Pinpoint Test C: DTC P0620
Pinpoint Test
Pinpoint Test C: DTC P0620
Normal Operation
The PCM monitors the generator output via the generator monitor (GENMON) circuit. The PCM uses the generator command (GENCOM) circuit to command the generator to either increase or decrease output. If the GENCOM circuit (generator control circuit) or the "A" sense circuit are open or shorted to ground, the PCM will not be able to control the generator output. When the engine speed is greater than approximately 2,000 rpm, the generator defaults to a steady voltage output of approximately 13.5 volts and the PCM sends a message over the High Speed Controller Area Network (HS-CAN) to the Instrument Panel Cluster (IPC) through the Body Control Module (BCM) to illuminate the charging system warning indicator lamp.
- DTC P0620 (Generator Control Circuit)- The PCM sets this DTC if the GENCOM circuit or "A" sense circuit is open or shorted to voltage or ground.
This pinpoint test is intended to diagnose the following:
- Fusible link
- Wiring, terminals or connectors
- Generator
- PCM
PINPOINT TEST C : DTC P0620
NOTE: Make sure battery voltage is greater than 12.2 volts prior to and during this pinpoint test.
NOTE: Do not have a battery charger attached during vehicle testing.
C1 CHECK THE BATTERY CONDITION
- Carry out the Battery- Condition Test to determine if the battery can hold a charge and is OK for use. Pinpoint Tests
Does the battery pass the condition test?
Yes
GO to C2.
No
INSTALL a new battery. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
C2 CHECK THE GENERATOR B+ CONNECTION
- Ignition OFF.
- Disconnect: Generator C102A (gas) or C1104A (diesel).
- Inspect generator C102B, circuit SDC14 (RD) (gas) or C1104B, circuit SDC14 (RD) (diesel). Connector should be installed correctly and tight. Inspect the connector for bent and/or pushed out pins.
- Measure the voltage between generator B+ C102B, circuit SDC14 (RD) (gas) or C1104B, circuit SDC14 (RD) (diesel) and ground.
Are the generator connections OK and does the generator B+ measure battery voltage?
Yes
GO to C3.
No
REPAIR the generator connection or circuit. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
C3 CHECK THE VOLTAGE DROP IN THE B+ CIRCUIT
- Ignition OFF.
- Connect: Generator C102A (gas) or C1104A (diesel).
- Start the engine.
- With the engine running at idle, headlamps ON and the heater blower set to HIGH, measure the voltage drop between generator B+ C102B, circuit SDC14 (RD) (gas) or C1104B, circuit SDC14 (RD) (diesel) and the positive battery terminal.
Is the voltage drop less than 0.5 volt?
Yes
GO to C4.
No
REPAIR the circuit B+ SDC14 (RD) and the positive battery cable for loose connections, physical damage or wire corrosion. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
C4 "A" SENSE CIRCUIT LOAD TEST
NOTICE: The following step uses a test light to simulate normal circuit loads. Use only the test light recommended in the Special Tools table at the beginning. To avoid connector terminal damage, use the Flex Probe Kit for the test light probe connection to the vehicle. Do not use the test light probe directly on any connector.
NOTE: This step puts a load on the "A" sense circuit. If there are corroded or loose connections, loading the circuit may help show the fault. A 250-350 mA incandescent 12-volt test lamp is required for this step. This circuit will not be loaded properly using an LED-style test lamp.
- Disconnect: Generator C102A (gas) or C1104A (diesel).
- Using a 12-volt test lamp connected to ground, check for voltage at generator C102A-3, circuit SDC14 (RD) (gas) or C1104A-3, circuit SDC14 (RD) (diesel), harness side.
Does the test lamp illuminate?
Yes
GO to C5.
No
VERIFY the fusible link is OK. If OK, REPAIR circuit SDC14 (RD). If not OK, REFER to the Wiring Diagrams to identify the possible causes of the circuit short. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation. [1][2]Diagrams By Number
C5 CHECK THE GENERATOR COMMAND LINE FAULT (GENCMD_LF) PID
- Start and idle the engine.
- NOTE: Many of the PCM PIDs selected will be monitored later in this pinpoint test.
With the engine still running at idle, select and monitor the following PCM PIDs:
- Generator Monitor (GENMON).
- Generator Command (GENCMD).
- Generator Command Line Fault (GENCMD_LF).
Does the GENMON_LF PID display a fault?
Yes
GO to C6.
No
GO to C9.
C6 CHECK THE GENCOM CIRCUIT FOR A SHORT TO POWER
- Ignition OFF.
- Disconnect: Generator C102A (gas) or C1104A (diesel).
- Ignition ON.
