P0672
PowertrainCylinder 2 Glow Plug Circuit
A glow plug is the little heater that sits in each cylinder of a diesel and warms the combustion chamber so the engine fires up cleanly when it's cold. This code says the ECU has spotted an electrical fault in the glow plug circuit for cylinder 2 specifically. With that one heater out of action, you'll mostly notice it on cold mornings: harder starting, a bit of stumble and smoke until the engine warms through and the other cylinders pick up the slack.
ⓘ Information only. This page provides general educational information about fault code P0672. We do not assess the urgency or safety implications of any specific fault. That requires in-person diagnosis by a qualified mechanic. Full terms.
Recommended next steps
Whether a fault is urgent, drivable, or routine depends entirely on the cause on a specific vehicle, and that can only be determined by a qualified mechanic with diagnostic equipment. If a warning light is illuminated, the most reliable next step is professional diagnosis.
What does P0672 mean?
P0672 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Cylinder 2 Glow Plug Circuit.
This is a standardised OBD-II code. The technical definition is the same regardless of the make or model of vehicle, although specific causes and symptoms can vary between vehicles.
Symptoms commonly associated with this code
Symptoms that drivers often report alongside this code. Not all may apply to every case:
- • Hard starting from cold, worse the colder it gets and after the car's been stood overnight
- • Engine warning light on, and on some diesels the coil-shaped glow plug light stays on or flashes
- • Rough, lumpy idle for the first minute or two from cold, smoothing out as it warms
- • Puffs of dark or white smoke from the exhaust on cold start
- • A flat, sluggish feel until the engine is up to temperature
- • Faint diesel-knock or chuffing while cylinder 2 isn't contributing properly
Possible causes
Causes commonly associated with P0672, listed in approximate order of typical investigation. The actual cause on a specific vehicle can only be confirmed by professional diagnosis.
- 1. Glow plug in cylinder 2 has gone open circuit, the single most common reason this code shows up. Plugs are a wear item and one usually dies before the rest
- 2. Corroded or loose connector on the glow plug tip. The clip-on connectors sit in a dirty, hot part of the engine and break down with age
- 3. Broken or chafed wire between the glow plug control module and that cylinder, often where the loom runs near hot exhaust parts
- 4. Faulty glow plug control module or relay not sending current to that channel
- 5. High resistance in the supply, either at a corroded busbar terminal or a poor earth, dropping the current the plug needs to heat
- 6. ECM driver fault for that circuit. Rare, but it does happen on high-milers, so rule everything else out first
How mechanics typically diagnose
A typical diagnostic sequence used by mechanics, provided here for educational reference only. Diagnostic work should be performed by a qualified mechanic with the appropriate tools and training.
- 1. Pull the connector off the cylinder 2 glow plug and measure resistance from the plug terminal to a clean earth. A healthy plug reads roughly 0.5 to 2.0 ohms. An open circuit or sky-high reading means the plug itself is dead, which is the usual answer
- 2. Eyeball the connector and the few inches of wire feeding it before you go further. Crumbly green corrosion or a connector that's gone soft and melted is a giveaway, and it's cheap to put right
- 3. Back-probe the supply wire with the ignition on and the preheat cycle running. If you see battery voltage arriving but the plug doesn't get hot, the plug's at fault. No voltage points back at the relay, control module, or a broken supply wire
- 4. Check resistance along the supply wiring from the glow plug busbar to that cylinder to catch high-resistance joints and breaks the visual check missed
- 5. Scan for other stored codes. If P0670 (the control circuit code) is sitting there too, sort that one first because it can cause all the individual cylinder codes
- 6. Clear the code, run it through a few cold-start cycles, then re-scan to confirm cylinder 2 stays quiet
Common questions about P0672
What am I looking at to get this sorted at a garage? +
If it's just the plug, an independent will usually do one for somewhere around £60 to £130 fitted, depending on how buried the engine is. Newer common-rail diesels like the VAG 2.0 TDI or the PSA/Ford 1.6 HDi/TDCi can be a fiddle to reach, which pushes labour up. A full set of four runs roughly £150 to £350 fitted. If the plug has seized and snaps, you're into specialist extraction and possibly head removal, and that can climb to four figures fast. Control module work is typically £200 to £500. Main dealers tend to be a fair bit dearer for the same job.
How do I know if it's the plug or the wiring on my car? +
Resistance test the plug first. Disconnect it and measure across the terminal to earth. If it reads open or way above about 2 ohms, the plug's gone and that's your answer for most cars. If the plug reads fine, the fault is upstream: check the connector for corrosion, then confirm whether battery voltage is actually reaching that wire during the preheat cycle. Voltage present plus a good plug that won't heat is unusual and points at the plug after all, but no voltage at the plug means you chase the relay, the control module, or a broken wire back along the loom.
Can I just swap the one glow plug myself? +
You can, and on a low-mileage engine where the plug comes out cleanly it's a sensible afternoon job with a deep socket and a multimeter. The thing that catches people out is seizing. On engines past 80,000 miles the plug's threads can be carboned in solid, and forcing a cold one will shear the body off inside the head. Get the engine warm first, soak the threads with penetrant, work it loose gently, and stop if it won't budge. If you're already paying labour and the plugs are old, do all of them while it's apart so you're not back in a month for the next one.
Information only, not professional advice
The information on this page is provided for general guidance and educational purposes only. It is not a substitute for diagnosis or repair advice from a qualified mechanic. Always verify any fault before paying for repairs. carfaultcodes.co.uk accepts no liability for decisions made based on this information. Full terms →