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 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.