Drivers first notice the problem when the engine refuses to start or struggles to turn over. In diesel‑powered vehicles the P0672 code triggers the check‑engine light and is most apparent in cold‑weather conditions when the glow‑plug system is needed for combustion. Typical observations include:
These symptoms arise because cylinder 2 is not receiving the pre‑heat voltage it needs to ignite the air‑fuel mixture during cold starts.
A glow plug that has burned out or developed an internal short will present an open circuit to the ECM. When the plug cannot draw current, the ECM registers a loss of continuity and stores P0672.
Corroded terminals, broken wires, or loose connectors in the glow‑plug harness can interrupt the circuit. Vibration, exposure to coolant, or water ingress are common sources of intermittent opens.
The ECM (or PCM) controls the glow‑plug circuit through a dedicated driver transistor. If that driver fails, the module cannot supply the required 12 V to the plug, even when the plug itself is functional. Because the ECM is the source of the voltage, a driver fault registers the same “circuit/open” condition.
Occasionally, the control module’s calibration data for glow‑plug timing can become corrupted, causing the module to incorrectly interpret a healthy circuit as open. Re‑programming the module often resolves this issue.
Use an OBD‑II scanner capable of reading manufacturer‑specific data. Confirm that P0672 is present and note any accompanying codes (e.g., P0673 for cylinder 3) that may indicate a broader harness problem.
Locate the cylinder 2 glow‑plug connector. Check for corrosion, cracked insulation, or loose pins. Ensure the connector is securely seated on the plug.
With the key in the “on” position (engine not cranking), measure voltage between the glow‑plug terminal and ground. A healthy circuit should show ~12 V. Absence of voltage points to an open upstream of the plug.
Disconnect the plug and perform a resistance test on the wiring from the ECM to the connector. Infinite resistance confirms an open circuit; low resistance (< 1 Ω) indicates a short to ground.
If the wiring checks out and voltage is absent, the driver inside the ECM is suspect. Some diagnostic tools can command a “glow‑plug test” that forces the driver on; monitor voltage response. Failure to produce voltage confirms a module fault.
– Glow plug or wiring repair – replace the plug or repair the harness if the fault lies outside the module.
– ECM/PCM repair – board‑level repair may be possible but is often temporary.
– ECM/PCM replacement – a new, VIN‑matched module ensures correct hardware and software. Re‑programming to the vehicle’s specifications is required.
After installing a replacement ECM, the unit must be programmed with the vehicle’s calibration data (fuel maps, glow‑plug timing, immobilizer keys). This step restores full functionality and clears the P0672 code.
Cost considerations
If the ECM’s glow‑plug driver fails, repair attempts often provide only a temporary fix. The driver circuit is integrated into the module’s power‑stage architecture; once damaged, it can cause intermittent faults that reappear after exposure to heat or vibration. A replacement guarantees a clean, tested driver and eliminates the risk of recurring P0672 codes.
Flagship One specializes in VIN‑matched control modules. Modern control modules are complex, integrating engine management, security, and immobilizer functions. Selecting a replacement isn’t just about hardware—it requires precise programming to match the vehicle’s VIN and software version. Flagship One provides plug‑and‑drive modules that are pre‑programmed, backed by a warranty, and tested for reliability, ensuring a seamless swap without dealer‑level delays.
Service Recommendation: Most issues related to this fault are diagnosed and corrected through inspection, wiring repair, and calibration rather than module replacement. For modules not typically replaced through aftermarket suppliers, diagnosis and repair should be performed by a certified automotive technician with access to factory service information and tooling.