Ford P0203

Injector circuit malfunction Cylinder 3 on Ford — usually a failed injector or chafed wiring loom on TDCi/EcoBoost engines.

Ford P0203 — Injector circuit malfunction Cylinder 3 on Ford — usually a failed injector or chafed wiring loom on TDCi/EcoBoost engines. Typical UK independent garage cost: £180–£580.

What actually causes P0203 on a Ford

On Ford 2.0/2.2 TDCi (Mondeo and Transit) the injector loom chafes against the engine cover from vibration — common across all 4 cylinders but cyl 3 sits at the back where the loom flexes most. On 1.0 EcoBoost cyl 3 is the rearmost cylinder and the injector itself fails by 80k miles; smell of petrol from the back of the engine bay is the giveaway. Often paired with a rough idle and slight loss of power.

Ford engines that log P0203

• 1.6/2.0/2.2 TDCi (Mondeo, Transit, Focus, Galaxy)
• 1.0 EcoBoost (Fiesta, Focus, B-Max)
• 1.5/1.6 EcoBoost (Focus ST, Mondeo)

How we diagnose P0203 on a Ford

1. Visually inspect the cyl 3 injector loom for chafing against the camshaft cover or rocker box
2. Measure injector resistance (typically 0.5–2 Ω depending on type) and compare to other cylinders
3. Swap injector connector with cyl 1 or 2 — if the code follows the wiring, it's the loom; if it stays at cyl 3, it's the injector
4. On 1.0 EcoBoost, smell-test for petrol at the back of the engine bay
5. Read injector trim/correction values via FORScan

The common misdiagnosis to avoid

Garages routinely replace the injector before testing the wiring — on TDCi vans, the chafed loom causes the exact same code for £15 of harness repair instead of £180–£280 per injector.

Ford P0203 repair cost in the UK

Expect £180–£580 including parts and labour at an independent garage. Main-dealer quotes on Ford are usually higher for the same job, and the spread exists because the cheap cause and the expensive cause throw the same code — pay for the diagnosis before you pay for parts.

Bob's workshop tip

On 2.2 TDCi Transits with chafed looms, fit the Ford-updated injector wiring harness (about £45) and route it properly — saves a return visit when the next cylinder logs the same fault 6 months later.

Codes usually seen alongside P0203 on Ford

• P0201
• P0202
• P0204
• P0300

Symptoms drivers report with P0203

• 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

Repairs that clear P0203

• Injector replacement

For the generic, all-makes explanation of this code — meaning, every known cause and UK cost bands — see our P0203 guide.