What does it mean?
P1264 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Cylinder 4 High To Low Side Short .
Symptoms
- The MIL is on and may flash during heavy misfire
- Distinct misfire on cylinder 4, worst at idle and light load
- Vibration through the steering wheel and gear lever at idle
- Reduced power and hesitation when pulling away
- Fuel smell and increased consumption
- Fault can appear intermittently as the engine reaches operating temperature
Likely causes
- Chafed insulation letting the feed and driver wires of cylinder 4 touch
- Injector winding on cylinder 4 shorted internally, often only when hot
- Contaminated connector with oil or moisture bridging the injector pins
- Loom trapped or crushed near the cylinder head during earlier repairs
- Corroded or stretched terminals no longer gripping the injector pins
- Poorly insulated repair joint in the cylinder 4 circuit
- Module output driver damaged after running with the short present
How to fix it
- Verify with the scan tool that the misfire counts belong to cylinder 4
- Disconnect the cylinder 4 injector and check the connector for moisture, oil and damaged terminals
- Measure the injector resistance and compare it with the remaining injectors
- Test the two circuit wires for a short to each other and for insulation to ground with both ends free
- Wiggle the loom around the injector while monitoring resistance to catch an intermittent short
- Move the suspect injector to another cylinder to see whether the fault follows the part
- Repair the damaged harness section or replace the cylinder 4 injector, then confirm smooth idle and no returning misfire counts