What does it mean?
P1245 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Needle Lift Sensor -G80- Short to ground .
Symptoms
- The MIL is on and injection timing can no longer be corrected
- Hard cold starting and rough running until the engine warms up
- Noticeably louder, knocking combustion sound
- Loss of power and poor throttle response
- Black or grey smoke and higher fuel consumption
- Start of injection value on the scan tool frozen or reading zero
Likely causes
- Signal wire chafed against the cylinder head, camshaft cover or a bracket and shorted to ground
- Water, coolant or diesel intrusion in the sensor connector on top of the injector
- Internal short in the needle lift sensor coil built into the injector that carries it
- Damaged or crushed harness section where the loom passes over the engine
- Broken shield of the sensor cable touching the signal conductor
- Poor repair joint or aftermarket splice in the sensor circuit
- Failed control module input stage, the least likely cause
How to fix it
- Check live data for the needle lift signal and the start of injection value; a signal stuck at zero supports a short to ground
- Inspect the harness from the injector connector back to the module, paying attention to points where it crosses hot or sharp metal
- Unplug the sensor and measure resistance between each signal pin and ground; a very low reading confirms the short
- Measure the sensor winding resistance across its two pins and compare with the specified value
- Dry and clean the connector, check for corroded terminals and repair the cable shield if it is damaged
- Replace the damaged harness section rather than taping over a chafed area
- If wiring and connector test good, replace the injector that carries the needle lift sensor, then relearn injection timing and road test