Possible causes – Faulty Fuel Tank Pressure Sensor– Fuel Tank Pressure Sensor harness is open or shorted– Fuel Tank Pressure Sensor circuit poor electrical connection Tech notes On most GMC vehicles the sensor is on top of the fuel tank.

Possible causes – Faulty Glow Plug Control Module (GPCM)– GPCM harness is open or shorted– GPCM circuit poor electrical connection– Faulty Engine Control Module (ECM) When is the code detected? The Engine Control Module (ECM) has detected a fault on

Possible causes – Faulty Heated Oxygen Sensor (H2OS) Bank 1 Sensor 1 circuit– Heated Oxygen Sensor (H2OS) Bank 1 Sensor 1 circuit fuse– Heated Oxygen Sensor (H2OS) Bank 1 Sensor 1 circuit open shorted to ground– Heated Oxygen Sensor (H2OS)

Possible causes – Faulty Heated Oxygen Sensor (H2OS) Bank 1 Sensor 1– Heated Oxygen Sensor (H2OS) Bank 1 Sensor 1 circuit fuse– Heated Oxygen Sensor (H2OS) Bank 1 Sensor 1 circuit open shorted to ground– Heated Oxygen Sensor (H2OS) Bank

Possible causes – Faulty Heated Oxygen Sensor (H2OS) Bank 1 Sensor 1– Heated Oxygen Sensor (H2OS) Bank 1 Sensor 1 harness is open shorted to ground– Heated Oxygen Sensor (H2OS) Bank 1 Sensor 1 circuit poor electrical connection– Heated Oxygen

Possible causes – Faulty Heated Oxygen Sensor (H2OS) Bank 1 Sensor 1– Heated Oxygen Sensor (H2OS) Bank 1 Sensor 1 harness is open shorted to ground– Heated Oxygen Sensor (H2OS) Bank 1 Sensor 1 circuit poor electrical connection– Heated Oxygen

Possible causes – Faulty Heated Oxygen Sensor (H2OS) Bank 1 Sensor 2– Heated Oxygen Sensor (H2OS) Bank 1 Sensor 2 circuit fuse– Heated Oxygen Sensor (H2OS) Bank 1 Sensor 2 circuit open shorted to ground– Heated Oxygen Sensor (H2OS) Bank

Possible causes – Faulty Heated Oxygen Sensor (H2OS) Bank 1 Sensor 2– Heated Oxygen Sensor (H2OS) Bank 1 Sensor 2 fuse– Heated Oxygen Sensor (H2OS) Bank 1 Sensor 2 harness is open or shorted– Heated Oxygen Sensor (H2OS) Bank 1

Possible causes – Faulty Heated Oxygen Sensor (H2OS) Bank 1 Sensor 2– Heated Oxygen Sensor (H2OS) Bank 1 Sensor 2 fuse– Heated Oxygen Sensor (H2OS) Bank 1 Sensor 2 harness is open or shorted– Heated Oxygen Sensor (H2OS) Bank 1

Possible causes – Faulty Heated Oxygen Sensor (H2OS) Bank 1 Sensor 2– Heated Oxygen Sensor (H2OS) Bank 1 Sensor 2 fuse– Heated Oxygen Sensor (H2OS) Bank 1 Sensor 2 harness is open or shorted– Heated Oxygen Sensor (H2OS) Bank 1

Possible causes – Faulty Heated Oxygen Sensor (H2OS) Bank 2 Sensor 1– Heated Oxygen Sensor (H2OS) Bank 2 Sensor 1 circuit fuse– Heated Oxygen Sensor (H2OS) Bank 2 Sensor 1 harness is open shorted to ground– Heated Oxygen Sensor (H2OS)

Possible causes – Faulty Heated Oxygen Sensor (H2OS) Bank 2 Sensor 1– Heated Oxygen Sensor (H2OS) Bank 2 Sensor 1 harness is open shorted– Heated Oxygen Sensor (H2OS) Bank 2 Sensor 1 circuit poor electrical connection– Heated Oxygen Sensor (H2OS)

Possible causes – Faulty Heated Oxygen Sensor (H2OS) Bank 2 Sensor 1– Heated Oxygen Sensor (H2OS) Bank 2 Sensor 1 harness is open shorted– Heated Oxygen Sensor (H2OS) Bank 2 Sensor 1 circuit poor electrical connection– Heated Oxygen Sensor (H2OS)

Possible causes – Faulty Heated Oxygen Sensor Bank 1 Sensor 1– Heated Oxygen Sensor Bank 1 Sensor 1 harness is open or shorted– Heated Oxygen Sensor Bank 1 Sensor 1 circuit poor electrical connection Symptoms – Engine Light ON (or

Possible causes – Faulty Heated Oxygen Sensor Bank 1 Sensor 2– Heated Oxygen Sensor Bank 1 Sensor 2 harness is open or shorted– Heated Oxygen Sensor Bank 1 Sensor 2 circuit poor electrical connection Symptoms – Engine Light ON (or

Possible causes – Faulty Heated Oxygen Sensor Bank 1 Sensor 3– Heated Oxygen Sensor Bank 1 Sensor 3 harness is open or shorted– Heated Oxygen Sensor Bank 1 Sensor 3 circuit poor electrical connection Tech notes Replacing the O2 Sensor

Possible causes – Faulty Ignition Coil 1– Ignition Coil 1 harness is open or shorted– Ignition Coil 1 circuit poor electrical connection– Faulty Powertrain Control Module (PCM) When is the code detected? Each ignition circuit is continuously monitored by the

Possible causes – Faulty Ignition Coil 2– Ignition Coil 2 harness is open or shorted– Ignition Coil 2 circuit poor electrical connection– Faulty Powertrain Control Module (PCM) When is the code detected? Each ignition circuit is continuously monitored by the

Possible causes – Faulty Ignition Coil 3– Ignition Coil 3 harness is open or shorted– Ignition Coil 3 circuit poor electrical connection– Faulty Powertrain Control Module (PCM) When is the code detected? Each ignition circuit is continuously monitored by the

Possible causes – Faulty Ignition Coil 4– Ignition Coil 4 harness is open or shorted– Ignition Coil 4 circuit poor electrical connection– Faulty Powertrain Control Module (PCM) When is the code detected? Each ignition circuit is continuously monitored by the