Diagnostic Aids

DTCs that may cause a no-start should be diagnosed first:

• "U" type communications DTCs (U1000, U1016, U1064, U2105 or U2107).
• BCM or ECM PassLock® security system DTCs (P1629, P1630, P1631, P1672, B1382, B2947, B2948, B2957, B2958 or B2960).
• ECM internal fault DTCs.
• Fuel pump coil circuit DTCs (P0628 or P0629).
• Crankshaft Position (CKP) sensor circuit DTCs (P0335, P0337 or P0338).

If no CKP sensor signal is detected during engine crank when a valid camshaft sensor signal is received, DTC P0335 will set after a certain period of time. Fuel and spark will not be enabled.

If a MAF circuit fault occurs, the ECM will use engine speed and TP angle to calculate engine airflow. The engine will start if this condition occurs.

Turn ignition on, with engine off. Using scan tool, ensure ECT and MAF sensor voltage readings are normal. MAF sensor voltage should be 0.8-1.2 volts and ECT should be 4°F (2°C) of each other if vehicle has been sitting overnight. A skewed sensor reading may cause a hard or no-start condition.

Check for a flooded engine. To clear a flooded engine, depress accelerator pedal 100% while cranking engine. This engine is not equipped with a clear flood mode that cuts fuel off during engine crank, when flooded.

Ensure main relay is operating correctly. Listen for clicking sound when ignition is turned on. Relay is located in underhood fuse/relay block. Monitor main relay voltage on scan tool. Check the following fuses in the underhood fuse/relay block. These fuses will cause a no-start, if open:

• ECM/TCM (10A)
• PWR TRAIN (10A)
• FUEL PUMP (10A)
• IGN/MAN (10A)
• ECM/CAM (15A)
• ENG/IGN (15A)
• IGNITION (30A)
• BATT (40A)

Check the following fuses in the instrument panel fuse/relay block. These fuses will cause a no-start, if open:

• BCM/IGN (10A)
• BCM/CLUSTER (10A)