fault code guide
P0393: Camshaft Position Sensor 'B' Circuit High (Bank 2)
The engine computer is detecting an unusually high voltage signal from the exhaust camshaft sensor on cylinder bank two. Your car may start slowly, lose power, or stall, so it needs checking soon.
How it shows up: The amber engine management light will stay on steadily, and you might notice long cranking before the engine catches, sluggish acceleration, or occasional stalling. The P0393 code is identified when a diagnostic scanner is plugged into the car.
Updated 9 November 2026
Can I keep driving?
Service soon
You can usually drive short distances, but the car risks unexpected stalling at junctions or dropping into limp mode if the computer cannot track engine timing.
What to do right now
- 1Pull over safely to a car park or hard shoulder if the engine stutters severely or cuts out.
- 2Turn off the ignition, wait a minute, and restart to check if the engine starts smoothly or cranks for a long time.
- 3Drive gently at moderate speeds and avoid overtaking until you can have the car properly diagnosed.
Likely causes
Most likely first.
- Likely
Faulty camshaft position sensor
An internal electrical breakdown or short circuit inside the Bank 2 exhaust sensor causes it to send maximum voltage back to the engine computer.
- Possible
Damaged sensor wiring harness
Chafed or melted insulation can allow the sensor signal wire to contact a 5-volt reference wire or a 12-volt battery power feed, pulling the signal voltage too high.
- Possible
Corroded or wet electrical connector
Moisture or road grime entering the sensor plug can bridge the electrical terminals and create a short to power.
- Rare
Engine control unit fault
An internal failure on the engine computer circuit board can lead to incorrect voltage readings even when the sensor and wiring are sound.
What you can check yourself
Park somewhere safe and level, engine off, before you start.
- 1
Inspect the Bank 2 sensor wiring
Park on level ground, switch off the engine, and open the bonnet. Locate the exhaust camshaft sensor on cylinder bank two and check the visible wiring for signs of melting, rubbing against metal brackets, or rodent damage.
- 2
Check the sensor connector
Gently unclip the wiring plug from the sensor and inspect the pins inside. Look for green corrosion, bent metal terminals, or water ingress, as any bridging between pins can cause a circuit high fault.
- 3
Check engine oil level
Pull the dipstick, wipe it with a clean cloth, reinsert it fully, and draw it out again. Ensure the oil is within the correct markings, as severely low or contaminated oil can disrupt camshaft timing components and cause secondary sensor faults.
Rough cost to fix
Rough estimateTypical prices in Ireland (€) and the UK (£), from an independent garage up to a main dealer. The total bill mainly depends on whether the fix is a simple plug-in sensor replacement or requires tracing a broken wire deep inside the engine bay loom.
Bank 2 camshaft position sensor replacement
- Do it yourself
- €40–120£35–105 in the UK
- At a garage
- €130–280£110–240 in the UK
Sensor wiring harness repair
- Do it yourself
- Garage job
- At a garage
- €100–260£85–225 in the UK
Engine control unit (ECU) testing and repair
- Do it yourself
- Garage job
- At a garage
- €550–1,350£475–1,150 in the UK
When to go to a garage
- The engine cuts out unexpectedly while driving or refuses to restart after stopping.
- Inspecting the sensor requires removing the intake manifold or other large engine bay components.
- The engine management light returns immediately after fitting a replacement sensor or clearing the fault code.
Questions drivers ask
Can I keep driving with code P0393?
You can usually drive the car short distances to get home or visit a local garage, provided the engine runs smoothly. However, the computer cannot accurately time fuel injection and spark timing without this signal, which can lead to poor fuel economy, loss of power, or unexpected stalling at junctions.
What do Sensor B and Bank 2 mean?
Bank 2 refers to the cylinder bank on a V-type or horizontally opposed engine that does not house cylinder number one. Sensor B designates the exhaust camshaft sensor, meaning the computer has detected an electrical fault specifically on the exhaust side of that cylinder bank.
Will code P0393 cause an NCT or MOT fail?
On an MOT in the UK, an illuminated engine management light is an automatic fail for petrol cars first used from July 2003 and diesels from July 2008. On the Irish NCT, an engine management light or stored fault code results in an Advisory Pass rather than an automatic fail, unless the fault causes your exhaust emissions to exceed legal limits.
Will clearing the code fix the problem?
Clearing the code with a scanner only switches the warning light off until the engine control unit completes its next electrical self-test. Because P0393 indicates a circuit voltage fault, the computer will detect the short circuit or broken sensor almost immediately and illuminate the light again.
Test rules here are for the National Car Test in Ireland (NCT) and the MOT in the UK. Elsewhere, check the regulations of your own country or state before going for a vehicle test.
The warning light you may see
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General guidance for most cars, not a diagnosis of yours. Details differ by make, model and year - check your handbook, and if in doubt, don't drive.