Lexus RX (RX 350L, RX450h) 2016-2024 Repair Manual: Diameter of the Tire is not Uniform (C1337)

DESCRIPTION

The 4WD ECU assembly stores this DTC if a difference in tire size is detected.

DTC No.	Detection Item	DTC Detection Condition	Trouble Area
C1337	Diameter of the Tire is not Uniform	When the following continues for 36 seconds or more: At a vehicle speed of 30 km/h (18.6 mph) or more, the average speed difference between the front wheel and rear wheel is 4% or more.	Tire size or pressure (front and rear tires) Speed sensor circuit Front speed sensor Rear speed sensor Front skid control sensor wire (w/ AVS) Rear No. 1 skid control sensor wire (w/ AVS) Front speed sensor rotor (Front axle hub sub-assembly) Rear speed sensor rotor (Rear axle hub and bearing assembly) Wire harness and connector Skid control ECU (Brake actuator assembly) 4WD ECU assembly

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

When the 4WD ECU assembly is replaced with a known good one from another vehicle, it is necessary to perform calibration.

Click here

HINT:

Check the condition of each related circuit connector before troubleshooting.

Click here

PROCEDURE

1.	CHECK TIRE CONDITION

(a) Check the size and condition of all 4 tires.

HINT:

This DTC is output when tire deformation or a difference in tire size is detected.

OK:

The diameter and air pressure of all 4 tires are the same.

NG

PERFORM AIR PRESSURE ADJUSTMENT OR REPLACE TIRES SO THAT ALL 4 TIRES ARE SAME IN SIZE

OK

2.	CHECK FOR DTC

(a) Clear the DTCs.

Chassis > Four Wheel Drive > Clear DTCs

(b) Start the engine.

(c) Drive the vehicle at a speed of 30 km/h (19 mph) or more so that the same DTC is output.

Chassis > Four Wheel Drive > Trouble Codes

(d) Check if the speed sensor DTC (vehicle stability control system DTC) is output.

Chassis > Brake/EPB > Trouble Codes

(e) Read the DTCs using the Techstream.

Result	Proceed to
Only DTC C1377 is output (w/o AVS)	A
Only DTC C1377 is output (w/ AVS)	B
DTCs are not output	C
Speed sensor DTCs (vehicle stability control system DTC) are output	D

B

GO TO STEP 4

C

CHECK FOR INTERMITTENT PROBLEMS

D

REPAIR CIRCUIT INDICATED BY OUTPUT CODE (VEHICLE STABILITY CONTROL SYSTEM)

A

3.	CHECK HARNESS AND CONNECTOR (SPEED SENSOR - BRAKE ACTUATOR ASSEMBLY)

(a) Make sure that there is no looseness at the locking part and the connecting part of the connectors.

(b) Turn the engine switch off.

(c) Disconnect the A41 skid control ECU (brake actuator assembly) connector.

(d) Disconnect the A92, A93, T1 and/or T2 speed sensor connector(s).

(e) Measure the resistance according to the value(s) in the table below.

Standard Resistance:

for Front RH:

Tester Connection	Condition	Specified Condition
A41-7 (FR+) - A93-3 (FR+)	Always	Below 1 Ω
A41-6 (FR-) - A93-4 (FR-)	Always
A41-7 (FR+) or A93-3 (FR+) - Body ground and other terminals	Always	10 kΩ or higher
A41-6 (FR-) or A93-4 (FR-) - Body ground and other terminals	Always

for Front LH:

Tester Connection	Condition	Specified Condition
A41-22 (FL+) - A92-3 (FL+)	Always	Below 1 Ω
A41-21 (FL-) - A92-4 (FL-)	Always
A41-22 (FL+) or A92-3 (FL+) - Body ground and other terminals	Always	10 kΩ or higher
A41-21 (FL-) or A92-4 (FL-) - Body ground and other terminals	Always

for Rear RH:

Tester Connection	Condition	Specified Condition
A41-20 (RR+) - T2-2 (RR+)	Always	Below 1 Ω
A41-19 (RR-) - T2-1 (RR-)	Always
A41-20 (RR+) or T2-2 (RR+) - Body ground and other terminals	Always	10 kΩ or higher
A41-19 (RR-) or T2-1 (RR-) - Body ground and other terminals	Always

for Rear LH:

Tester Connection	Condition	Specified Condition
A41-5 (RL+) - T1-3 (RL+)	Always	Below 1 Ω
A41-4 (RL-) - T1-1 (RL-)	Always
A41-5 (RL+) or T1-3 (RL+) - Body ground and other terminals	Always	10 kΩ or higher
A41-4 (RL-) or T1-1 (RL-) - Body ground and other terminals	Always

(f) Connect the A92, A93, T1 and/or T2 speed sensor connector(s).

