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U049D Invalid Data Received From Glow Plug Control Module 2

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

U049D is logged when a controller, normally the engine control module, still hears from the second glow plug control module but cannot trust what it reports, for instance because a counter, checksum or plug status value is out of line. A second unit is found on diesels that split their glow plugs between two drivers. No manufacturer documents this code publicly; it mirrors U0407, which covers module 1. CARB 1968.2 obliges diesel OBD to verify that glow plugs respond to commands and draw proper current, a check the engine controller can only make with valid module data. A GM patent shows both controllers exchanging timed messages and flagging late ones as faults. U019C means the module is silent, U030B a software mismatch. Hard cold starts and a lit MIL are likely.

Likely causes

Corroded or loose connector or data wire at glow plug module 2
Supply voltage sagging while the glow plugs draw high current
Glow plug control module 2 internally faulty
Module or engine controller software not matched after replacement

Symptoms

  • Check engine or glow plug warning light on
  • Long cranking or misfire on cold starts
  • White smoke until the engine warms up

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€80–600
Time0.5–2.5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

glow plug module 2

Related codes

U019CU030BU0407

References: law.cornell.edu, patents.google.com, en.wikipedia.org.