Pinpoint Test C: DTC P0620 - Generator Control Circuit
Pinpoint Test
Pinpoint Test C: DTC P0620 - Generator Control Circuit
Refer to Wiring Diagram Set 12, Charging System for schematic and connector information. Diagrams By Number
Normal Operation
The PCM monitors the generator output via the GENMON circuit. The PCM uses the 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 be unable to control the generators output. When the engine rises above approximately 2,000 rpm, the generator will default to a steady voltage of approximately 13.5 volts and the PCM will send a request to the Instrument Cluster (IC) to illuminate the charging system warning indicator lamp.
- DTC P0620 Generator Control Circuit - If the GENCOM circuit or A sense circuit are open or shorted to ground the PCM will set this DTC.
This pinpoint test is intended to diagnose the following:
- Fuse
- Wiring, terminals or connectors
- Generator
- PCM
PINPOINT TEST C: DTC P0620 - GENERATOR CONTROL CIRCUIT
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.
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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. Refer to Battery. 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.
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C2 CHECK THE GENERATOR B+ CONNECTION
- Ignition OFF.
- Inspect generator C1104A connection. Connector should be installed correctly and tight. Inspect the connector for bent and/or pushed-out pins.
- Inspect generator C1104B, circuit SDC02 (RD). Connection should be tight.
- Measure the voltage between generator C1104B, B+ circuit SDC02 (RD) 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.
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C3 CHECK THE VOLTAGE DROP IN THE B+ CIRCUIT SDC02 (RD)
- Ignition OFF.
- Connect: Generator C1104A.
- Start the engine.
- With the engine running at idle, headlamps on and blower on high, measure the voltage drop between generator B+ C1104B, circuit SDC02 (RD) and the positive battery terminal.
- Is the voltage drop less than 0.5 volt?
Yes
GO to C4.
No
REPAIR the circuit B+ SDC02 (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.
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C4 A SENSE CIRCUIT LOAD TEST
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 glass bulb style test lamp is required for this step. This circuit will not be loaded properly using an LED-style test lamp.
- Disconnect: Generator C1104A.
- Ignition ON.
- Using a 12-volt test lamp connected to ground, check for voltage at generator C1104A-3, circuit SDC02 (RD) harness side.
- Does the test lamp illuminate?
Yes
GO to C5.
No
VERIFY fusible links are OK. If OK, REPAIR circuit SDC02 (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.
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C5 CHECK THE GENERATOR COMMAND LINE FAULT (GENCMD_LF) PID
- NOTE: Many of the PCM PIDs selected will be monitored later in this pinpoint test.
- Select and monitor the following PCM PIDs:
- Generator Monitor (GENMON).
- Generator Command (GENCMD).
- Generator Command Line Fault (GENCMD_LF).
- With the engine still running at idle, monitor the GENCMD_LF PID.
- Is the GENMON_LF PID ON?
Yes
GO to C6.
No
GO to C9.
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C6 CHECK THE GENCOM CIRCUIT FOR A SHORT TO POWER
- Ignition OFF.
- Disconnect: Generator C1104A.
- Ignition ON.
- Measure the voltage between generator C1104A-2, circuit CDC10 (BU/OG), harness side and ground.
- Does voltage read 1 volt or less?
Yes
GO to C7.
No
GO to C11.
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C7 COMPARE THE PCM PIDs GENERATOR MONITOR (GENMON) AND GENERATOR COMMAND (GENCMD)
- Ignition OFF.
- Connect a fused jumper wire between generator C1104A-1, circuit CDC15 (VT), harness side and generator C1104A-2, circuit CDC10 (BU/OG), harness side.
- Key ON Engine OFF (KOEO).
- Monitor the GENMON and GENCMD PIDs while performing a wiggle test on the generator harness.
- Does the GENMON PID read within 5% of the GENCMD PID?
Yes
GO to C8.
No
GO to C12.
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C8 CHECK CIRCUIT CDC10 (BU/OG) FOR DAMAGE OR AN OPEN
- Ignition OFF.
- Disconnect: PCM C175B.
- Inspect the following harness connectors for damaged or pushed-out pins:
- PCM C175B-32, circuit CDC10 (BU/OG).
- Generator C1104A-2, circuit CDC10 (BU/OG).
- Measure the resistance between PCM C175B-32, circuit CDC10 (BU/OG), harness side and generator C1104A-2, circuit CDC10 (BU/OG), 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 CDC10 (BU/OG). CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
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C9 CHECK CIRCUIT CDC10 (BU/OG) FOR SHORT TO GROUND
- Ignition OFF.
- Disconnect: Generator C1104A (if not previously disconnected).
- Measure the resistance between the generator C1104A-2, circuit CDC10 (BU/OG), 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.
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C10 CHECK THE CHARGING SYSTEM CIRCUITS FOR INTERMITTENT FAULTS
- Connect: Generator C1104A.
- Connect: PCM C175B.
- Ignition ON.
- Clear all DTCs.
- Start the engine and let the engine run for 5 minutes.
- Retrieve continuous memory DTCs from all modules.
- Did any charging system DTC get stored into memory?
Yes
INSTALL a new generator. REFER to Generator - 4.0L SOHC Service and Repair or Generator - 4.6L (2V) Service and Repair. 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.
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C11 CHECK FOR SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: PCM C175B.
- Ignition ON.
- Measure the voltage between generator C1104A-2, circuit CDC10 (BU/OG), harness side and ground.
- Does voltage read 0 volt?
Yes
INSTALL a new PCM. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
No
REPAIR circuit CDC10 (BU/OG). CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
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C12 INSPECT GENERATOR CIRCUITS
- Ignition OFF.
- Disconnect: PCM C175B.
- Inspect the following connector pins for damage and/or corrosion, PCM ground C175B-50, circuit GD113 (BK/YE), generator C1104A-1, circuit CDC15 (VT), and generator C1104A-2, circuit CDC10 (BU/OG).
- 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.
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