P0621
DTC P0621
CIRCUIT DESCRIPTION
The powertrain control module (PCM)/engine control module (ECM) uses the generator turn on signal circuit to control the load of the generator on the engine. A high side driver in the PCM/ECM applies a voltage to the voltage regulator. This signals the voltage regulator to turn the field circuit ON and OFF. When the PCM/ECM turns ON the high side driver, the voltage regulator turns ON the field circuit. When the PCM/ECM turns OFF the high side driver, the voltage regulator turns OFF the field circuit.
The PCM/ECM monitors the state of the generator turn on signal circuit. The PCM/ECM should detect a low generator turn on signal circuit voltage when the key is ON and the engine is OFF, or when the charging system malfunctions. With the engine running, the PCM/ECM should detect a high generator turn on signal circuit. The PCM/ECM performs key ON and RUN tests to determine the status of the generator turn on signal circuit. During the key ON test, if the PCM/ECM detects a high generator turn on signal circuit voltage, DTC P0621 will set. DTC P0621 will also set if, during the RUN test, the PCM/ECM detects a low generator turn on signal circuit. When the DTC sets, the PCM/ECM will send a serial data message to the instrument panel cluster (IPC) to illuminate the charge indicator.
DTC DESCRIPTOR
This diagnostic procedure supports the following DTC:
DTC P0621 Generator L-Terminal Circuit
CONDITIONS FOR RUNNING THE DTC
Key ON Test
- No generator, crankshaft position (CKP) sensors, or camshaft position (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/ECM detects a high signal voltage on the generator turn on signal circuit for at least 5 seconds.
- During the RUN test, the PCM/ECM detects a low signal voltage on the generator turn on signal circuit for at least 15 seconds.
ACTION TAKEN WHEN THE DTC SETS
- The PCM/ECM will not illuminate the malfunction indicator lamp (MIL).
- The PCM/ECM 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 DTC P0621 is intermittent on the V6 engine, the B+ cable from the generator might be getting voltage induced from the spark plug wires. Shielding the B+ cable around the area of the ignition module with nickel tape might correct the intermittent condition.
TEST
