U0121

POWER STEERING: ELECTRONIC POWER STEERING SYSTEM:

DTC U0121 - Lost Communication with Anti-lock Brake System (ABS) Control Module

DESCRIPTION

The power steering ECU assembly receives signals from the ECM, 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 U0121 only, it adjusts the amount of power assistance for a speed of 100 km/h (62 mph) and continues system control.

INSPECTION PROCEDURE

PROCEDURE

1. CONFIRM MODEL
Result:

B -- CHECK OPEN IN CAN BUS WIRE (SKID CONTROL ECU BRANCH LINE)
A -- Continue to next step.
2. CHECK OPEN IN CAN BUS WIRE (SKID CONTROL ECU BRANCH LINE)
(a) Turn the engine switch off.
(b) Disconnect the skid control ECU connector (J77).

NG -- REPAIR OR REPLACE SKID CONTROL ECU BRANCH WIRE OR CONNECTOR (CAN-H, CAN-L)
OK -- Continue to next step.
3. CHECK WIRE HARNESS (IG1, GND1)
(a) Disconnect the skid control ECU connectors (J78) and (A35).

(b) Measure the resistance according to the value(s) in the table below.
Standard resistance:

NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- REPLACE SKID CONTROL ECU
4. CHECK OPEN IN CAN BUS WIRE (SKID CONTROL ECU BRANCH LINE)
(a) Turn the engine switch off.
(b) Disconnect the skid control ECU connector (A14).

NG -- REPAIR OR REPLACE SKID CONTROL ECU BRANCH WIRE OR CONNECTOR (CAN-H, CAN-L)
OK -- Continue to next step.
5. CHECK WIRE HARNESS (IG1, GND1)

(a) Measure the resistance according to the value(s) in the table below.
Standard resistance:

(b) Measure the voltage according to the value(s) in the table below.
Standard voltage:

NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- REPLACE SKID CONTROL ECU (BRAKE ACTUATOR)