Circuit/System Testing
- Inspect for any contamination, water intrusion or debris on the sensing elements of the MAF sensor.
- If debris is present, clean the sensor. If the sensor cannot be cleaned, replace the sensor.
- Inspect the fuse in the ignition 1 voltage circuit of the MAF sensor.
- If the fuse is open, test the ignition 1 voltage circuit for a short to ground.
- Turn OFF the ignition. Disconnect the MAF/intake air temperature (IAT) sensor. Start the engine.
- Observe the MAF/IAT sensor with a scan tool for 0 Hz.
- If more than 0 Hz, turn OFF the ignition and inspect the harness for improper routing that is too close to any aftermarket accessories, secondary ignition wires, coils, solenoids, relays or motors.
- Turn ON the ignition, with the engine OFF.
- Measure the battery voltage with a DMM.
- Disconnect the MAF/IAT sensor.
- Connect a test lamp between the ignition 1 voltage circuit of the MAF sensor and a good ground.
- Connect the DMM to the probe of the test lamp and good ground and measure for battery voltage.
- If not within 0.5 volt of battery voltage, repair the high resistance or open in the MAF sensor ignition 1 voltage circuit.
- Turn OFF the ignition and all accessories for 60 seconds to allow the control module to power down.
- Measure for 5 ohms of resistance from the ground circuit of the MAF sensor to a good ground with a DMM.
- If the resistance is more than 5 ohms, repair the high resistance or the open in the MAF sensor ground circuit.
- Turn ON the ignition, with the engine OFF.
- Measure for 4.8-5.2 volts from the signal circuit of the MAF sensor to a good ground with a DMM.
- If more than 5.2 volts, test the circuit for a short to voltage or faulty control module.
- If less than 4.8 volts, test the circuit for an open, short to ground or a faulty control module.
- Turn OFF the ignition and connect the J 38522 to the signal circuit of the MAF sensor and a good ground. See Special Tools .
- Set up the variable speed generator. Use the switches to set the duty cycle to normal, the frequency to 5 K and the signal switch to 5 volts.
- Start the engine and observe the MAF sensor parameter for 4,950-5,025 Hz with a scan tool.
- If the MAF sensor is not within the specified parameter range, test for intermittent or poor connection at the control module. If tests OK, replace the control module.
- If the MAF sensor is within the specified parameter range, test for intermittent or poor connection at the MAF sensor. If tests OK, replace the MAF sensor.