P0670
Glow Plug Module Control Circuit
If your code reader dashboard displays the generic DTC error code P0670, your vehicle is currently experiencing an active failure related to "Glow Plug Module Control Circuit". Proper system troubleshooting is required to safely clear this warning.
Driver's Summary
The diagnostic trouble code P0670 indicates an active fault in the glow plug module control circuit circuit or component. The most common signs are hard starting in cold weather, check engine light on, white smoke on startup. You can typically drive short distances, but ignoring this code long-term will cause accelerated component wear and higher repair costs.
Symptoms
Hard starting in cold weather, check engine light on, white smoke on startup
Common Causes
- Failed glow plug control module
- Open or shorted control circuit wiring
- Blown glow plug module fuse
- Corroded ground connection
How to Fix
- 1 Test and replace glow plug control module
- 2 Repair damaged wiring harness
- 3 Replace blown fuses
- 4 Clean main ground cables
Technical Explanation
P0670 is stored after the control module confirms the fault over multiple ignition cycles, ruling out transient electrical noise as the cause. The PCM distinguishes between electrical faults (circuit codes) and performance faults (rationality codes) by comparing the sensor's reported value against what other sensors would predict under the same engine operating conditions. After two failed drive cycles, the code transitions from a pending to a confirmed DTC, and the PCM activates the MIL. Clearing the code without repairing the fault will result in re-illumination within one to two complete drive cycles.
Is It Safe to Drive?
You can drive short distances, but the symptoms — hard starting in cold weather, check engine light on, white smoke on startup — indicate the affected system is compromised. Leaving this unresolved will lead to progressively worse fuel economy and potential damage to components beyond the original fault.
Mechanic's Pro Tip
Before replacing any component on P0670, spend 5 minutes inspecting the wiring harness and connector first — corrosion, chafed insulation, and backed-out pins cause the majority of these faults and cost nothing to fix. Use a multimeter to measure voltage drop across the connector pins under load; anything above 0.1V indicates excessive resistance that will cause intermittent failures even after replacing the sensor.
Glow plug module: $200 - $500