P0203 Injector Circuit Malfunction (Cylinder 3) — Causes & Fix
Updated for 2026 diagnostics & repair guidance
P0203 at a Glance
What it means
The ECU has detected a fault in the fuel injector electrical circuit for cylinder 3.
Most common cause
Faulty injector, wiring damage, or ECU driver fault.
Severity
Moderate to serious — causes misfire on cylinder 3.
Can you drive?
Short distances only. Prolonged driving risks DPF and catalytic converter damage.
Typical repair cost
£100-£350 for injector replacement; £40-£100 for wiring repair.
What Does P0203 Mean?
P0203 indicates the ECU has detected an electrical fault in the fuel injector circuit for cylinder 3. Cylinder 3 is the third from the timing belt end on inline engines. The diagnostic and repair approach is the same as P0201/P0202.
Common Causes
Injector-Related Causes
Failed injector solenoid
The cylinder 3 injector solenoid has failed electrically.
Other Possible Causes
Damaged wiring to injector
Wiring harness damage to cylinder 3 injector.
Corroded injector connector
Connector corrosion on cylinder 3 injector.
ECU injector driver fault
Cylinder 3 driver transistor failure in ECU.
Symptoms Drivers Notice
- Engine misfires and runs rough at idle
- Vibration through steering wheel and cabin
- Loss of power during acceleration
- Engine management light on
- Increased fuel consumption
- Exhaust smoke (white or black)
Vehicles Commonly Affected
Can You Still Drive with P0203?
Short distances at low load are safe. Diagnose within 48 hours to prevent DPF contamination and oil dilution.
How Mechanics Diagnose P0203
- 1
Read and confirm fault codes
Confirm P0203 targets cylinder 3.
- 2
Inspect wiring and connector
Check cylinder 3 injector wiring for damage.
- 3
Measure injector resistance
Test solenoid resistance (spec: 0.3-1.2 ohms).
- 4
Perform leak-off test
Check all injectors for mechanical wear.
- 5
Swap test
Swap cylinder 3 injector to confirm fault source.
Repair Solutions & Costs
Replace the injector
Remanufactured injector replacement.
Repair the wiring
Repair damaged wiring.
Clean or replace connector
Clean or replace corroded connector.
Replacing injectors? Browse our remanufactured diesel injectors, reconditioned injectors or refurbished diesel injectors — all bench-tested with a 12-month warranty.
When Injector Replacement Is Required
Replace when solenoid resistance is out of spec, leak-off confirms excessive return, or swap test proves fault follows injector.
Compatible Remanufactured Injectors
OEM bench-tested injectors for engines affected by P0203 — verified pricing, 12-month warranty, free UK delivery.
Siemens VDO / Continental A2C9303500080
2.0L EcoBlue Remanufactured Common Rail Injector (Ford Transit / Transit Custom / Tourneo Custom)
Fits: ADBC, ADBD, ADBE, BC2X
View injector
Siemens VDO / Continental 5WS40156Z
DW10 / 2.0 HDi / 2.0 TDCi / D4204T Remanufactured Common Rail Injector
Fits: AZWA, AZWC, D4204T, D4204T2
View injector
Bosch 0445110369
VW/Audi 2.0 TDI (EA189/EA288) Remanufactured Common Rail Injector
Fits: CDLC, CFFA, CFFB, CFFD
View injector
Delphi 28388960
Remanufactured Delphi 28388960 diesel injector for Ford 2.0 TDCi and Peugeot/Citroen 2.0 HDi/BlueHDi DW10 engines. Direct replacement for Ford Mondeo, Kuga, S-Max, Galaxy, Focus, C-Max, Edge and Peugeot 308, 508, 3008, 5008, Expert, Citroen C4, C5, DS4, DS5, Jumpy, Jumper applications. Cross-references 28602948, 9674984080, DS7Q9F593BA, HRD360. OEM-tested and calibrated with full flow and leak-back verification. Includes 12-month unlimited-mileage warranty. Supplied as an exchange unit — return your old injector within 30 days.
Fits: AZBA, AZBC, DW10C, DW10CB
View injector
Siemens VDO / Continental A2C59511606
Siemens VDO / Continental A2C59511606 remanufactured diesel injector for Renault, Nissan and Dacia 1.5 dCi K9K engines. OEM tested and calibrated on CR318 PRO test bench. 12-month warranty included. Free UK delivery. Exchange unit — return your old injector within 30 days.
Fits: K9K278, K9K282, K9K288, K9K292
View injector
Bosch 0445110955
PSA/Ford 1.5 EcoBlue/BlueHDi Remanufactured Common Rail Injector
Fits: BEGA, D15DT, D15DTH, YHR
View injector
Bosch 0445110351
1.3L Multijet/JTD/TDCi/HDi/DDiS Remanufactured Common Rail Injector
Fits: 1.3JDTM, 1.3JTD, 1.3SDE, 169A1.000
View injector
Bosch 0445110470
VW/Audi 2.0 TDI (EA288 Gen2) Remanufactured Common Rail Injector
Fits: CNHA, CNHC, CRGB, CUNA
View injectorCompatible Injector Part Numbers
11 injectors compatible with engines affected by P0203.
3294238468
Bosch · from £90.00
5WS40156-Z
Siemens VDO / Continental · from £90.00
0987654567
Bosch · from £99.88
765C591356
Bosch · from £100.00
0867673265
Bosch · from £100.00
56445647
Bosch · from £100.00
32475294386
Bosch · from £100.00
8923423466
Siemens · from £100.00
100054325
Bosch · from £100.00
664378392
Siemens · from £100.00
32896792
Bosch · from £100.00
Cross Reference Numbers
OEM and alternative part numbers for injectors affected by P0203.
Affected Vehicle & Engine Combinations
Trusted Injector Families for These Engines
Verified remanufactured injector families fitted to engines documented to log P0203.
A2C9303500080
Siemens VDO / Continental · 2.0L EcoBlue
Engines: ADBC, ADBD, ADBE, BC2X, BCCC, BCCD
5WS40156Z
Siemens VDO / Continental · DW10 / 2.0 HDi / 2.0 TDCi / D4204T
Engines: AZWA, AZWC, D4204T, D4204T2, D4204T5, DW10BTED4
0445110369
Bosch · VW/Audi 2.0 TDI (EA189/EA288)
Engines: CDLC, CFFA, CFFB, CFFD, CFFE, CFGB
28388960
Delphi · 2.0L HDi
Engines: AZBA, AZBC, DW10C, DW10CB, DW10CT, DW10CTED4
A2C59511606
Siemens VDO / Continental · 1.5L dCi
Engines: K9K278, K9K282, K9K288, K9K292, K9K430, K9K728
0445110955
Bosch · PSA/Ford 1.5 EcoBlue/BlueHDi
Engines: BEGA, D15DT, D15DTH, YHR, YHV, YHW
Need a Replacement Injector?
UK-tested remanufactured injectors with 12-month warranty. Search by engine code or vehicle registration.
Need it fast? Same-day dispatch on in-stock injectors.
Order before 2pm for next working day delivery (UK mainland). Call us on 020 3355 6581.
Engine-Specific Guides
Mercedes OM651
Injector guide
BMW N47
Injector guide
BMW B47
Injector guide
Ford Transit 2.2 TDCi
Injector guide
PSA DW10C
Injector guide
VW CAYC
Injector guide
Mercedes OM646
Injector guide
Renault 1.5 dCi K9K
Injector guide
Renault / Nissan M9R
Injector guide
Ford 2.0 TDCi TXDB
Injector guide
JLR 3.0 TDV6 306DT
Injector guide
BMW M47
Injector guide
Frequently Asked Questions
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Fault Codes
Why It Happens
Common-rail injectors live at extreme pressures with clearances measured in microns. Fuel quality, heat cycles and mileage wear the internal control valve and nozzle: back-leak rises, spray patterns deteriorate and delivery drifts from calibration. Most 'engine' complaints on high-mileage diesels trace back to this gradual injector wear.
Professional Diagnosis
Workshops follow a fixed order: scan for codes and freeze-frame data, compare requested vs actual rail pressure on live data, read cylinder balance corrections, then run a comparative leak-off test. That sequence identifies the faulty injector without guesswork — and prevents needlessly replacing pumps, sensors or the wrong injector.
Typical Workshop Findings
The most frequent findings are: one injector returning several times the leak-off volume of its neighbours; carbon build-up from a failed copper washer; corroded injector connectors; and missing injector coding after a previous repair. Genuine high-pressure pump failures are rarer than back-leak faults that mimic them.
When to Replace Injectors
Replace when testing proves internal wear: leak-off clearly above the other injectors, balance corrections at their limits, or a failed bench test. Cleaning and additives cannot restore worn internal clearances. Bench-tested remanufactured injectors restore original calibration at a fraction of the new price — always coded to the ECU where the engine requires it.
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