P0621

Diagnostic Chart:

Schematic:

CIRCUIT DESCRIPTION
The PCM uses the L-terminal circuit to control the toad of the generator on the engine. A high side driver in the PCM applies a voltage to the voltage regulator. This signals the voltage regulator to turn the field circuit ON and OFF. When the PCM turns ON the high side driver, the voltage regulator turns ON the field circuit. When the PCM turns OFF the high side driver, the voltage regulator turns OFF the field circuit.

The PCM monitors the state of the L-terminal circuit. The PCM should detect a low L-terminal voltage when the key is ON and the engine is OFF, or when the charging system malfunctions. With the engine running, the PCM should detect a high L-terminal voltage. The PCM performs key ON and RUN tests to determine the status of the L-terminal circuit. During the key ON test, if the PCM detects a high L-terminal voltage, DTC P0621 will set. DTC P0621 will also set if, during the RUN test, the PCM detects a low L-terminal voltage. When the DTC sets, the PCM will send a class 2 serial data message to illuminate the charging telltale.

CONDITIONS FOR RUNNING THE DTC

Key ON Test
^ No generator, CKP sensors, or CMP sensor DTCs are set.
^ The key is in the RUN position.
^ The engine is not running.

Run Test
^ No generator, CKP sensors, or CMP sensor DTCs are set.
^ The engine is running.

CONDITIONS FOR SETTING THE DTC
^ During the key ON test, the PCM detects a high signal voltage on the L-terminal circuit for at least 5 seconds.
OR
^ During the RUN test, the PCM detects a low signal voltage on the L-terminal circuit for at least 15 seconds.

ACTION TAKEN WHEN THE DTC SETS
^ The PCM will not illuminate the Malfunction Indicator Lamp (MIL).
^ The PCM will store the conditions present when the DTC set as Fail Records data only.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.
^ The DTC can be cleared by using the scan tool Clear DTC Information function.

DIAGNOSTIC AIDS
If the condition is intermittent, refer to Intermittent Conditions in Symptoms. Intermittent Conditions