PRE-RELEASE
DTC P0621
| DTC P0621 |
| Diagnostic Instructions |
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Perform the
Diagnostic System Check - Vehicle
prior to using this diagnostic procedure.
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Review
Strategy Based Diagnosis
for an overview of the diagnostic approach.
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Diagnostic Procedure Instructions
provides an overview of each diagnostic category.
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| DTC Descriptor |
DTC P0621
Generator L-Terminal Circuit
| Diagnostic Fault Information |
| Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
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B+
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P0625
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P0621
|
-
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-
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Control
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P0621
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P0621
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P0621
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-
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Signal
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P0625
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P0625
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P0626
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P0625
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| Circuit/System Description |
The engine control module (ECM) uses the generator turn ON control 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 controls the voltage regulator to turn the field circuit ON and OFF. The ECM monitors the state of the generator turn ON control circuit. The ECM should detect low voltage on generator turn on control circuit when the ignition is ON and the engine is OFF, or when the charging system malfunctions. With the engine running, the ECM should detect high voltage on the generator turn on control circuit.
| Conditions for Running the DTC |
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The ignition ON, engine OFF for ignition on test.
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The engine is running for the run test.
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| Conditions for Setting the DTC |
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During the ignition on test, the ECM detects voltage on the generator turn on control circuit for 5 s.
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During the run test, the ECM detects low voltage on the generator turn on control circuit for 15 s.
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| Action Taken When the DTC Sets |
DTC P0621 is a C type DTC.
| Conditions for Clearing the DTC |
DTC P0621 is a C type DTC.
| Reference Information |
Schematic Reference
Starting and Charging Schematics
Connector End View Reference
Component Connector End Views
Description and Operation
Charging System Description and Operation
Electrical Information Reference
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Circuit Testing
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Connector Repairs
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Testing for Intermittent Conditions and Poor Connections
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Wiring Repairs
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DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
| Circuit/System Testing |
| 1. |
Verify that a test lamp illuminates between the G13 Generator B+ terminal 1 X1 and ground.
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| 2. |
If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
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| 3. |
Ignition OFF, disconnect the X1 harness connector at the G13 Generator.
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| 4. |
Ignition ON, test for less than 1 V between the control circuit terminal 1 and ground.
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| 5. |
If greater than the specified range, test the control circuit for a short to voltage. If the circuit tests normal, replace the K20 Engine Control Module.
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| 6. |
Engine running, test for greater than 3.5 V between the control circuit terminal 1 and ground.
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| 7. |
If less than the specified range, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module.
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| 8. |
If the circuit tests normal, replace the G13 Generator.
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| Repair Instructions |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
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Refer to
Generator Replacement (Diesel)
Generator Replacement (LAU/A28NER)
Generator Replacement (LLU/A16LET)
Generator Replacement (LHU/A20NFT)
.
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Control Module References
for ECM replacement, setup, and programming
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