Engine Light ON (or Service Engine Soon Warning Light)
P042E GMC Possible Causes
Exhaust Gas Recirculation (EGR) Valve,EGR valve harness is open or shorted,EGR valve circuit poor electrical connection,EGR temperature sensor and circuit
P042E GMC Description
The Engine Control Module (ECM) tests the Exhaust Gas Recirculation (EGR) system during deceleration. The ECM does this by momentarily commanding the EGR valve to open while monitoring the signal circuit of the manifold absolute pressure (MAP) sensor. When the EGR valve is opened, the ECM will expect to see a predetermined increase in MAP. If the expected increase in MAP is not detected, the ECM records the amount of MAP difference that was detected and adjusts a calibrated fail counter towards a calibrated fail threshold level. The number of EGR flow test counts required to exceed the fail threshold may vary according to the amount of detected EGR flow error. The EGR valve position sensor is monitored by the ECM. The 5-volt reference circuit, the low reference circuit, and the EGR valve position signal circuit are used by the ECM to determine the EGR valve position. The ECM compares the EGR Position Sensor parameter with the desired EGR Position parameter when the valve is commanded open or closed. The ECM controls the EGR valve with a solid state device called a driver. The driver supplies the EGR solenoid with 12 volts that is pulse width modulated (PWM) through the EGR solenoid high control circuit. A ground path is provided by the ECM through the EGR solenoid low control circuit. When the ignition switch is turned ON, the ECM records the EGR Learned Minimum Position. The ECM compares the EGR Learned Minimum Position parameter to the EGR Position Sensor parameter.
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