Field wire to alternator open or shorted.
P0622 — also written PO622, P 0622, 0622 — is the OBD-II code for generator field terminal circuit. Same code, same fix: this page covers every spelling of it.
This code means the ECU has lost its 'handshake' with the alternator's field circuit, common on Ford 'Smart Charge' systems and Vauxhalls where the wiring loom has rubbed through.
P0622 is a electrical fault code, typically costing £150–£700 to put right in a UK garage.
What P0622 actually feels like to drive
- Battery light flickering or staying on solid after a cold start.
- The 'Smart Charge' system defaults to 13.8V, so the car runs but the battery never feels fully 'crisp'.
- Headlights slightly pulsing or flickering at idle.
- Auto Stop-Start stops working entirely (the car knows the charging isn't 100%).
- A 'Check Charging System' message on the dash, often intermittent.
What causes P0622?
- Broken field wire
- Failed alternator
UK vehicles that throw P0622 most often
- Ford Transit 2.2 TDCi (2006-2014) - Loom rub-through near the starter.
- Ford Focus 1.6/2.0 TDCi (2005-2011) - Corroded 3-pin alternator plug.
- Vauxhall Insignia 2.0 CDTi (A20DTH) - Alternator clutch pulley or regulator failure.
- BMW 3 Series (E90/F30) - LIN-bus communication errors.
- Mini Cooper 1.6 (R56) - Oil wicking into the alternator harness from the solenoid.
How P0622 is fixed
- Repair wiring
- Replace alternator
The P0622 misdiagnosis that wastes money
I see folk throwing brand-new alternators at this P0622 all the time, only to find the battery light stays on. On the Ford Transit and Focus models, the real culprit is usually the three-pin plug on the back of the alternator. The wiring harness rubs against the engine or the gearbox casing and snaps the tiny 'sense' wire internally. You can't see the break because the insulation looks fine, but the wire inside is toast. They swap the unit, spend £250, and still have the same code. Always tug-test those thin wires before condemning the metalwork.
What a UK garage should charge for P0622
A basic diagnostic plug-in is £50–£80 in a local shop. If it’s just the wiring pigtail that needs replacing, you're looking at £120–£150. However, if the regulator inside the unit has fried, a quality reconditioned Bosch or Denso alternator will set you back £250–£400 plus two hours of labour at £60–£100 per hour. Don't buy the £80 eBay specials; they rarely communicate with the UK spec ECUs and the light will stay on. Total bill usually lands between £180 and £600.
P0622 repair cost in the UK
Most P0622 repairs land between £150–£700 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.
Bob's tip on P0622
If a garage tells you the alternator is 'dead' based on this code, ask them if they've performed a 'continuity test' on the LIN-bus or signal wire back to the PCM. A genuine Bosch or Denso alternator for a modern diesel is pricey, so you want to be sure it's not just a £5 wiring repair. Also, insist they check the 'smart charging' system fuses—on many Peugeots and Fords, a blown 10A fuse in the engine bay box will trigger this P0622 and stop the battery from charging properly, even if the alternator is perfect.
Can you drive with P0622?
Yes short-term.
Urgency: medium.