Toyota 4Runner: Fail-safe Chart

FAIL-SAFE CHART

If a problem occurs in the power steering system, the power steering warning light in the combination meter comes on and the power steering assist is stopped, locked at a particular point or decreased simultaneously to protect the system.

Power Steering System

DTC Code	Detection Condition	Fail-safe Operation
C15F0	Short circuit between power steering solenoid valve terminals SOF+ and ground	Assist force is restricted.
	Short circuit between power steering solenoid valve terminals SOF- and ground	Power assist continues as normal.
	Short circuit between power steering solenoid valve terminals SOF+ and SOF-	Assist force is restricted.
	Power steering solenoid valve open circuit	Assist force is restricted.
C15F1	Steering angle sensor circuit malfunction	The power steering system is limited depending on which ECU has lost communication. For details, refer to Fail-safe Function.
C1544	Engine speed signal malfunction
C1541	Vehicle speed signal malfunction
U0100	Lost Communication with ECM / PCM "A"
U0126	Lost Communication with Steering Angle Sensor Module
U0129	Lost Communication with Brake System Control Module

1. FAIL-SAFE FUNCTION

If the power steering ECU assembly cannot receive the steering angle signal, steering zero point memory, vehicle speed signal or engine speed signal, the power steering warning light in the combination meter illuminates and the vehicle enter a fail-safe mode.

Malfunction Area				Fail-Safe Mode
Steering Angle Signal	Steering Zero Point Memory	Vehicle Speed Signal	Engine Speed Signal	Fail-Safe Mode
X	-	-	-	V-Q control fixed Steering angle compensation disabled Steering wheel return compensation disabled Engine speed compensation normal
-	X	-	-	V-Q control normal Steering angle compensation disabled Steering wheel return compensation disabled Engine speed compensation normal
-	-	X	-	Assume vehicle speed 40 km/h and control each compensation
-	-	-	X	V-Q control normal Steering angle compensation normal Steering wheel return compensation normal Engine speed compensation disabled
X	X	-	-	V-Q control fixed Steering angle compensation disabled Steering wheel return compensation disabled Engine speed compensation normal
X	-	X	-	Constant fluid volume
X	-	-	X	V-Q control characteristics fixed Steering angle compensation disabled Steering wheel return compensation disabled Engine speed compensation disabled
-	X	X	-	V-Q control fixed Steering angle compensation disabled Steering wheel return compensation disabled Engine speed compensation normal
-	X	-	X	V-Q control normal Steering angle compensation disabled Steering wheel return compensation disabled Engine speed compensation disabled
-	-	X	X	Assume vehicle speed 40 km/h and control each compensation Engine speed compensation disabled
-	X	X	X	V-Q control characteristics fixed Steering angle compensation disabled Steering wheel return compensation disabled Engine speed compensation disabled
X	-	X	X	Constant fluid volume
X	X	-	X	V-Q control characteristics fixed Steering angle compensation disabled Steering wheel return compensation disabled Engine speed compensation disabled
X	X	X	-	Constant fluid volume
X	X	X	X	Constant fluid volume

HINT:

X: Malfunction

Fail-safe Chart

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