P1266

What it means

P1266 on a Ford means the engine control system has detected a short between the high side and low side of the cylinder 6 fuel injector circuit. The control unit, or the injector driver module on engines that have one, saw an electrical fault in that circuit when it checked the injector drive. The exact circuit layout and which unit sets the code depend on the engine, so check the model-specific wiring information.

Symptoms

• Engine misfire or rough running, especially at idle
• Hard starting or long cranking
• Loss of power or poor acceleration
• Cylinder 6 not firing, or an uneven, knocking idle
• Engine warning light on, possibly with increased fuel consumption or smoke
• Engine stalling or cutting out intermittently

Possible causes

• Damaged, chafed or shorted wiring between the control unit and the cylinder 6 injectorlikely
• Faulty cylinder 6 injector with an internal short in the coil or solenoidlikely
• Corroded, wet or damaged connector or injector harness pins at cylinder 6 (including the valve cover pass-through connector where fitted)likely
• Oil or coolant contamination of the harness or connector, causing leakage between circuitspossible
• Fault in the injector driver module or control unit output stagepossible
• Poor power or earth supply to the injector driver circuit, such as a weak battery or bad connectionrare

How to diagnose

1. Read all stored and pending codes and the freeze frame data, and note any other injector or misfire codes
2. Check the battery condition and charging voltage, as low voltage can cause false injector circuit faults
3. Visually inspect the cylinder 6 injector connector and the harness for chafing, heat damage, oil contamination and corrosion
4. Check the engine harness routing near cylinder 6 for rubbing against brackets, the head or the manifold
5. With the circuit isolated and the ignition off, measure the resistance of the cylinder 6 injector against the specification for that engine
6. Test the injector circuit wiring for shorts between the high and low side wires and to earth, using the wiring diagram for the exact model
7. Compare cylinder 6 with the other injectors, for example by swapping the injector or its connections if the engine allows it, to see whether the fault follows
8. If the injector and wiring test good, check the driver module or control unit supply and earths before suspecting the unit itself

How to fix

• Repair or replace the damaged section of wiring, and secure it so it cannot rub again
• Replace the cylinder 6 injector if it has an internal short or its resistance is out of specification
• Clean or replace corroded or contaminated connectors and terminals, and renew any leaking seals that let oil in
• Replace the injector harness or pass-through connector if it is internally damaged or oil-soaked
• Replace the injector driver module or control unit only after the wiring and injector are proven good, and follow the correct programming procedure
• Repair poor battery, power or earth connections found during testing, then clear the code and road test to confirm

Can I keep driving?

This code for other makes

• P1266LincolnCylinder 6 High To Low Side Short
• P1266MercuryCylinder 6 High To Low Side Short
• P1266OtherCylinder #6 High To Low Side Short

Nearby codes

• P1265FordCylinder #5 High To Low Side Short
• P1267FordCylinder #7 High To Low Side Short