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U1123






U1123-LOSS COMMUNICATION LIN ECU 3





For a complete wiring diagram, refer to the Wiring Information Electrical Diagrams.

- When Monitored:
Continuously while the system is active.

- Set Condition:
The Powertrain Control Module (PCM) is receiving a Local Interface Network (LIN) bus error message.





WARNING: On vehicles equipped with the high voltage system, you must thoroughly read and follow all High Voltage Safety procedures. In addition, before performing any diagnostic or service procedure near a high voltage component, you must perform the High Voltage Power Down. Failure to follow these instructions may result in possible serious or fatal injury

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.

1. DTC IS ACTIVE

NOTE: LIN ECU 2 IS TPIM COOLANT PUMP AND LIN ECU 3 IS THE AUXILIARY ELECTRIC COOLANT PUMP.

1. Turn the ignition on.
2. With the scan tool, View DTCs.
3. Record all DTC information.
4. With the scan tool, clear DTCs.
5. Start the engine and allow it to reach normal operating temperature.
6. Monitor the scan tool for at least two minutes.
7. With the scan tool, View DTCs.

Is the status Active for this DTC?

Yes

- Go To 2

No

- Perform the INTERMITTENT CONDITION diagnostic procedure. Intermittent Condition Test.

2. U1122-LOSS COMMUNICATION LIN ECU 2
1. With the scan tool, View DTCs.

Is the status active for U1122-Loss Communication LIN ECU 2 DTC?

Yes

- Go To 7

No

- Go To 3

3. (F202) FUSED IGNITION SWITCH OUTPUT (OFF-RUN-START) CIRCUIT OPEN OR SHORTED




1. Turn the ignition off
2. Disconnect the HVAC Electric Coolant Pump harness connector.
3. Turn the ignition on.
4. Using a 12-volt test light connected to ground, check the (F202) Fused Ignition Switch Output (OFF-RUN-START) circuit.

Does the test light illuminate brightly?

Yes

- Go To 4

No

- Repair the (F202) Fused Ignition Switch Output (OFF-RUN-START) circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

4. (A501) HVAC ELECTRIC COOLANT PUMP FUSED B(+)




1. Using a 12-volt test light connected to ground, check the (A501) HVAC electric coolant fused B(+) circuit.

Does the test light illuminate brightly?

Yes

- Go To 5

No

- Repair the open or short to ground in the (A501) TPIM Coolant Pump Relay feed circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

5. (Z981) GROUND CIRCUIT OPEN




1. Using a 12-volt test light connected to 12 Volts, check the (Z981) ground circuit.

Does the test light illuminate brightly?

Yes

- Go To 6

No

- Repair the open in the (Z982) ground circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

6. (D500) LIN BUS CIRCUIT OPEN




1. Turn the ignition off.
2. Disconnect the TPIM Coolant Pump harness connector.
3. Disconnect the C4 PCM harness connector.
4. Measure the resistance of the (D500) LIN bus circuit from the C4 PCM harness connector to the TPIM Cooling Pump harness connector.

Is the resistance above 5 Ohms?

Yes

- Repair the open in the (D500) LIN BUS.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Replace the HVAC Electric Coolant Pump.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

7. (D500) LIN BUS CIRCUIT SHORTED TO VOLTAGE




1. Turn the ignition off.
2. Disconnect the HVAC Electric Coolant Pump harness connector.
3. Disconnect the TPIM Cooling Pump harness connector.
4. Disconnect the C4 PCM harness connector.
5. Turn the ignition on.
6. Measure the voltage of the (D500) LIN bus circuit in the TPIM Cooling Pump harness connector.

Is there any voltage present?

Yes

- Repair the short to voltage in the (D500) LIN BUS.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Go To 8

8. (D500) LIN BUS CIRCUIT SHORTED TO GROUND




1. Turn the ignition off.
2. Measure the resistance between ground and the (D500) LIN bus circuit in the HVAC Electric Coolant Pump harness connector.

Is the resistance above 10k Ohms?

Yes

- Go To 9

No

- Repair the short to ground in the (D500) LIN BUS.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

9. (D500) LIN BUS CIRCUITS OPEN





CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals, resulting in poor terminal to pin connection. Install PCM Pinout Box 8815 to perform diagnosis.

1. Measure the resistance of the (D500) LIN bus circuit from the appropriate terminal of the PCM Pinout Box 8815 and TPIM Cooling Pump harness connector.
2. Measure the resistance of the (D500) LIN bus circuit from the appropriate terminal of the PCM Pinout Box 8815 and HVAC Electric Coolant Pump harness connector.

Is the resistance below 5 Ohms?

Yes

- Go To 10

No

- Repair the open in the (D500) LIN BUS.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

10. TPIM COOLANT PUMP
1. Reconnect the C4 PCM and TPIM Coolant Pump harness connectors.
2. Turn the ignition on.
3. With the scan tool, View DTCs.

Is the status active for DTC U1122 and U1123?

Yes

- Replace TPIM Coolant Pump.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Go To 11

11. ELECTRIC COOLANT PUMP HVAC
1. Turn the ignition off.
2. Reconnect HVAC Electric Pump harness connector.
3. Disconnect TIPM Coolant Pump harness connector.
4. Turn the ignition on.
5. With the scan tool, View DTCs.

Is the status active for DTC U1122 and U1123?

Yes

- Replace HVAC electric coolant pump.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Go To 12

12. POWERTRAIN CONTROL MODULE (PCM)
1. Using the wiring diagram/schematic as a guide, inspect the wiring and electrical connectors between the TPIM Cooling Pump (HEV) and the PCM.
2. Look for any chafed, pierced, pinched, or partially broken wires.
3. Look for broken, bent, pushed out or corroded terminals.
4. Monitor the scan tool data relative to this circuit and wiggle test the wiring and connectors.
5. Look for the data to change or for the DTC to reset during the wiggle test.
6. Perform any Technical Service Bulletins that may apply.

Were any problems found?

Yes

- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Replace the Powertrain Control Module (PCM).
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

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