DTC P0621 L61
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.
Conditions for Setting the DTC
DTC P0621 will set if generator L-terminal output voltage at the PCM is less
than 4 volts when:
| • | The condition exists for longer than 15 seconds. |
OR
Generator L-terminal output voltage at the PCM is greater than 4 volts
when:
| • | The condition exists for longer than 5 seconds. |
| • | The engine is NOT running. |
DTC P0621 diagnostic runs continuously with the ignition ON.
DTC P0621 is a type D DTC.
Diagnostic Aids
With the ignition ON and the engine OFF, voltage measured with a DVOM on circuit 225
at the generator with the connector disconnected should read 5 volts.
A generator that is not charging with the engine running will pull circuit 225,
through resistance, to ground and set this DTC.
An intermittent open or short to ground on circuit 225 will set this
DTC. GENERATOR F-TERMINAL DC on the scan tool will read 0 percent with the
ignition ON if this occurs.
GENERATOR F-TERMINAL DC on the scan tool should read near 17 percent
with the ignition ON and the engine OFF.
DTC P0621 L81
Circuit Description
The L-terminal circuit 225 is the link between the ECM and the generator.
The ECM supplies the generator with 12 volts whenever the ignition is On. Once
the engine is running, the generator must have the 12 volt supply to charge.
If the engine is NOT running or the generator stops charging while the engine is running,
it will gorund this 12 volt supply from the ECM. When the ECM detects this
low voltage state, it will send a message to the BCM over the CAN link, which will
send a message to the I/P cluster over the Class II link to illuminate the Charge
telltale. DTC P0621 will set if the voltage at the generator L-terminal input is high
when the engine is NOT running.
Conditions for Setting the DTC
| • | DTC P0621 will set if generator L-terminal input voltage at the
ECM is greater than 4.0 volts when: |
| - | Condition exists for longer than 3 seconds |
| • | DTC P0621 diagnostic runs continuously with ignition On and engine
Off. |
| • | P0621 is a (type D) DTC. |
Diagnostic Aids
| • | With ignition On, engine Off, voltage measured with a DVOM on circuit 225
at the generator with the ring terminal disconnected should read battery voltage.
With the ring terminal connected, voltage whould be between 1.0-1.6 volts. |
| • | An intermittent open or short to voltage on circuit 225 will set
this DTC. |
| • | To locate an intermittent problem, use Scan tool to monitor the IGNITION 1
voltage. Wiggling the wires with the engine running may locate the area where an open
in circuit 225 exists. If this occurs, the generator will stop charging. |
DTC B3538
