The ECU has not stored the crank sensor variation values it needs to detect misfires accurately. Very common after a crank sensor, ECU or engine repair.
P0315 — also written PO315, P 0315, 0315 — is the OBD-II code for crankshaft position system variation not learned. Same code, same fix: this page covers every spelling of it.
P0315 is a engine fault code, typically costing £40–£90 to put right in a UK garage.
What causes P0315?
- Crank relearn procedure never carried out after a repair
- Replaced crank sensor or flywheel
- ECU replaced or re-flashed
How P0315 is fixed
- Carry out the crankshaft variation relearn with a capable scan tool — usually a ten-minute drive procedure
- No parts normally required
P0315 repair cost in the UK
Most P0315 repairs land between £40–£90 including parts and labour. The spread is wide because the cheap fix (a sensor, a hose, a leak) and the expensive fix (a major component) throw the same code — which is why a proper diagnosis before parts are bought saves the most money.
Can you drive with P0315?
Yes. This is a procedure, not a broken part.
Urgency: low.
What P0315 is telling you
This code is the ECU saying the engine is not behaving the way its map predicts. The job in the workshop is finding which link in that chain is lying.
On P0315 specifically — crankshaft position system variation not learned — the stored code records the moment that check failed, not the moment the part gave up. That gap is why two cars with the same code can need completely different repairs.
How P0315 is diagnosed properly
Each of the known causes is ruled in or out in cost order, cheapest and most likely first. On P0315 that means working through them like this:
- Crank relearn procedure never carried out after a repair — confirmed with live data before any part is bought.
- Replaced crank sensor or flywheel — compared against live data and a known-good reference before it is condemned — a sensor reading the wrong thing accurately is a different fault from a dead one.
- ECU replaced or re-flashed — checked for outstanding manufacturer updates before any hardware is touched.
An hour of diagnostic time on P0315 routinely saves more than it costs, because the alternative is buying the most expensive part on that list and hoping.
The repairs that actually clear P0315
- Carry out the crankshaft variation relearn with a capable scan tool — usually a ten-minute drive procedure
- No parts normally required
After the repair the code is cleared and the car is driven until the relevant readiness monitor completes, rather than handed back as soon as the light goes out. A code that has only been erased will come straight back on the next drive cycle.
What happens if P0315 is ignored
This is not an emergency, but it is not a code to clear and forget either. It will return, and while it is stored the ECU is running a fallback value rather than a measured one.
For reference, P0315 typically lands at £40–£90 all-in at an independent garage in the UK — main-dealer quotes for the same job usually sit above that.
Getting P0315 looked at
Bob's Mechanical Repairs is an independent garage in Birnam, Dunkeld, Perthshire, with 32 years of Bob's experience on the tools. If P0315 is showing on your car, bring the scan results with you — we will read the live data ourselves, tell you which of the causes above it actually is, and price the repair before any work starts.