P1264
Cylinder 4 High To Low Side Short.
- Lincoln
- Powertrain
- Manufacturer code
- Medium severity
How this code is built
- P
- SystemPowertrain
- 1
- Defined byThe manufacturer
- 2
- AreaFuel and air metering (injector circuit)
- 64
- FaultThe specific fault in that area
What it means
P1264 on a Lincoln means the powertrain control module has detected a short between the high side and low side of the cylinder 4 fuel injector circuit. The module monitors the injector driver and its circuit, and it set the code because the voltage or current did not match what it expected when it commanded that injector. The exact circuit layout and test values depend on the model and engine, so check the manufacturer data for your vehicle.
Symptoms
- Engine misfire or rough running, mainly on cylinder 4
- Engine management light on
- Noticeably reduced power or hesitation
- Rough idle or shaking at standstill
- Poor fuel economy
- Hard starting or stalling in some cases
Possible causes
- Faulty cylinder 4 fuel injector with an internal winding shortlikely
- Damaged, chafed or pinched injector wiring causing a short between the high side and low side circuitslikely
- Corroded, bent or contaminated terminals in the injector connector or wiring harness connectorpossible
- Water ingress or heat damage in the engine harness near cylinder 4possible
- Faulty injector driver within the powertrain control modulerare
- Outdated or faulty powertrain control module calibration, where a manufacturer bulletin lists it for this enginerare
How to diagnose
- Read all stored and pending codes and freeze frame data, noting engine load, temperature and speed when the fault set, and look for other injector or misfire codes.
- Visually inspect the cylinder 4 injector connector and the surrounding harness for chafing, melting, oil contamination, corrosion or pushed-back terminals.
- Check for a cylinder 4 misfire using live data and note whether it is constant or intermittent.
- With the ignition off and the injector unplugged, measure the injector winding resistance and compare it with the manufacturer specification for the engine.
- Check the injector wiring for shorts between the high and low side wires, and to ground or supply, with the module connector disconnected as the wiring diagram directs.
- Swap the cylinder 4 injector with a known good one, if the manufacturer procedure allows, to see whether the fault follows the injector.
- Using the wiring diagram, check the injector power supply and the control signal during cranking, using a suitable test lamp or oscilloscope.
- If wiring and injector are sound, check for relevant software updates and consider module fault diagnosis.
How to fix
- Replace the cylinder 4 injector if its resistance or operation is out of specification, following the correct fitting procedure and seals.
- Repair or replace the damaged section of wiring, and secure the harness away from heat and sharp edges.
- Clean or replace corroded or damaged connector terminals and the injector connector.
- Replace the damaged harness section if water or heat damage is widespread.
- Update the module calibration only where the manufacturer lists it as the fix for this fault, or repair or replace the module if the driver circuit is proven faulty.
Can I keep driving?
The car may be driven carefully for a short time, but a shorted injector circuit can cause misfires and damage to the catalytic converter or the module driver, so get it fixed soon. Avoid heavy loads and long journeys if the engine is misfiring.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.