P0352
PowertrainIgnition Coil"B" Primary/Secondary Circuit
The ECU has spotted an electrical problem in the circuit feeding ignition coil 'B', which on most engines is the coil for cylinder 2. That means the spark for that cylinder isn't firing properly, so you'll usually feel a misfire and the engine light will be on. For the owner it's normally a straightforward job: a coil, a plug, or the wiring that connects them.
ⓘ Information only. This page provides general educational information about fault code P0352. 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 P0352 mean?
P0352 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Ignition Coil"B" Primary/Secondary 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:
- • Engine warning light on, sometimes flashing if the misfire is bad enough to threaten the cat
- • Rough, lumpy idle with the car feeling like it's shuddering at a standstill
- • Flat spot or hesitation when you put your foot down, worst under load going up a hill or pulling away
- • A distinct misfire on cylinder 2 that feels like a stumble or kick
- • Worse fuel economy, and on a cold morning it can be reluctant to start
- • Whiff of unburnt petrol from the back of the car
Possible causes
Causes commonly associated with P0352, listed in approximate order of typical investigation. The actual cause on a specific vehicle can only be confirmed by professional diagnosis.
- 1. The coil on cylinder 2 has failed, by far the most common cause. Heat cycles, age and oil seeping down the plug well all kill coils over time
- 2. Damaged or corroded connector at the coil, or a pin that's worked loose. Very common on engines where the connector clip has gone brittle
- 3. Worn or fouled spark plug on cylinder 2 making the coil work harder than it should, which then trips the circuit fault
- 4. Cracked or perished coil boot letting moisture in or letting the spark arc to earth, often shows up after washing the engine or in heavy rain
- 5. Open circuit, short to earth or high resistance somewhere in the harness between the ECU and the coil
- 6. A failed coil-driver transistor inside the ECU, rare, but it does happen and will read as an open circuit even with perfect wiring
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 all stored codes and look at what's keeping it company. A P0302 alongside the P0352 confirms cylinder 2 is the one actually misfiring, which lines up with the coil 'B' diagnosis
- 2. Get the connector off and have a proper look. Check for green corrosion on the pins, a cracked plastic clip, oil in the plug well, and a coil boot that's split or hardened. A surprising number of these are sorted right here
- 3. Swap the cylinder 2 coil with the one from cylinder 1 or 3 and clear the codes. If the fault follows the coil to its new cylinder, you've found it. If it stays on cylinder 2, the problem is in the plug, wiring or ECU
- 4. Pull the plug on cylinder 2 and inspect it. Heavy wear, a cracked porcelain or oily fouling means it goes in the bin
- 5. Check the coil with a multimeter against the maker's figures. Primary is usually around 0.5 to 2.0 ohms and secondary roughly 8,000 to 15,000 ohms, though check your engine's spec. Readings well outside that point to a dead coil
- 6. If the coil and plug check out, test the harness for continuity, voltage feed and a clean earth back to the ECU
Common questions about P0352
If I just clear the code, will it stay gone? +
Only if the underlying fault was a one-off, which it rarely is. A failed coil or split boot will set the code again within a few miles, sometimes before you've left the drive. The one time clearing helps is after you've actually fixed it, because the misfire counter needs resetting and the light won't go out on its own straight away. Clearing without repairing just hides the problem until the ECU notices again.
What's the worst that happens if I leave it? +
A persistent misfire dumps raw fuel into the exhaust, and that fuel burns inside the catalytic converter instead of the cylinder. Over time it cooks the cat, and a cat is a far dearer fix than a coil. You're also running on three cylinders worth of power, so you'll feel it labouring and drinking fuel. If the light is flashing, the misfire is bad enough to be doing damage right now.
How quickly do I need to sort it? +
Days, not weeks. A solid warning light with a mild misfire will get you to the garage without drama, so book it in soon and don't keep flogging it on long motorway runs. A flashing light is a different matter. Ease off the throttle, keep the revs low and get it looked at as a priority, because that's the engine telling you it's actively harming the cat.
Is it the coil itself or just the wiring? +
Most of the time it's the coil, especially on higher-mileage engines where they tend to fail one at a time. But corroded connectors and brittle clips catch plenty of people out, so a five-minute look at the plug and connector is worth doing before you spend money. The coil-swap test settles it: if the fault moves with the coil, buy a coil. If it stays put on cylinder 2, the cause is in the plug, the harness or the ECU driver. Many mechanics fit a fresh plug at the same time as the coil if it's anywhere near due.
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 →