Possible causes – Faulty spark plug 5– Clogged or faulty fuel injector 5– Faulty ignition coil 5– Fuel injector 5 harness is open or shorted– Fuel injector 5 circuit poor electrical connection– Ignition coil 5 harness is open or shorted–

Possible causes – Faulty spark plug 6– Clogged or faulty fuel injector 6– Faulty ignition coil 6– Fuel injector 6 harness is open or shorted– Fuel injector 6 circuit poor electrical connection– Ignition coil 6 harness is open or shorted–

Possible causes – Faulty spark plug 7– Clogged or faulty fuel injector 7– Faulty ignition coil 7– Fuel injector 7 harness is open or shorted– Fuel injector 7 circuit poor electrical connection– Ignition coil 7 harness is open or shorted–

Possible causes – Faulty spark plug 8– Clogged or faulty fuel injector 8– Faulty ignition coil 8– Fuel injector 8 harness is open or shorted– Fuel injector 8 circuit poor electrical connection– Ignition coil 8 harness is open or shorted–

Possible causes – Faulty Throttle Position Sensor– Throttle Position Sensor circuit is open or shorted– Throttle Position Sensor poor electrical connection When is the code detected? Malfunction is detected when an excessively low or high voltage from the sensor is

Possible causes – Faulty throttle position sensor– Throttle position sensor harness is open or shorted– Throttle position sensor circuit poor electrical connection When is the code detected? An excessively high voltage from the Throttle Position (TP) Sensor is sent to

Possible causes – Faulty throttle position sensor– Throttle position sensor harness is open or shorted– Throttle position sensor circuit poor electrical connection When is the code detected? An excessively low voltage from the Throttle Position (TP) Sensor is sent to

Possible causes – Faulty Transmission Fluid Temperature Sensor– Transmission Fluid Temperature Sensor harness is open or shorted– Transmission Fluid Temperature Sensor circuit poor electrical connection When is the code detected? Transmission Control Module (TCM) detects excessively high voltage from the

Possible causes – Faulty Transmission Fluid Temperature Sensor– Transmission Fluid Temperature Sensor harness is open or shorted– Transmission Fluid Temperature Sensor circuit poor electrical connection When is the code detected? Transmission Control Module (TCM) detects excessively low or high voltage

Possible causes – Faulty Transmission Fluid Temperature Sensor– Transmission Fluid Temperature Sensor harness is open or shorted– Transmission Fluid Temperature Sensor circuit poor electrical connection When is the code detected? Transmission Control Module (TCM) detects excessively low voltage from the

Possible causes – Faulty Vacuum hoses damaged– Faulty Air Pump inoperative– Air bypass solenoid harness is open or shorted– Air bypass solenoid circuit poor electrical connection– Air bypass solenoid leaking/blocked or stuck open/closed– Air diverter valve leaking/blocked or stuck open/closed

Possible causes – Faulty Vehicle Speed Sensor– Vehicle Speed Sensor harness is open or shorted– Vehicle Speed Sensor circuit poor electrical connection When is the code detected? If the fault detection circuit senses a voltage other than what is expected,

Possible causes – Faulty Vehicle Speed Sensor– Vehicle speed sensor harness or connectors is open or shorted– Vehicle speed sensor circuit poor electrical connection– Faulty Powertrain Control Module (PCM) When is the code detected? If the Powertrain Control Module (PCM)

Possible causes – Faulty Vehicle Speed Sensor– Vehicle speed sensor harness or connectors is open or shorted– Vehicle speed sensor circuit poor electrical connection– Faulty Powertrain Control Module (PCM) When is the code detected? The almost 0 km/h (0 MPH)

Possible causes – Faulty Vehicle Speed Sensor– Vehicle speed sensor harness or connectors is open or shorted– Vehicle speed sensor circuit poor electrical connection– Faulty Powertrain Control Module (PCM) When is the code detected? When the Powertrain Control Module (PCM)

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

Possible causes – Intake air heater relay Tech notes The most common problem that sets code p0540 is the air intake relay Symptoms – Engine Light ON (or Service Engine Soon Warning Light) P0540 GMC Description The Engine Control Module

Possible causes – Intake air leaks– Faulty front heated oxygen sensor– Ignition misfiring – Faulty fuel injectors – Exhaust gas leaks– Incorrect fuel pressure– Lack of fuel– Faulty Mass Air Flow (MAF) sensor– Incorrect Positive Crankcase Ventilation (PCV) hose connection

Possible causes – Intake air leaks– Faulty front heated oxygen sensor– Ignition misfiring– Faulty fuel injectors– Exhaust gas leaks– Incorrect fuel pressure– Lack of fuel– Faulty Mass Air Flow (MAF) sensor– Incorrect Positive Crankcase Ventilation (PCV) hose connection Tech notes

Possible causes – Leaking or stuck open thermostat– Low engine coolant level– Insufficient warm up time– Faulty engine coolant temperature sensor– Engine coolant temperature sensor harness is open or shorted– Engine coolant temperature sensor circuit poor electrical connection Tech notes