Electronic Power Steering System - Diagnosis System

Lexus IS250 IS220d GSE20 ALE20 - POWER STEERING


ELECTRONIC POWER STEERING SYSTEM - DIAGNOSIS SYSTEM

DESCRIPTION

Connecting the intelligent tester to the vehicle and reading various data output from the power steering ECU assembly is the only difference between usual troubleshooting procedures and those for a vehicle with a diagnostic system.


The power steering ECU assembly records DTCs when the ECU detects a malfunction in the computer itself or in its circuits.


To check the DTCs, connect the intelligent tester to the DLC3. The intelligent tester enables you to erase the DTCs and check the freeze frame data and various forms of steering data.

CHECK DLC3
Electronic Power Steering System - Diagnosis System. POWER STEERING. Lexus IS250 IS220d GSE20 ALE20

Check the DLC3.


The power steering ECU assembly uses CAN and ISO 15765-4 communication protocol. The terminal arrangement of the DLC3 complies with SAE J1962 and matches the ISO 15765-4 format.

Symbols (Terminal No.)Terminal DescriptionConditionSpecified Condition
SIL (7) - SG (5)Bus "+" lineDuring communicationPulse generation
CG (4) - Body groundChassis groundAlwaysBelow 1 Ω
SG (5) - Body groundSignal groundAlwaysBelow 1 Ω
BAT (16) - Body groundBattery positiveAlways11 to 14 V
CANH (6) - CANL (14)HIGH-level CAN bus lineEngine switch off54 to 67 Ω
CANH (6) - Battery positiveHIGH-level CAN bus lineEngine switch off1 MΩ or higher
CANH (6) - CG (4)HIGH-level CAN bus lineEngine switch off3 kΩ or higher
CANL (14) - Battery positiveLOW-level CAN bus lineEngine switch off1 MΩ or higher
CANL (14) - CG (4)LOW-level CAN bus lineEngine switch off3 kΩ or higher
  • HINT:
  • Connect the intelligent tester cable to the DLC3, turn the engine switch on (IG), and attempt to use the tester. If the screen displays a communication error message, a problem exists on the vehicle side or the tester side.
If communication is normal when connecting the tester to another vehicle, inspect the DLC3 on the original vehicle.
If communication is still not possible when connecting the tester to another vehicle, the problem is probably in the tester itself. Consult the Service Department listed in the tester's operator's manual.
P/S WARNING LIGHT
Electronic Power Steering System - Diagnosis System. POWER STEERING. Lexus IS250 IS220d GSE20 ALE20

Check that the PS warning light comes on when the engine switch is turned on (IG) and goes off in approximately 3 seconds.

If the warning light does not come on or remains on, inspect the PS warning light circuit.

Trouble AreaSee Procedure
PS warning light circuit (Remains on)
PS warning light circuit (Does not come on)