Cylinder 3 injector circuit fault.
P0203 — also written PO2O3, P 0203, 0203 — is the OBD-II code for injector circuit — cylinder 3. Same code, same fix: this page covers every spelling of it.
Injector circuit fault on cylinder 3 — one of the most common injector codes on UK diesels, particularly PSA 1.6 HDi and VW 2.0 TDI engines past 80,000 miles.
P0203 is a fuel & air fault code, typically costing £120–£600 to put right in a UK garage.
What P0203 actually feels like to drive
- Engine drops into limp mode at motorway speeds, then resets after a restart
- Slight knock or 'diesel knock' specifically when cold
- Loss of power above 2,500 RPM only
- Slightly elevated fuel consumption (1–3 MPG drop)
- Code returns within 100 miles of clearing
What causes P0203?
- Failed injector
- Wiring
UK vehicles that throw P0203 most often
- Peugeot 308/3008/Partner 1.6 HDi (2010–2018)
- Citroën Berlingo / C4 1.6 HDi
- Ford Focus/Mondeo 1.6 TDCi (shared PSA engine)
- Volvo V40/V60 D2/D3 (PSA-derived diesel)
- Mini Cooper D 1.6 (PSA engine)
- Volkswagen Golf/Passat 2.0 TDI CR — injector wiring loom failure
How P0203 is fixed
- Injector replacement
The P0203 misdiagnosis that wastes money
We routinely see cars in the workshop where someone has already swapped the cylinder 3 injector based on the code alone — when the actual fault was a corroded pin on the injector connector, a chafed wire in the loom near the EGR cooler, or a failing fuel pressure regulator dropping rail pressure on all four cylinders. Always test the circuit before condemning a £200–£400 injector.
What a UK garage should charge for P0203
UK independent garage: diagnostic £50–£80, injector loom repair £90–£160, single injector replacement £280–£520 fitted (including coding to the ECU), full set £900–£1,400. Main dealer: typically 40–60% more for the same parts and labour.
P0203 repair cost in the UK
Most P0203 repairs land between £120–£600 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 P0203
Before authorising any injector replacement, ask the garage to read live injector correction values on a scan tool with diesel manufacturer-level coverage. If cylinder 3's correction value is wildly different from the other three at idle, the injector is genuinely faulty. If all four correction values look similar but the code still returns, you've got a wiring or fuel supply issue — not an injector.
Can you drive with P0203?
Avoid driving.
Urgency: high.