Powertrain Chart 4, Mil Inoperative
PCM controls Malfunction Indicator Light (MIL) through circuit No. 419. Light is on when PCM has detected a problem that will affect vehicle emissions or may cause powertrain damage or driveability problems.
MIL will glow when certain PCM trouble code(s) are present or when system is in diagnostic mode.
MIL light will not glow when ignition is on and engine is not running or when engine is running and no PCM code are current. Some codes are stored without activating MIL light.
NOTE:
Test numbers refer to numbers on diagnostic chart.
- Checks 3rd digit of PD16 to determine is PCM is receiving correct input voltage. If MIL is illuminated, PCM expects to see zero volts in terminal 3F5. If it is, the 3rd digit of PD16 will be zero. If it sees greater than zero volts, the 3rd digit will be "1".
- This test checks if correct voltage is being received at PCM and if it is processed correctly.
- Checks for an open in circuit No. 419.
- Checks for voltage to high side of MIL bulb.