(g) Connect the A41 skid control ECU (brake actuator assembly) connector.

OK

GO TO STEP 6

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

4.	CHECK HARNESS AND CONNECTOR (SKID CONTROL SENSOR WIRE - BRAKE ACTUATOR ASSEMBLY)

(a) Make sure that there is no looseness at the locking part and the connecting part of the connectors.

(b) Disconnect the A41 skid control ECU (brake actuator assembly) connector.

(c) Disconnect the A90, A91, T7 and/or T8 skid control sensor wire connector(s).

(d) Measure the resistance according to the value(s) in the table below.

Standard Resistance:

for Front RH:

Tester Connection	Condition	Specified Condition
A41-7 (FR+) - A91-3 (FR+)	Always	Below 1 Ω
A41-6 (FR-) - A91-4 (FR-)	Always
A41-7 (FR+) or A91-3 (FR+) - Body ground and other terminals	Always	10 kΩ or higher
A41-6 (FR-) or A91-4 (FR-) - Body ground and other terminals	Always

for Front LH:

Tester Connection	Condition	Specified Condition
A41-22 (FL+) - A90-3 (FL+)	Always	Below 1 Ω
A41-21 (FL-) - A90-4 (FL-)	Always
A41-22 (FL+) or A90-3 (FL+) - Body ground and other terminals	Always	10 kΩ or higher
A41-21 (FL-) or A90-4 (FL-) - Body ground and other terminals	Always

for Rear RH:

Tester Connection	Condition	Specified Condition
A41-20(RR+) - T7-2 (RR+)	Always	Below 1 Ω
A41-19 (RR-) - T7-1 (RR-)	Always
A41-20 (RR+) or T7-2 (RR+) - Body ground and other terminals	Always	10 kΩ or higher
A41-19 (RR-) or T7-1 (RR-) - Body ground and other terminals	Always

for Rear LH:

Tester Connection	Condition	Specified Condition
A41-5 (RL+) - T8-3 (RL+)	Always	Below 1 Ω
A41-4 (RL-) - T8-1 (RL-)	Always
A41-5 (RL+) or T8-3 (RL+) - Body ground and other terminals	Always	10 kΩ or higher
A41-4 (RL-) or T8-1 (RL-) - Body ground and other terminals	Always

(e) Connect the A90, A91, T7 and/or T8 skid control sensor wire connector(s).

(f) Connect the A41 skid control ECU (brake actuator assembly) connector.

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

5.	INSPECT SKID CONTROL SENSOR WIRE

(a) Make sure that there is no looseness at the locking part and the connecting part of the connectors.

(b) Turn the engine switch off.

(c) Disconnect the A90, A91, z14 and/or z15 front skid control sensor wire connector(s).

(d) Measure the resistance according to the value(s) in the table below.

*A	for RH	*B	for LH
*1	Front Skid Control Sensor Wire	-	-
*a	Front view of wire harness connector (to Vehicle Side Connector)	*b	Front view of wire harness connector (to Front Speed Sensor Side Connector)

Standard Resistance:

for Front Skid Control Sensor Wire RH:

Tester Connection	Condition	Specified Condition
z15-1 (FR+) - A91-3 (FR+)	Always	Below 1 Ω
z15-2 (FR-) - A91-4 (FR-)	Always
z15-1 (FR+) or A91-3 (FR+) - Body ground and other terminals	Always	10 kΩ or higher
z15-2 (FR-) or A91-4 (FR-) - Body ground and other terminals	Always

for Front Skid Control Sensor Wire LH:

Tester Connection	Condition	Specified Condition
z14-1 (FL+) - A90-3 (FL+)	Always	Below 1 Ω
z14-2 (FL-) - A90-4 (FL-)	Always
z14-1 (FL+) or A90-3 (FL+) - Body ground and other terminals	Always	10 kΩ or higher
z14-2 (FL-) or A90-4 (FL-) - Body ground and other terminals	Always

(e) Connect the A90, A91, z14 and/or z15 front skid control sensor wire connector(s).

