related harnesses
2. Faulty glow plug control module sending corrupted or implausible data
3. Wiring issues—damaged wires, corroded connectors, or poor grounds in the CAN bus circuit
4. Software incompatibility due to recent module replacement or programming
5. Faulty Engine Control Module (ECM) (rare, but possible if all other causes are ruled out)

Step-by-Step Diagnosis for Code U0407 #

Diagnosing U0407 requires a methodical approach. This is not just about replacing glow plugs; it’s about verifying the integrity of communications between modules. Here’s a proven workflow:

• Step 1: Use a professional scan tool to confirm the presence of U0407 and check for related codes. Document freeze frame data.
• Step 2: Visually inspect the glow plug control module and all related connectors for signs of corrosion, water intrusion, or loose pins.
• Step 3: Test the continuity and resistance of the wiring harness between the ECM and the glow plug control module, focusing on CAN high and CAN low circuits.
• Step 4: Check for technical service bulletins (TSBs) or OEM software updates addressing communication faults for your vehicle.
• Step 5: If wiring and software are in good order, use a known-good module for substitution testing, if possible, to rule out a defective glow plug control module.
• Step 6: As a last resort, consider ECM diagnosis or replacement if all tests above pass but the code persists.

Possible Repairs for Code U0407 #

The correct repair depends on the root cause identified during diagnosis. Always clear codes and perform a road test after repairs to confirm resolution. Typical solutions include:

• Repairing or replacing corroded connectors at the glow plug control module
• Fixing or replacing damaged wiring in the CAN network between modules
• Updating or reprogramming module software per OEM recommendations
• Replacing the glow plug control module if internal faults are confirmed
• Replacing the ECM (only if all other steps fail and with proper OEM programming)

Is It Safe to Drive with Code U0407? #

Driving with U0407 is possible, but not recommended, especially in cold climates. The engine may have difficulty starting or run rough during warm-up. Additionally, emissions may be affected. Prolonged driving with this code can lead to more severe problems, including potential damage to emission components. Address the issue as soon as possible to avoid being stranded or causing further damage.

Vehicles Most Commonly Affected by Code U0407 #

This code is most frequently reported on modern diesel vehicles equipped with electronically-controlled glow plug systems. Some commonly affected vehicle types include:

• Ford F-Series diesels (Power Stroke engines)
• Chevrolet Silverado/GMC Sierra Duramax diesels
• Dodge Ram Cummins diesels
• Volkswagen/Audi TDI models
• Mercedes-Benz Sprinter vans
• BMW diesel models

Common Mistakes & Best Practices for Code U0407 #

Avoid the temptation to jump straight to glow plug replacement. Since U0407 is a communication code, not a direct component failure, misdiagnosis is common. Keep these tips in mind:

• Don’t replace glow plugs without verifying the control module and wiring first
• Avoid clearing codes before recording freeze frame data—this information can be vital
• Always check for technical service bulletins (TSBs) related to module communication
• If a module is replaced, ensure proper programming and initialization per OEM procedures
• Inspect for signs of water intrusion or rodent damage in engine bay wiring

U0407 FAQ #

Here are some quick answers to common questions about U0407:

• Q: Does U0407 mean I have a bad glow plug?
  A: Not directly. U0407 indicates a communication problem with the glow plug control module, not the plugs themselves. However, unresolved communication errors may prevent the system from operating glow plugs correctly.
• Q: Can a weak battery trigger U0407?
  A: Rarely. While a weak battery can cause voltage issues and erratic module behavior, U0407 typically points to data integrity or communication problems, not low voltage alone.