P0670 code meaning
Glow Plug Control Module 1 Control Circuit/Open
Powertrain system Generic code P06xx codes Check engine light
What P0670 means
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.
P0670 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium, DIY possible
- Typical labor0.5 to 2.5 hours
- Clears after repairAfter a drive cycle
Symptoms of P0670
- 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
Common causes of P0670
- Most likelyWire or connector between engine and glow module open or corroded (bent pin, contact tension)
- PossibleGlow module faulty (input open) or without supply or ground (fuse, terminal 30)
- PossibleControl line shorted (makers reporting all line faults under P0670, e.g. Saab)
- Less likelyOutput driver in the engine module faulty
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Glow plug control moduleGlow plug control circuitEngine control module
What each part of P0670 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 6 | Area: computer (engine control module) and output circuits. |
| 70 | The exact fault in that area. |
What to do next
- Note P0670 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0670
What does P0670 mean?
P0670 means "Glow Plug Control Module 1 Control Circuit/Open". 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. It is a generic code, so it means the same on every make.
Is it safe to drive with P0670?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P0670 fail an emissions test?
Yes, it can. P0670 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0670 to fix?
Difficulty: medium. A typical repair takes 0.5 to 2.5 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P0670 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.