IN–38INTRODUCTION – HOW TO TROUBLESHOOT ECU CONTROLLED SYSTEMS
IN
ELECTRONIC CIRCUIT INSPECTION
PROCEDURE
1. BASIC INSPECTION
(a) WHEN MEASURING RESISTANCE OF
ELECTRONIC PARTS
(1) Unless otherwise stated, all resistance
measurements should be made at an ambient
temperature of 20
C (68F). Resistance
measurements may be inaccurate if measured
at high temperatures, i.e. immediately after the
vehicle has been running. Measurements should
be made after the engine has cooled down.
(b) HANDLING CONNECTORS
(1) When disconnecting a connector, first squeeze
the mating halves tightly together to release the
lock, and then press the lock claw and separate
the connector.
(2) When disconnecting a connector, do not pull on
the harnesses. Grasp the connector directly and
separate it.
(3) Before connecting a connector, check that there
are no deformed, damaged, loose or missing
terminals.
(4) When connecting a connector, press firmly until
it locks with a "click" sound.
(5) If checking a connector with a TOYOTA
electrical tester, check the connector from the
backside (harness side) using a mini test lead.
NOTICE:
• As a waterproof connector cannot be
checked from the backside, check it by
connecting a sub-harness.
• Do not damage the terminals by moving
the inserted tester needle.
(c) CHECKING CONNECTORS
(1) Checking when a connector is connected:
Squeeze the connector together to confirm that
they are fully connected and locked.
(2) Checking when a connector is disconnected:
Pull the wire harness lightly from the backside of
the connector. Visually check for the following: 1)
unlatched terminals, missing terminals, loose
crimps and broken conductor wires; 2)
corrosion, metallic matter, foreign matter and
water; and 3) bent, rusted, overheated,
contaminated and deformed terminals.
D100803E01
D100734E01
PS–16POWER STEERING – ELECTRONIC POWER STEERING SYSTEM
PS
FAIL-SAFE CHART
If a problem occurs in the electric power steering system, the
P/S warning light will come on in the combination meter and
steering power assist will be stopped, fixed at a particular
point, or decreased simultaneously to protect the system.
Electronic power steering system
HINT:
The amount of power assist may be decreased to prevent the
motor and ECUs from overheating if the steering wheel is
continuously turned when the vehicle is either stopped or
driven at a low speed, or if the steering wheel is kept at either
full lock position for a long time. In such cases, the amount of
power assist returns to normal if the steering wheel is not
turned for approximately 10 minutes with the engine idling.
DTC No. Detection Condition Fail-safe
C1511/11 Torque sensor malfunction Power assist stops
C1512/11
C1513/11
C1514/11
C1521/25 Motor malfunction
C1524/24
C1528/12 Motor rotation angle sensor malfunction
C1531/25 ECU malfunction
C1532/25
C1534/25
C1551/25 IG power source voltage error
C1552/22 PIG power source voltage error
C1554/23 Power source relay malfunction
C1555/25 Motor relay malfunction
C1533/25 ECU malfunction Assist force restricted
U0073/49 CAN bus malfunction Amount of power assist is locked at 140 km/h
(87.5 mph) level of power assist
U0121/42 Skid control ECU communication error
U0105/41 ECM communication error Power assist stops
POWER STEERING – ELECTRONIC POWER STEERING SYSTEMPS–17
PS
DATA LIST / ACTIVE TEST
1. READ DATA LIST
HINT:
Using the intelligent tester's DATA LIST allows switch,
sensor, actuator and other item values to be read without
removing any parts. Reading the DATA LIST early in
troubleshooting is one way to save time.
(a) Connect the intelligent tester (with CAN VIM) to the
DLC3.
(b) Turn the ignition switch ON and press the intelligent
tester main switch ON.
(c) Read the DATA LIST by following the directions on
the tester screen.
Tester Display Measurement Item/Range Normal Condition Reference Value
BATTERY VOLTAGE Battery voltage:
Min.: 0 V
Max.: 25.5 V- 10 to 14 V
SPD Vehicle speed from meter:
Min.: 0 km/h (0 mph)
Max.: 300 km/h (187.5 mph)Vehicle stopped 0 km/h (0 mph)
Vehicle driven at constant speed No significant fluctuation
SPD SIG INVALID Record of vehicle speed signal
invalid:
REC or UNREC- UNREC
ENGINE REV Show the engine revolution:
Min.: 0 rpm
Max.: 12800 rpmEngine is running at a constant
speedNo significant fluctuation
ENG REV INTER Record of engine revolution
signal interruption
REC or UNREC- UNREC
MOTOR ACTUAL Amount of current to motor:
Min.: -327.68 A
Max.: 327.67 APower steering is in operation Value changes in proportion to
steering effort
COMMAND VALUE Demanded amount of current to
motor:
Min.: -327.68 A
Max.: 327.68 APower steering is in operation Value changes in proportion to
steering effort
STR ANGL VEL Steering angle speed:
Min.: -32768
/sec.
Max.: 32767
/sec.Steering wheel is turned Value changes in proportion to
steering effort
STEERING TORQUE Steering wheel torque:
Min.: -7 Nm
Max.: 7 Nm--
THERMISTOR TEMP ECU substrate temperature:
Min.: -40
C
Max.: 150
CIgnition switch ON -
PIG SUPPLY Power source voltage to activate
motor:
Min.: 0 V
Max.: 20.1531 VPower steering in operation 10 to 14 V
IG SUPPLY ECU power source voltage:
Min.: 0 V
Max.: 20.1531 VIgnition switch ON 10 to 14 V
MTR OVERHEAT Continuous overheat prevention
control record:
REC or UNREC- UNREC
MTR LOW POWER PIG power source voltage drop
record:
REC or UNREC- UNREC
