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U019C Lost Communication With Glow Plug Control Module 2

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

U019C points to a second glow plug control module, needed where a diesel has more preheating channels than one unit drives, for example one module per cylinder bank. No manufacturer documents U019C publicly; it is absent from GM's diesel tables and from the NHTSA bulletin index. The partner code U0106 for module 1 shows the logic: GM's 2015 engine diagnostics table fails it when no GPCM frame has arrived for more than 0.25 s during a 10 s test and rates it Type B. CARB requires glow plugs to be checked for correct current and response to commands, which presumes a live link to the module. The plugs on the affected side may stay cold, giving hard cold starts, rough running and white smoke while warming up; an MIL is to be expected. U049D is invalid data.

Likely causes

Glow plug module 2 without supply, ground or ignition feed
Water or corrosion in the module connector near the engine
Bus line to module 2 chafed or connector loose
Glow plug control module 2 faulty

Symptoms

  • Hard starting when cold
  • White smoke and rough idle until warm
  • Preheat lamp behaves oddly, MIL on

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€50–600
Time0.5–3 h

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

Parts involved

glow plug module 2can bus

Related codes

U0106U049DP0670P0683

References: law.cornell.edu, gsi.ext.gm.com, en.wikipedia.org.