The L-terminal circuit 225 is a 2-way link between the PCM and generator. The PCM supplies the generator with 5 volts whenever the ignition is ON. The PCM will not supply 5 volts to the generator during engine cranking if battery voltage is below 9.6 volts. Once the engine is running, the generator must have the 5 volt supply to charge. If the generator stops charging while the engine is running, it will ground this 5 volt supply from the PCM. When the PCM detects this ground, it will send a message to the I/P cluster over the Class II link to illuminate the charge telltale. The PCM determines electrical system load by monitoring the generator pulse width modulated (PWM) output on the F-terminal circuit 23.
Conditions for Setting the DTC
DTC P0622 will set if generator F-terminal duty cycle is less than 5 percent when:
| • | The condition exists for longer than 30 seconds. |
| • | The engine speed is between idle and 3,000 RPM. |
OR
DTC P0622 will set if generator F-terminal duty cycle is greater than 65 percent when:
| • | The condition exists for longer than 5 seconds. |
| • | The engine is NOT running. |
DTC P0622 diagnostic runs continuously with the ignition ON.
DTC P0622 is a type D DTC.
Diagnostic Aids
If DTC P0621 is also set, diagnose that DTC first. The generator will output a 0 percent duty cycle if it does not have 5 volts at the generator L-terminal while the engine is running.
If a low circuit fault occurs in the F-terminal circuit while the engine is running, the charge telltale will illuminate, however, the generator will still charge. This only applies if the L-terminal circuit is functioning properly.
An open/short to ground or short to voltage on circuit 23 will set this DTC.
GENERATOR F-TERMINAL DC on the scan tool should read near 17 percent with the ignition ON and the engine OFF.