(f) Disconnect the T7, T8, z22 and/or z23 rear No. 1 skid control sensor wire connector(s).

(g) Measure the resistance according to the value(s) in the table below. Standard Resistance: for Rear No. 1 Skid Control Sensor Wire RH: Tester Connection Condition Specified Condition z22-1 (RR+) - T7-2 (RR+) Always Below 1 Ω z22-3 (RR-) - T7-1 (RR-) Always z22-1 (RR+) or T7-2 (RR+) - Body ground and other terminals Always 10 kΩ or higher z22-3 (RR-) or T7-1 (RR-) - Body ground and other terminals Always for Rear No. 1 Skid Control Sensor Wire LH: Tester Connection Condition Specified Condition z23-1 (RL+) - T8-3 (RL+) Always Below 1 Ω z23-3 (RL-) - T8-1 (RL-) Always z23-1 (RL+) or T8-3 (RL+) - Body ground and other terminals Always 10 kΩ or higher z23-3 (RL-) or T8-1 (RL-) - Body ground and other terminals Always

*1 Rear No. 1 Skid Control Sensor Wire RH *2 Rear No. 1 Skid Control Sensor Wire LH *a Front view of wire harness connector (to Vehicle Side Connector) *b Front view of wire harness connector (to Rear Speed Sensor Side Connector)

(h) Connect the T7, T8, z22 and/or z23 rear No. 1 skid control sensor wire connector(s).

NG

REPAIR OR REPLACE SKID CONTROL SENSOR WIRE

OK

6.	PERFORM TEST MODE (SIGNAL CHECK)

(a) Turn the engine switch off.

(b) Perform the sensor check in the Test Mode procedure.

Click here

Chassis > Brake/EPB > Utility

Tester Display
Signal Check

OK:

All Test Mode (signal check) inspection items are normal.

NG

GO TO STEP 8

OK

7.	RECONFIRM DTC

(a) Clear the DTCs.

Click here

Chassis > Four Wheel Drive > Clear DTCs

(b) Start the engine.

(c) Drive the vehicle at a speed of 30 km/h (19 mph) or more and check that the same DTC is output.

Click here

Chassis > Four Wheel Drive > Trouble Codes

Result	Proceed to
DTC is not output	A
DTC is output	B

A

CHECK FOR INTERMITTENT PROBLEMS

B

REPLACE BRAKE ACTUATOR ASSEMBLY

8.	CHECK SPEED SENSOR ROTOR

(a) Turn the engine switch off.

(b) Remove the front speed sensor rotor (front axle hub sub-assembly) or rear speed sensor rotor (rear axle hub and bearing assembly).

for Front: Click here

for Rear: Click here

(c) Check the speed sensor rotor.

OK:

There is no foreign matter, scratches or oil on the rotors.

NOTICE:

Check the speed sensor signal after cleaning or replacement.

Click here

NG

CLEAN OR REPLACE SPEED SENSOR ROTOR

OK

9.	REPLACE SPEED SENSOR

(a) Turn the engine switch off.

(b) Replace the front speed sensor or the rear speed sensor.

for Front: Click here

for Rear: Click here

NOTICE:

Check the speed sensor signal after replacement.

Click here

NEXT

10.	RECONFIRM DTC

(a) Clear the DTCs.

Click here

Chassis > Four Wheel Drive > Clear DTCs

(b) Start the engine.

(c) Drive the vehicle at a speed of 30 km/h (19 mph) or more and check that the same DTC is output.

Click here

Chassis > Four Wheel Drive > Trouble Codes

Result	Proceed to
DTC is output	A
DTC is not output	B

HINT:

Reinstall the sensor, connectors, etc. and restore the vehicle to its prior condition before rechecking DTCs.

B

END

A

11.	REPLACE BRAKE ACTUATOR ASSEMBLY

(a) Replace the skid control ECU (brake actuator assembly).

Click here

NEXT

12.	RECONFIRM DTC

(a) Clear the DTCs.

Click here

Chassis > Four Wheel Drive > Clear DTCs

(b) Start the engine.

(c) Drive the vehicle at a speed of 30 km/h (19 mph) or more and check that the same DTC is output.

Click here

Chassis > Four Wheel Drive > Trouble Codes

Result	Proceed to
DTC is not output	A
DTC is output	B

A

END

B

REPLACE 4WD ECU ASSEMBLY