Pinpoint Test U: Dual Generator Upper Fault Detected (P0620)
Pinpoint Test
Pinpoint Test U: Dual Generator Upper Fault Detected (P0620)
Refer to Wiring Diagram Set 12, Charging System for schematic and connector information. Diagrams By Number
Normal Operation
The generator output is determined by the voltage of the A circuit 35 (OG/LB). The A circuit voltage is compared to a set voltage internal to the voltage regulator and the voltage regulator controls the generator field current to maintain the correct generator output. The set voltage varies with temperature and is typically higher in cold temperatures and lower in warm temperatures.
This pinpoint test is intended to diagnose the following:
- Upper generator disconnected
- B+ circuit fusible links
- B+ circuit open (upper)
- A circuit open
- I circuit open or short to ground
- Upper generator
PINPOINT TEST U: DUAL GENERATOR UPPER FAULT DETECTED (P0620)
-------------------------------------------------
U1 CHECK THE UPPER GENERATOR CONNECTIONS
- Ignition OFF.
- Disconnect: Upper Generator C1104c and C1104a.
- Check the upper generator connectors for damage and correct connection.
- Connect: Upper Generator C1104c and C1104a.
- Are the upper generator connectors OK and correctly connected?
Yes
GO to U2.
No
REPAIR the connections as necessary. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
-------------------------------------------------
U2 CHECK THE UPPER GENERATOR B+ VOLTAGE
- Measure the voltage between the B+ terminal of the upper generator C1104c, circuit 1119 (RD), harness side and ground.
- Is the voltage equal to battery voltage?
Yes
GO to U3.
No
CHECK the B+ circuit 1119 (RD) including the fusible links. REPAIR as necessary. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
-------------------------------------------------
U3 CHECK THE UPPER GENERATOR A CIRCUIT FOR VOLTAGE
- Disconnect: Upper Generator C1104a.
- Measure the voltage between the upper generator C1104a-3, A circuit 35 (OG/LB), harness side and ground.
- Is the voltage equal to battery voltage?
Yes
GO to U4.
No
CHECK the upper generator A circuit 35 (OG/LB) including the fusible links. REPAIR as necessary. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
-------------------------------------------------
U4 CHECK THE UPPER GENERATOR I CIRCUIT FOR VOLTAGE
- Ignition ON.
- With the Key ON Engine OFF (KOEO), measure the voltage between the upper generator C1104a-1, I circuit 904 (LG/RD), harness side and ground.
- Is the voltage greater than 10 volts?
Yes
GO to U6.
No
GO to U5.
-------------------------------------------------
U5 CHECK THE UPPER GENERATOR I CIRCUIT FOR AN OPEN OR SHORT TO GROUND
- Ignition OFF.
- Disconnect: PCM C1381e.
- Measure the resistance between the generator C1104a-1, I circuit 904 (LG/RD), harness side and the PCM C1381e-1, circuit 1183 (WH/YE), harness side; and between the generator C1104a-1, I circuit 904 (LG/RD), harness side and ground.
- Is the resistance less than 5 ohms between the generator and the PCM, and greater than 10,000 ohms between the generator and ground?
Yes
GO to U7.
No
REPAIR the I circuit 1183 (WH/YE) or 904 (LG/RD). CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
-------------------------------------------------
U6 CHECK THE UPPER GENERATOR VOLTAGE
- Connect: Upper Generator C1104a.
- Disconnect: Lower Generator C1251a.
- Start the engine.
- NOTE: After starting the engine, wait at least 2 minutes for the glow plugs to stop cycling. If the glow plug system is cycling, the PCM will not provide voltage on the lower generator I circuit.
- With the engine running, measure the voltage at the battery(s).
- Is the voltage greater than 13 volts?
Yes
The system is operating normally. CONNECT all of the connectors. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
No
INSTALL a new upper generator. REFER to Generator - Diesel Engines, Dual Generators . CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
-------------------------------------------------
U7 CHECK FOR CORRECT PCM OPERATION
- Disconnect all of the PCM connectors.
- Check for:
- corrosion.
- pushed-out pins.
- Connect all of the PCM connectors and make sure they seat correctly.
- Operate the system and verify the concern is still present.
- Is the concern still present?
Yes
INSTALL a new PCM. REPEAT the self-test. TEST the system for normal operation.
No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
-------------------------------------------------