Powertrain, generic · Computer and auxiliary outputs

P0670 Glow Plug Control Module 1 Control Circuit/Open

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

In today's J2012 meaning P0670 is the electrical check of the activation line from the engine module to glow plug control module 1 for an open circuit; a short to ground is P0383, a short to voltage P0384, and serial communication between the modules P0683/P0684. On Bosch systems (Saab 2.2 TiD and EDC16) the engine module switches this line, detects an open load with the output off and a short to voltage with it on, and also compares the glow module's diagnostic feedback, which must switch inversely – Saab reports all line faults under P0670. GM's LB7/LLY Duramax (2004–05) used P0670 in an older meaning for glow module performance (50 of 100 samples, two trips). No current GM or Ford table uses it. If the line fails, no plug heats: hard or no cold start in frost, smoke and rough running.

Likely causes

Wire or connector between engine and glow module open or corroded (bent pin, contact tension)
Glow module faulty (input open) or without supply or ground (fuse, terminal 30)
Control line shorted (makers reporting all line faults under P0670, e.g. Saab)
Output driver in the engine module faulty

Symptoms

  • Check engine light on
  • Glow plug lamp behaves implausibly (stays off or on)
  • Hard or no cold start in frost, since no plug heats
  • Smoke and rough running after a cold start

Repair estimate

DifficultyMediumDIY possible
Parts and labour€50–450
Time0.5–2.5 h

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

Parts involved

glow plug control moduleglow plug control circuitengine control module

Related codes

P0383P0384P0683P0684P064CP0380

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