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Generic light-duty diesel DTC / Cold-start assistance

P0670: Glow Plug Control Module Control Circuit

Generic definition: Glow Plug Control Module Control Circuit

The controller detected a concern in the glow-plug control-module circuit. Power, ground, command, communication, module, or downstream heater faults can overlap; this code does not confirm module failure.

Generic definition
P0380

Likely cause paths · unconfirmed

A possible control-module power, ground, or command fault

The module may lack a valid supply or command, or its circuit may have a connection problem.

  • Save related voltage or communication codes.
  • Note recent battery or electrical repairs.

A possible module or downstream heater fault

A module fault or a short/open in its output load may set this code; testing must separate them.

  • Record any P0380 or cylinder-specific glow codes.
  • Do not install a module based on this code alone.

Module pinouts and output tests are vehicle-specific and technician-only. Generic thresholds are not provided.

Conditional repair directions

A code is not a parts recommendation. Follow a direction only after the listed evidence confirms its cause.

If confirmed: A possible control-module power, ground, or command fault

Restore the confirmed supply, ground, connector, or command path, then rerun the maker’s module check.

Evidence to confirm

  • The OEM circuit procedure identifies the missing or faulty input.
  • Module operation and the required cold-start check pass after correction.

If confirmed: A possible module or downstream heater fault

Replace the module or repair an output circuit only after testing isolates that part of the system.

Evidence to confirm

  • The module fails its specified test with verified inputs and loads, or an output circuit fails independently.
  • Related glow-circuit codes do not return after verification.

Ordered evidence checks

  1. 01

    Preserve module and companion codes

    Record exact status, glow indicator behavior, cold-start conditions, and related codes before clearing.

  2. 02

    Note battery and cranking behavior

    Record slow cranking, recent battery replacement, or jump-start history. Do not bridge terminals or disconnect a running battery.

  3. 03

    Check for visible damage from a safe position

    After shutdown and cooling, look only for obvious harness damage or water intrusion near accessible connectors. Do not unplug or probe them.

  4. 04

    Verify module command and circuit supply

    Qualified technician / OEM procedure

    A qualified technician should follow the OEM wiring and scan-tool procedure for module power, ground, command, output, and downstream circuits.

Possible symptoms

  • Cold hard start or extended cranking
  • Rough idle during warm-up
  • Glow-plug circuit codes or an indicator concern

The DTC definition is generic; the app’s cause paths are unverified, do not establish a failed part, and are not OEM procedures. Confirm vehicle-specific tests with the maker’s service information or a qualified technician.