Component Testing

To determine if the ECM can properly process the MAF sensor frequency signal, connect the J 38522  to the vehicle as follows:

1. Turn OFF the ignition.
2. Connect the battery voltage supply and ground the black lead.
3. Connect the red lead to the signal circuit terminal A of the MAF sensor.
4. Set the duty cycle switch to Normal.
5. Set the Frequency switch to 5 K.
6. Set the signal switch to 5 volts.
7. Start the engine, observe the MAF Sensor parameter for the correct range of 4,950-5,025 Hz.
   • If the MAF Sensor parameter is not within the specified range, replace the ECM.
   • If the MAF Sensor parameter is within the specified range, replace the MAF sensor.