What does it mean?
P1266 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Cylinder 6 High To Low Side Short .
Symptoms
- The MIL is on, sometimes flashing when the misfire is severe
- Misfire on cylinder 6 with vibration felt through the body at idle
- Loss of power and jerky acceleration
- Higher fuel consumption and a fuel smell from the tailpipe
- Engine may smooth out at higher rpm but stumble again at idle
- Risk of catalytic converter damage if driven for a long period
Likely causes
- Chafed insulation letting the cylinder 6 feed and driver wires touch
- Internally shorted injector winding on cylinder 6, sometimes only when hot
- Moisture or oil in the injector connector creating a conductive path
- Loom crushed under the intake manifold or trapped by a bracket during earlier work
- Corroded terminals with a low resistance leakage path between the two pins
- Poor repair splice in the cylinder 6 circuit
- Module output driver damaged by the short, checked after the wiring is fixed
How to fix it
- Confirm on live data that only cylinder 6 is accumulating misfire counts
- Inspect and unplug the cylinder 6 injector connector, checking for oil, water and burnt terminals
- Measure the injector winding resistance and compare it with the rest of the injectors
- Test the feed and driver wires for a short to each other and for insulation to ground with both ends free
- Wiggle the loom near the injector while measuring, to catch an intermittent short
- Move the injector to a different cylinder and see whether the fault moves with it
- Repair the harness or replace the cylinder 6 injector, then verify a smooth idle and no returning misfire counts