DTC P0622 Diesel
Circuit Description
The engine control module (ECM)/powertrain control module (PCM) uses the generator field duty cycle signal circuit to monitor the duty cycle of the generator. The generator field duty cycle signal circuit connects to the high side of the field winding in the generator. A pulse width modulated (PWM) high side driver in the voltage regulator turns the field winding ON and OFF. The ECM/PCM uses the PWM signal input to determine the generator load on the engine. This allows the ECM/PCM to adjust the idle speed to compensate for high electrical loads.
The ECM/PCM monitors the state of the generator field duty cycle signal circuit. When the key is in the RUN position and the engine is OFF, the ECM/PCM should detect a duty cycle near 0 percent. However, when the engine is running, the duty cycle should be between 5 percent and 100 percent. The ECM/PCM monitors the PWM signal using a key ON test and a RUN test. During the tests, if the ECM/PCM detects an out of range PWM signal, DTC P0622 will set. When the DTC sets, the ECM/PCM will send a class 2 serial data message to the instrument panel cluster (IPC) to illuminate the charge indicator.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0622 Generator F-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 less than 3,000 RPM. |
Conditions for Setting the DTC
| • | During the ignition ON test, the ECM/PCM detects a PWM signal is between 10-40 percent for more than 6 seconds. |
| • | During the RUN test, the ECM/PCM detects a PWM signal less then 5 percent for more than 6 seconds. |
Action Taken When the DTC Sets
| • | The ECM/PCM will store the conditions present when the DTC set as Fail Records data only. |
| • | 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/PCM receives the clear code command from the scan tool. |
Diagnostic Aids
On vehicles equipped with a sense circuit connected to the voltage regulator. This circuit must have voltage for the charging system to operate properly. This circuit is used as a reference to control system voltage. All circuits must be tested at the generator before replacing any components. refer to system schematic to confirm if the vehicle being serviced uses the sense circuit as part of the charging system.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Starting and Charging Schematics Connector End View Reference: Engine Electrical Connector End Views | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |
2 |
Does the scan tool indicate that DTC P0622 has passed? | Go to Testing for Intermittent Conditions and Poor Connections | Go to Step 3 |
3 | Test the F-terminal signal circuit for a short to voltage, short to ground or an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 6 | Go to Step 4 |
4 | Inspect for poor connections at the harness connector of generator. Refer to Connector Repairs . Did you find and correct the condition? | Go to Step 6 | Go to Step 5 |
5 | Replace the Generator. Refer to Generator Replacement . Did you compete the replacement? | Go to Step 6 | -- |
6 |
Does the scan tool indicate that this DTC failed this ignition? | Go to Step 2 | System OK |
