Electronic Power Steering System

POWER STEERING: ELECTRONIC POWER STEERING SYSTEM: U0073, U0100, U0129, U0293: Control Module Communication Bus OFF

DTC U0073 - Control Module Communication Bus OFF

DTC U0100 - Lost Communication with ECM / PCM "A"

DTC U0129 - Lost Communication with Skid Control ECU

DTC U0293 - Lost Communication with HV ECU

DESCRIPTION

The power steering ECU assembly receives signals from the hybrid vehicle control ECU, skid control ECU and steering control ECU via CAN communication.





HINT:
- When two or more DTCs starting with "U" are output simultaneously, inspect the connectors and wire harness of each ECU.
- If the power steering ECU assembly detects DTC U0129 only, it adjusts the amount of power assistance for driving at a speed of 100 km/h (62 mph) and continues system control.

INSPECTION PROCEDURE

NOTICE:
- Turn the power switch off before measuring the resistances of CAN bus main wires and CAN bus branch wires.
- After the power switch is turned off, check that the key reminder warning system and lighting system are not operating.
- Before measuring the resistance, leave the vehicle as is for at least 1 minute and do not operate the power switch, any other switches, or the doors. If any doors need to be opened in order to check connectors, open the doors and leave them open.

HINT: Operating the power switch, any other switches, or a door triggers related ECU and sensor communication on the CAN. This communication will cause the resistance value to change.

PROCEDURE

1. CHECK FOR OPEN IN CAN BUS WIRE (HV CONTROL ECU MAIN WIRE)





(a) Disconnect HV control ECU connector A61.
(b) Measure the resistance according to the value(s) in the table below.

Standard resistance:





NG -- REPLACE HV CONTROL ECU MAIN WIRE OR CONNECTOR
OK -- Continue to next step.
2. CHECK ECM POWER SOURCE CIRCUIT
(a) Check the ECM power source circuit ECM Power Source Circuit.
NG -- REPAIR OR REPLACE ECM POWER SOURCE CIRCUIT
OK -- REPLACE HV CONTROL ECU