P0621
DTC P0621
Circuit Description
The 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 ECM applies a voltage to the voltage regulator. This signals the voltage regulator to turn the field circuit ON and OFF. When the ECM turns ON the high side driver, the voltage regulator turns ON the field circuit. When the ECM turns OFF the high side driver, the voltage regulator turns OFF the field circuit.
The ECM monitors the state of the generator turn on signal circuit. The 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 ECM should detect a high generator turn on signal circuit. The 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 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 ECM detects a low generator turn on signal circuit. When the DTC sets, the ECM will turn on the charge indicator in the instrument panel cluster (IPC).
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0621 Generator L-Terminal Circuit
Conditions for Running the DTC
* The ignition is ON.
* The engine speed is more than 1,000 RPM.
Conditions for Setting the DTC
* The ECM detects the GEN L-Terminal active with the ignition ON.
* The ECM detects the GEN L-Terminal inactive with the engine operating.
* The above conditions are present for 6 seconds.
Action Taken When the DTC Sets
* The ECM will record the operating conditions presents when the DTC set as Failure Records data only.
* The IPC displays a message.
* The malfunction indicator lamp (MIL) will not illuminate.
Conditions for Clearing the DTC
* The Conditions for Setting the DTC are no longer present.
* A history DTC will clear after 40 malfunction-free ignition cycles.
* The ECM receives the clear code command from the scan tool.
Test
