Powertrain, generic · Ignition system or misfire

P0381 Glow Plug/Heater Indicator Control Circuit/Open

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

P0381 monitors the circuit of the wait-to-start lamp for an open circuit or, more generally, for faults that keep the lamp dark when commanded – CARB names a burnt-out bulb as the example, with exemptions for LCD clusters and for engines that only release the starter after preheating. GM's 2015–2018 diesels detect an open circuit in the driver by a high load impedance (about 200 kΩ in 2015), in 0.2 s or 10 of 15 samples, with the check engine light after two trips; on the 2014 Duramax LML P0381 still covered all lamp circuit faults including a short to ground. Ford's 2023 diesels check via the instrument cluster: if it reports the lamp off although on is commanded, P0381 is set within about 1 s at key-on. There is no limp mode; the risk is starting too early in the cold.

Likely causes

Control wire open or connector fault between engine module and cluster
Lamp or LED in the instrument cluster burnt out
Instrument cluster faulty or communication problem (Ford)
Driver in the engine module

Symptoms

  • Glow plug light does not come on at key-on
  • Check engine light on (GM after two trips)
  • Driver starts too early in the cold

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€50–500
Time0.5–2.5 h

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

Parts involved

glow plug indicatorindicator wiringinstrument clusterengine control module

Related codes

P037AP037BP0380P0670U0106

References: gsi.ext.gm.com, gsi.ext.gm.com, gsi.ext.gm.com, fordservicecontent.com.