Powertrain, generic · Ignition system or misfire

P0383 Glow Plug Control Module 1 Control Circuit Low

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

Many diesels have a separate glow plug control module that the engine module commands over a control line. P0383 means this line is too low. In GM's logic for the 2010/11 Saab 9-5 2.0 TiD the engine module drives the module with a PWM signal and holds about 10 V on the line at rest (9.5–10.5 V at the signal terminal); if it reads too little voltage for more than 0.5 s – short to ground, or an open circuit or high resistance – it sets P0383, with ignition on, 9–16 V, once per ignition cycle. In that European version the code does not turn on the check engine light. Without a valid command the module does not glow, so the engine starts poorly when cold. Ford uses P0384 differently and not P0383; GM's 2016/2018 diesels have their output stages in the engine module and no such line. For US vehicles there is no code-specific source.

Likely causes

Control line between engine module and glow plug module shorted to ground or open
Corroded connector at the glow plug module in the engine bay
Glow plug control module faulty (input pulls the line down)
Driver in the engine module

Symptoms

  • No preheating, poor cold start
  • Smoke after a cold start
  • Warning lamp depending on the manufacturer

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€80–450
Time0.5–2 h

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

Parts involved

glow plug control module 1module wiringengine control module

Related codes

P0384P0670P0683P0684P0380

References: saabwisonline.com, saabwisonline.com, law.cornell.edu.