- Measure the voltage between generator C102A-2, circuit CDC10 (BU/OG) (gas) or C1104A-2, circuit CDC09 (YE) (diesel), harness side and ground.
Does voltage read 1 volt or less?
Yes
GO to C7.
No
GO to C11.
C7 COMPARE THE PCM PIDs GENERATOR MONITOR (GENMON) AND GENERATOR COMMAND (GENCMD)
- Ignition OFF.
- Connect a fused jumper wire between:
- For gasoline engines, generator C102A-1, circuit CDC15 (VT), harness side and generator C102A-2, circuit CDC10 (BU/OG), harness side.
- For diesel engines, generator C1104A-1, circuit CDC15 (VT), harness side and generator C1104A-2, circuit CDC09 (YE), harness side.
- Start the engine.
- Monitor the GENMON and GENCMD PIDs while performing a Wiggle Test on the generator harness.
Does the GENMON PID read within 2% of the GENCMD PID?
Yes
GO to C8.
No
GO to C12.
C8 CHECK THE GENERATOR COMMAND CIRCUIT FOR DAMAGE OR AN OPEN
- Ignition OFF.
- Disconnect: PCM C175B or PCM C1232B.
- Inspect the following harness connectors for damaged or pushed-out pins:
- PCM C175B-53, circuit CDC10 (BU/OG) (gas) or C1232B-53, circuit CDC09 (YE) (diesel).
- Generator C102A-2, circuit CDC10 (BU/OG) (gas) or C1104A-2, circuit CDC09 (YE) (diesel).
- For gasoline engines, measure the resistance between PCM C175B-53, circuit CDC10 (BU/OG), harness side and generator C102A-2, circuit CDC10 (BU/OG), harness side.
For diesel engines, measure the resistance between PCM C1232B-53, circuit CDC09 (YE), harness side and generator C1104A-2, circuit CDC09 (YE), harness side.
Are the connectors and pins free of damage and is the resistance less than 5 ohms?
Yes
GO to C9.
No
REPAIR circuit CDC09 (YE) or CDC10 (BU/OG). CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
C9 CHECK THE GENERATOR COMMAND CIRCUIT FOR A SHORT TO GROUND
- Ignition OFF.
- Disconnect: Generator C102A (gas) or C1104A (diesel) (if not previously disconnected).
- Measure the resistance between the generator C102A-2, circuit CDC10 (BU/OG) (gas) or C1104A-2, circuit CDC09 (YE) (diesel), harness side and ground.
Is the resistance greater than 10,000 ohms?
Yes
GO to C10.
No
REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
C10 CHECK THE CHARGING SYSTEM CIRCUITS FOR INTERMITTENT FAULTS
- Connect: Generator C102A (gas) or C1104A (diesel).
- Connect: PCM C175B (gas) or C1232B (diesel).
- Ignition ON.
- Clear all DTCs.
- Start the engine and let the engine run for 5 minutes.
- Retrieve Continuous Memory Diagnostic Trouble Codes (CMDTCs) from all modules.
Did any charging system DTC get stored into memory?
Yes
INSTALL a new generator. REFER to Generator - Gasoline Engines , Generator - 6.7L Diesel, Single Generator or Generator - 6.7L Diesel, Dual Generator . CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
No
The fault is not present at this time. This may indicate an intermittent fault. CARRY OUT a wiggle test on the charging system circuits to try and recreate the concern. CHECK generator connections for corrosion, loose connections and/or bent terminals. REPAIR as necessary. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
C11 CHECK FOR SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: PCM C175B (gas) or C1232B (diesel).
- Ignition ON.
- Measure the voltage between generator C102A-2, circuit CDC10 (BU/OG) (gas) or C1104A-2, circuit CDC09 (YE) (diesel), harness side and ground.
Is any voltage present?
Yes
INSTALL a new PCM. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
No
REPAIR circuit CDC09 (YE) or CDC10 (BU/OG). CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
C12 INSPECT GENERATOR CIRCUITS
- Ignition OFF.
- Disconnect: PCM C175B (gas) or C1232B (diesel).
- For gasoline engines, inspect the following connector pins for damage and/or corrosion:
- PCM C175E-50, circuit GD113 (BK/YE)
- generator C102A-1, circuit CDC15 (VT)
- generator C102A-2, circuit CDC10 (BU/OG)
- For diesel engines, inspect the following connector pins for damage and/or corrosion:
- PCM C1232B-2, circuit GD113 (BK/YE)
- generator C1104A-1, circuit CDC15 (VT)
- generator C1104A-2, circuit CDC09 (YE)
Are the connectors OK?
Yes
INSTALL a new PCM. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
No
REPAIR high resistance or loose connections in the affected circuit(s). CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.