P0672 — Cylinder 2 Glow Plug Circuit/Open

OBD-II trouble code P0672 indicates an issue with the electrical circuit of the glow plug for cylinder 2. When this code appears, it means that the Vehicle’s Engine Control Unit (ECU) has detected an abnormality—such as an open circuit—in the glow plug circuit associated with cylinder 2. This problem can affect the engine’s starting or operation, especially in cold weather. Note that the specific labeling of this DTC (Diagnostic Trouble Code) can vary between manufacturers, often reflecting their internal coding conventions.

System affected: Exhaust and Intake System / Engine Control System
Severity: Moderate
Main symptoms: Hard starting, rough idling, possible misfire
Driveability: Yes (though could be limited in cold conditions)

Manufacturer variations for trouble code P0672

Automakers may assign different labels or codes for similar issues. The underlying problem—failure in the glow plug circuit for cylinder 2—is consistent, but the diagnostic label can differ depending on the vehicle’s manufacturer. Here are some known variations:

Volkswagen / Audi: P0672 or related codes referencing « Glow plug cylinder 2 »
Ford: Usually P0672, but sometimes labeled as « Glow Plug Circuit – Cylinder 2 open »
Mercedes-Benz: Similar codes like 11-00 or 52-00 related to glow plug circuit faults, depending on model
Renault, Peugeot, Citroën: May use manufacturer-specific codes, but P0672 is common for this fault

What does trouble code P0672 mean?

The ECU monitors the operational status of each glow plug circuit to ensure proper pre-heating of the combustion chambers during cold starts. For diesel engines, glow plugs are essential components that heat the air in the cylinders, facilitating ignition and stable running in low temperatures. When the ECU detects an open circuit or malfunction in the glow plug circuit for cylinder 2, it triggers the P0672 code.

This code is generally set when the ECU registers a circuit resistance outside of specified limits or detects an interruption in the electrical circuit—examples include damaged wiring, blown fuses, or faulty glow plugs themselves. It typically appears during a functional check, cold starts, or when the engine’s management system tests the glow plug relays and circuits.

Severity and risks of trouble code P0672

The severity of P0672 is usually classified as moderate. If ignored, it may lead to some operational issues, especially during cold starts, potentially resulting in prolonged cranking times or poor engine performance. In diesel engines, ineffective glow plug operation can cause starting difficulties or increase emissions due to incomplete combustion. However, this code does not generally cause immediate engine damage and often allows the vehicle to operate normally once warmed up.

In most cases, the vehicle can still be driven, but if the glow plug circuit fault persists, there may be increased fuel consumption, rough idling, or misfire risks during cold start-up conditions. For safety and reliability, it is advisable to address the fault promptly.

Symptoms of trouble code P0672

Customers or drivers might not notice overt symptoms, but common signs include:

Hard starting in cold weather — engine may cranking longer than usual or fail to start immediately
Rough idle or misfires — especially shortly after cold start
Increased emissions — due to incomplete combustion
Glow plug warning light or check engine light illuminated on the dashboard
Poor engine performance during initial warm-up phase

Most likely causes of trouble code P0672

To troubleshoot P0672 effectively, understanding the root causes is critical. Listing from most to least common, these include:

Faulty glow plug for cylinder 2: The glow plug itself may be defective, internally shorted or open, preventing proper circuit completion.
Damaged or corroded wiring: The wiring harness connected to the glow plug or relay may be frayed, melted, or corroded, causing open circuits.
Blown fuse or relay malfunction: The fuse or relay responsible for energizing the glow plug circuit could be faulty, interrupting power supply.
ECU or sensor malfunction: In rare cases, the engine control module or associated sensors might misread or incorrectly monitor the glow plug circuit.
Incorrect wiring or aftermarket modifications: Any non-standard wiring or updates can lead to electrical faults.

How to diagnose trouble code P0672

Diagnosing P0672 requires a systematic approach, focusing on verifying circuit integrity and component functionality. The following steps outline a typical diagnostic procedure:

Visual inspection: Check for obvious damage, corrosion, or loose connectors at the glow plug wiring harness and relay contacts.
Check fuse and relay: Verify the integrity of the fuse associated with the glow plug circuit and test the relay operation if accessible.
Test glow plug resistance: Remove the glow plug for cylinder 2 and measure its resistance using a multimeter. Compare readings against manufacturer specifications.
Inspect wiring continuity: Perform continuity tests on the wiring circuit from the glow plug to the ECU or relay socket to ensure no breaks or shorts.
Use live data: Connect a scanner capable of monitoring the glow plug circuit status in real-time to see if the ECU attempts to activate the glow plug during cold starts.
Check for additional codes: Ensure no other related or pending codes may influence the diagnosis.

Possible repairs for trouble code P0672

Following diagnosis, repairs typically aim at addressing the identified cause. Possible repairs include:

Replace faulty glow plug: This is a basic repair, suitable for DIY or professional mechanics if the glow plug is confirmed defective.
Repair or replace wiring harness: Damaged wiring should be repaired or replaced by a qualified technician, especially if corrosion or melting is observed.
Replace blown fuse or faulty relay: Fuses or relays should be replaced with OEM parts to ensure proper operation.
ECU reprogramming or inspection: In rare cases, software updates or inspections might be necessary if the ECU incorrectly interprets the circuit status.

Vehicles commonly associated with trouble code P0672 in Europe

Most diesel-powered vehicles in Europe utilize glow plugs for cold starts, particularly those with direct injection engines. Common brands include:

Volkswagen Group: Audi, Volkswagen, Skoda, Seat, generally on TDI engines

Ford: Ford diesel vehicles such as the Transit, Focus, and Fiesta with diesel engines

Mercedes-Benz: Common in many diesel models, especially those with CDI engines

Renault, Peugeot, Citroën: Various models equipped with diesel engines that rely on glow plugs for cold starts

Frequent mistakes with trouble code P0672

Diagnosing and repairing P0672 can sometimes be hampered by common mistakes. Being aware of these pitfalls helps prevent misdiagnosis and unnecessary repairs:

Assuming the glow plug is faulty without testing: Always verify resistance and wiring before replacement.
Neglecting wiring integrity: Damaged wiring is often overlooked but can cause false readings.
Ignoring related sensors or relays: A faulty relay might simulate a glow plug issue without actual damage to the plug or wiring.
Overlooking other codes: Additional codes may provide clues or influence diagnosis if not checked.

FAQ — trouble code P0672

Can this code disappear on its own? Yes, sometimes temporary issues like loose connections or short circuits may resolve themselves, but persistent faults generally won’t fix spontaneously and require correction.

Can I keep driving? In most cases, yes—though cold start performance may be affected, and the glow plug warning light could stay on. However, continuous driving with unresolved glow plug faults can lead to starting difficulties.

Why does the code return after clearing it? Because the underlying cause—such as a faulty glow plug, wiring issue, or relay—is still present or not repaired, the code will reappear once the ECU performs its self-test routines during vehicle startup.