Vehicle Speed Signal Circuit between Navigation ECU and Combination Meter [06/2018 - 09/2022]: Procedure

WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2022 Lexus ES 350, 2022 Lexus ES 250, 2021 Lexus ES 350, 2021 Lexus ES 250, and 2020 Lexus ES 350. However, it is still accessible from the selected car via links, so may be relevant.

CHECK COMBINATION METER ASSEMBLY (OUTPUT WAVEFORM)

Check the output waveform.

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

*a	Component with harness connected (Combination Meter Assembly)

Remove the combination meter assembly with the connector still connected.
Connect an oscilloscope to terminal G17-19 (+S) and body ground.
Turn the engine switch on (IG).
Turn a wheel slowly.

Check the signal waveform according to the condition(s) in the table below.

Item	Condition
Measurement terminal	G17-19 (+S) - Body ground
Tool setting	5 V/DIV., 20 ms./DIV.
Vehicle condition	Wheel being rotated

The waveform is similar to that shown in the illustration.

HINT:

When the system is functioning normally, one wheel revolution generates 4 pulses. As the vehicle speed increases, the width indicated by (A) in the illustration narrows.

Result

Proceed to
OK
NG

Result:

GO TO METER / GAUGE SYSTEM. Refer to Speed Signal Circuit [06/2018 - 08/2020] , or refer to Speed Signal Circuit [08/2020 - 09/2022]

Result:

See step 2

INSPECT NAVIGATION ECU (INPUT WAVEFORM)

Check the input waveform.

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

*a	Component with harness connected (Navigation ECU)

Remove the navigation ECU with the connector(s) still connected.
Connect an oscilloscope to terminal G14-9 (SPD) and body ground.
Turn the engine switch on (IG).
Turn a wheel slowly.

Check the signal waveform according to the condition(s) in the table below.

Item	Condition
Measurement terminal	G14-9 (SPD) - Body ground
Tool setting	5 V/DIV., 20 ms./DIV.
Vehicle condition	Wheel being rotated

The waveform is similar to that shown in the illustration.

HINT:

When the system is functioning normally, one wheel revolution generates 4 pulses. As the vehicle speed increases, the width indicated by (A) in the illustration narrows.

Result

Proceed to
OK
NG

Result:

PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE. Refer to PROBLEM SYMPTOMS TABLE [06/2018 - 10/2019] , or refer to PROBLEM SYMPTOMS TABLE [10/2019 - 08/2020] , or refer to PROBLEM SYMPTOMS TABLE [08/2020 - 08/2021] , or refer to PROBLEM SYMPTOMS TABLE [08/2021 - 09/2022]

Result:

REPAIR OR REPLACE HARNESS OR CONNECTOR