P0670

Glow Plug Control Module 1 Control Circuit/Open

Glow plugs (diesel) Generic OBD-II High

What it means

P0670 is a diesel code meaning the ECM has detected an open in the control circuit for the glow plug control module. Glow plugs pre-heat the cylinders so a cold diesel will light off; when the module's circuit is open, that pre-heating fails and cold starts become hard, smoky, and rough. It normally points at the module or its wiring, not at the engine internals.

High

Can I keep driving? The engine usually still runs, but cold starts can be hard, smoky, and rough until the glow-plug system is fixed — worse the colder it gets.

Real-world scan data

Seen in

2,260

scans in the past year

Found in

0.4%

of scans

0.6%

of scans that found faults

Appears alongside · share of P0670 scans

P0380in 47.0% of scans

P0850in 18.7% of scans

P0704in 18.6% of scans

Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.

Common symptoms

What you'll notice

Check-engine light on (and often a glow-plug/wait-to-start light)
Hard starting, especially in cold weather
Rough running and white exhaust smoke on a cold start
Misfire-like shake until the engine warms up

Common causes

Most likely first

Faulty glow plug control moduleLikely
Open or damaged wiring/connector in the module's control circuitCommon
Corroded or loose glow-plug harness connectionsCommon
Failed engine control module (ECM) driving the glow-plug moduleLess often

How to diagnose & fix

Work through it in order

Scan and record freeze-frame data, then confirm whether the module or its control wiring is open.
Inspect the glow-plug control module connector and harness for corrosion, damage, or an open circuit; repair as needed.
Check the module's power and ground feeds before condemning the module itself.
If wiring and feeds are good, replace the glow plug control module and re-test cold-start behaviour.

FAQ

Quick answers

Is it safe to drive with P0670?+

You can usually drive once started, but cold starts will be hard and smoky. Fix it before winter, since a dead glow-plug system can leave you unable to start on a cold morning.

Can I just clear P0670?+

It clears, but returns as soon as the module or its wiring fails again. Repair the open circuit first.

Read & clear P0670 yourself

Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.

▶ Get it on Google Play

✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX