P0201 Injector Circuit Malfunction (Cylinder 1) — Causes & Fix
Updated for 2026 diagnostics & repair guidance
P0201 at a Glance
What it means
The ECU has detected a fault in the fuel injector electrical circuit for cylinder 1.
Most common cause
Faulty injector, wiring damage, or ECU driver fault.
Severity
Moderate to serious — causes misfire on cylinder 1.
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 P0201 Mean?
P0201 is a generic OBD-II code indicating the Engine Control Unit (ECU) has detected an electrical fault in the fuel injector circuit for cylinder 1. This could be an open circuit, short circuit, or incorrect resistance in the injector solenoid or its wiring. The ECU may disable fuel delivery to cylinder 1, causing the engine to run on three cylinders.
Common Causes
Injector-Related Causes
Failed injector solenoid
The electromagnetic coil inside the injector has failed, preventing it from opening. This is the most common cause on vehicles over 80,000 miles.
Incorrect injector coding
If an injector was recently replaced without coding, the ECU may flag a circuit fault due to mismatched parameters.
Other Possible Causes
Damaged wiring to injector
The wiring harness between the ECU and injector is damaged, corroded, or broken. Common in vehicles exposed to salt spray or engine bay heat.
Corroded injector connector
The electrical connector on top of the injector has corroded internally, creating high resistance. Often caused by water ingress.
ECU injector driver fault
The transistor in the ECU that drives the injector has failed. Less common but requires ECU repair or replacement.
Symptoms Drivers Notice
- Engine misfires and runs rough, especially at idle
- Noticeable vibration through the steering wheel and cabin
- Loss of power during acceleration
- Engine management light illuminated (steady or flashing)
- Increased fuel consumption (10-20%)
- White or black smoke from exhaust
Vehicles Commonly Affected
Can You Still Drive with P0201?
Driving short distances at low load is generally safe. However, prolonged driving on three cylinders can cause: unburnt fuel contaminating the DPF, increased load on the catalytic converter, oil dilution from fuel washing past the piston rings, and secondary damage to the turbocharger. We recommend diagnosis within 48 hours.
How Mechanics Diagnose P0201
- 1
Read and confirm fault codes
Use an OBD scanner to confirm P0201 and check for additional codes (e.g., P0300 general misfire).
- 2
Inspect wiring and connector
Visually inspect the injector connector and wiring harness to cylinder 1 for damage, corrosion, or loose connections.
- 3
Measure injector resistance
Disconnect the injector and measure resistance across the solenoid pins. Compare to spec (typically 0.3-1.2 ohms for solenoid injectors).
- 4
Perform leak-off test
If electrical tests pass, perform a leak-off test to check for mechanical injector failure.
- 5
Swap test (optional)
Swap the cylinder 1 injector with another cylinder. If the code follows the injector, it confirms injector failure.
Repair Solutions & Costs
Replace the injector
If the injector solenoid has failed, replacement is the only fix. Remanufactured injectors are a cost-effective, OEM-spec option.
Repair the wiring
If the wiring is damaged, repair or replace the affected section. Soldering and heat-shrinking is the professional approach.
Clean or replace connector
Corroded connectors can sometimes be cleaned with electrical contact cleaner. Severely corroded connectors should be replaced.
ECU repair
If the ECU injector driver has failed, specialist ECU repair is needed. This is uncommon but possible on high-mileage vehicles.
When Injector Replacement Is Required
Injector replacement is required when: the solenoid resistance is out of spec, the leak-off test shows excessive return flow, the swap test confirms the fault follows the injector, or the injector has visible signs of damage (cracked body, burnt connector).
Compatible Injector Part Numbers
5 injectors compatible with engines affected by P0201.
Cross Reference Numbers
OEM and alternative part numbers for injectors affected by P0201.
Affected Vehicle & Engine Combinations
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
Frequently Asked Questions
Explore Related Content
- Diesel Injector Failure Symptoms: 9 Warning Signs You S...
- Diesel Engine Misfire Causes: Injector Faults & Diagnos...
- White Smoke from Diesel Engine: Causes, Injector Faults...
- Hard Starting Diesel in Cold Weather: Causes, Diagnosis...
- Car Shaking at Idle (Diesel): Injector & Engine Vibrati...
- Diesel Injector Leak-Off Test: Step-by-Step Guide for A...
- Injector Coding After Replacement: Complete Guide by Ve...
- How to Remove and Replace Diesel Injectors: Complete Wo...
Need Help With P0201?
Our diesel specialists can help diagnose the issue and find the right injector.