P0672

What P0672 Means

Code P0672 points to a fault in the glow plug circuit for cylinder 2. The engine management system (DME) detects a deviation in the glow plug or its electrical circuit, which can be caused by a faulty glow plug, wiring problems, or a failed glow plug control module.

Glow plugs heat the combustion chamber of a diesel engine before startup, especially in cold weather. The Glow Plug Control Module regulates voltage to each plug based on operating conditions. When a fault occurs in the cylinder 2 circuit, the DME sets code P0672 and may limit voltage to that plug, which leads to hard cold starts and higher exhaust emissions.

Symptoms

• Warning light: the Check Engine Light (CEL) comes on in the instrument cluster.
• Engine startup: worse cold starts (the engine may be slow to fire or need extended cranking by the starter motor).
• Engine operation: rough idle after a cold start, possible misfires.
• Emissions: higher emission levels from incomplete combustion in cold mode.

Symptoms are most pronounced in low ambient temperatures and after long periods parked.

Diagnosis and Repair

Step 1: Read Fault Codes

Use BMW diagnostic equipment (ISTA, INPA) to confirm code P0672 and check for related faults on other cylinders or the glow plug control system.

Step 2: Check the Cylinder 2 Glow Plug

• Disconnect the connector from the cylinder 2 glow plug.
• Measure the glow plug resistance with a multimeter. Compare it to the reference value for your engine (usually less than 1 ohm; check exact data in BMW technical documentation).
• If resistance deviates significantly (open or short), replace the glow plug.

Step 3: Check Wiring and Connector

• Inspect the wire harness to the plug for damage, chafing, corrosion, or loose contacts.
• Check insulation integrity and that the connector is securely seated.
• Repair the wiring or replace damaged sections as needed.

Step 4: Check the Glow Plug Control Module

If code P0672 persists after replacing the plug and checking the wiring, or if faults on several plugs appear at once, check the Glow Plug Control Module. Testing the module requires specialized equipment and can be done with ISTA. If a fault is confirmed, replace the module.

Common Diagnostic Mistakes

• Replacing the plug without checking the wiring and connector may not fix the problem if the harness is damaged.
• Ignoring related codes on other cylinders can lead to misdiagnosing the control module.

Repair

• Replace the faulty cylinder 2 glow plug (part number selected by VIN and engine model).
• Repair the circuit if the wiring is damaged.
• Replace the Glow Plug Control Module if it is faulty.

Secondary Issues

Long-term operation with a faulty cylinder 2 glow plug can lead to the following:

• Hard cold starts and increased wear on the starter motor and battery from extended cranking.
• Rough running when cold, which promotes carbon buildup on valves and in the combustion chamber.
• Higher emissions and possible clogging of the diesel particulate filter (DPF) from incomplete combustion.
• Risk of damage to the Glow Plug Control Module if a short occurs in the plug circuit.

Fix the fault as soon as possible, especially before the cold season, to avoid startup complications and extra stress on components.