Pinpoint Test C: DTC U0120:13

Pinpoint Test





Pinpoint Test C: DTC U0120:13

Refer to Wiring Diagram Set 12, Charging System for schematic and connector information Electrical Diagrams.

Normal Operation

The charging system supplies voltage to the battery and the vehicle electrical system through the battery B+ cable. The PCM monitors the generator output through a dedicated Local Interconnect Network (LIN) communication circuit. The generator uses this LIN (Local Interconnect Network) circuit to communicate the desired voltage setpoint from the PCM to the voltage regulator. The generator also uses this LIN (Local Interconnect Network) circuit to communicate the generator load and error conditions to the PCM.

- DTC U0120:13 (Lost Communication with Starter/Generator Control Module: Circuit Open)- Sets when the PCM does not detect communication through the LIN (Local Interconnect Network) circuit. This can be a result of an open or short in the LIN (Local Interconnect Network) circuit. This DTC also sets if the B+ circuit is open.

This pinpoint test is intended to diagnose the following:

- Wiring, terminals or connectors

- Generator

- PCM

PINPOINT TEST C : DTC U0120:13

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 GENERATOR CONNECTIONS

- Ignition OFF.

- Inspect generator C102A connection. Connector should be installed correctly and tight.

- Inspect generator C102A for bent and/or pushed-out pins.

- Inspect generator C102B, B+ circuit SBF01 (RD) connection. The connection should be tight.

- Measure the battery voltage.





- Measure the voltage between generator C102B, B+ circuit SBF01 (RD) and ground.





Is the generator C102B connection tight and does the generator B+ measure battery voltage within ±0.5 volt?

Yes
GO to C2.

No
TIGHTEN or INSTALL a new C102B (B+ nut) or REPAIR connection as needed. REFER to Specifications. VERIFY the high current fuse assembly is OK. If the fuse assembly is OK, REPAIR circuit SBF01 (RD). If the fuse assembly is not OK, REFER to the Wiring Diagrams to identify the possible causes of the circuit short Electrical Diagrams. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.

C2 CHECK THE GENERATOR LIN (Local Interconnect Network) CIRCUIT FOR A SHORT TO VOLTAGE

- Ignition OFF.

- Disconnect: Generator C102A.

- Disconnect: PCM C175E.

- Ignition ON.

- Measure the voltage between generator C102A-1, circuit CDC15 (VT), harness side and ground.





Is any voltage present?

Yes
REPAIR circuit CDC15 (VT) for a short to voltage. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.

No
GO to C3.

C3 CHECK THE GENERATOR LIN (Local Interconnect Network) CIRCUIT FOR A SHORT TO GROUND

- Ignition OFF.

- Measure the resistance between the generator C102A-1, circuit CDC15 (VT), harness side and ground.





Is the resistance greater than 10,000 ohms?

Yes
GO to C4.

No
REPAIR circuit CDC15 (VT) for a short to ground. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.

C4 CHECK THE GENERATOR LIN (Local Interconnect Network) CIRCUIT FOR AN OPEN

- Inspect the following harness connectors for damaged or pushed-out pins:
- PCM C175E-39, circuit CDC15 (VT)

- Generator C102A-1, circuit CDC15 (VT)


- Measure the resistance between PCM C175E-39, circuit CDC15 (VT), harness side and generator C102A-1, circuit CDC15 (VT), harness side.





Are the connectors and pins free of damage and is the resistance less than 5 ohms?

Yes
INSTALL a new generator. Refer to Generator Service and Repair. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.

If DTC U0120:13 returns, INSTALL a new PCM. TEST the system for normal operation.

No
REPAIR circuit CDC15 (VT) for an open. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.