U049D: Invalid Data Received From Glow Plug Control Module 2

What it means

A control module received invalid data from glow plug control module 2. The code identifies a data validity fault; the specific affected function depends on the vehicle.

At a glance

• Usually lights the warning light of the system that lost communication
• Affects emissions; the car can fail an emissions test

How it works

Glow plug control module 2 manages the second glow-plug control unit identified by the vehicle and reports its status to other modules. U049D sets when a receiving module judges data from module 2 invalid; on a diesel engine, this can interfere with cold-start assistance.

Common causes

Most likely first.

1. Fault in the transmitting module
2. Network wiring or connector fault
3. Module power or ground fault
4. Software or configuration mismatch

Symptoms

• Cold starting may be more difficult
• Engine or glow-plug warning may appear

How to diagnose it

1. Use a scan tool to record freeze-frame data and check for glow-plug or diesel-engine codes that may help distinguish a data fault from a separate heater fault.
2. Check whether U049D returns and review glow-plug status data, especially after a cold start when module 2 is expected to report.
3. Inspect glow plug control module 2's connectors and network wiring for looseness, corrosion, damage, or chafing.
4. Check module 2 power and ground using the manufacturer's diagnostic procedure, since a supply fault can invalidate its reports.
5. If wiring and supplies are sound, use vehicle-specific tests to assess module 2 and verify software and configuration.

Common fixes

• Reconnect or clean a loose or corroded glow plug control module 2 connector.
• Repair damaged network wiring to module 2.
• Repair a poor module 2 power or ground connection.
• Correct software or configuration if vehicle-specific service information calls for it.
• Replace glow plug control module 2 if testing confirms it is faulty.

Can I keep driving?

Cold starting may become difficult, especially in low temperatures, and repeated extended cranking can strain the starter and battery. Arrange diagnosis soon; if the engine runs roughly or an engine warning flashes, stop driving and seek help.