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DTC code page

P0670: Glow Plug Control Module Control Circuit

Quick answer: The ECU detected a fault in the glow plug control module circuit rather than one single cylinder plug.

Drivers also search this fault as glow plug module control circuit, glow plug control module fault, diesel preheat module code.

Severity: medium Family: powertrain Related paths: 11
Meaning

What P0670 usually means

P0670 points higher up the diesel preheat chain than an individual cylinder code. Instead of singling out one plug, it suggests the control module, relay logic, or module communication path is not operating normally. That matters because a module-side fault can make several cylinders slow to light at once, creating a hard start that feels like weak compression or fuel trouble when the root issue is actually the preheat command path.

Fast triage

Start here before chasing parts

  • Scan first: save freeze-frame and pending codes before clearing anything.
  • Confirm the complaint: compare the stored code with current drivability symptoms.
  • Use context: trims, live data, and related codes usually narrow the fault faster than guesswork.
  • Work simplest to hardest: leaks, connectors, maintenance items, and known patterns before expensive components.
Initial checks

What to check first

  • Verify the module has clean battery feed and ground before condemning it.
  • Look for evidence of moisture, overheating, or corrosion at the controller connector.
  • Compare scan-tool commanded preheat with actual output behavior if the platform supports it.
Driving risk

Can you keep driving?

P0670 mainly affects cold-start reliability. If the engine is already hard to light or smokes heavily on cold starts, repair it before the next temperature drop makes the vehicle unreliable.

Moderate urgency: This code often allows short-term driving, but the right fix usually comes faster when you diagnose it early instead of waiting for more codes.
Likely causes

Common causes behind this code

  • Failed glow plug control module
  • Missing power or ground at the control module
  • Damaged communication or command wiring to the module
  • Corroded module connector or overheated terminal
  • Water intrusion into the module housing or connector

Cause phrases often tied to this code: glow plug controller, module power feed, relay logic fault, bad module ground, wiring issue.

Diagnostic order

Suggested workflow

  1. Confirm P0670 and capture freeze-frame or temperature context.
  2. Check module power supply, ground integrity, and main fuse condition.
  3. Inspect command and feedback wiring between the PCM and glow plug controller.
  4. Test whether the module is delivering output to the glow plug circuits during pre-glow.
  5. Repair the circuit or replace the failed module only after supply and wiring are proven.
Avoid guesswork

Common mistakes

  • Replacing cylinder glow plugs when the controller is not driving them correctly in the first place.
  • Skipping module ground checks because battery voltage appears present on the feed side.
  • Assuming every cold-start smoke complaint is injector-related on a diesel.
Repair path

Practical fix guidance

  • Restore clean power, ground, and command integrity to the glow plug control module.
  • Replace the module only after confirming the fault is not external wiring or connector damage.
  • Retest on a cold engine so the repair is validated under the exact conditions that set the code.
Vehicle context

Affected brands in this MVP

Brand hubs help broaden internal linking now and can evolve into make-specific diagnostic notes later.

Aliases and common searches

English phrases tied to P0670

Useful when the driver knows the wording but not the exact DTC yet.

  • glow plug module control circuit
  • glow plug control module fault
  • diesel preheat module code
Related search intent

Queries this page can answer naturally

  • P0670 code meaning
  • what does P0670 mean
  • glow plug control module symptoms
  • diesel preheat module failure
FAQ

Quick questions about P0670

Is P0670 the same as a bad glow plug?

No. P0670 usually points to the controller or its circuit, not automatically to one failed plug.

Can P0670 affect more than one cylinder at once?

Yes. A controller fault can reduce or remove preheat for multiple cylinders together.

Why can P0670 mimic fuel-system trouble?

Because poor preheat creates rough cold combustion, smoke, and long crank that feel similar to fuel-delivery problems.