Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual: Tachometer Malfunction

DESCRIPTION

In this circuit, the combination meter assembly receives engine speed signals from the ECM via CAN communication. The combination meter assembly displays the engine speed calculated based on the data received from the ECM.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

HINT:

Active Test cannot be performed on the tachometer for TFT meter type.

PROCEDURE

1.	CHECK CAN COMMUNICATION SYSTEM

(a) Check if CAN communication DTCs are output.

Click here

Result	Proceed to
CAN communication DTCs are not output.	A
CAN communication DTCs are output.	B

B

GO TO CAN COMMUNICATION SYSTEM

A

2.	CONFIRM MODEL

(a) Choose the model to be inspected.

Result	Proceed to
for Optitron Meter Type	A
for TFT Meter Type	B

B

GO TO STEP 4

A

3.	PERFORM ACTIVE TEST USING TECHSTREAM (TACHOMETER OPERATION)

(a) Connect the Techstream to the DLC3.

(b) Turn the engine switch on (IG).

(c) Turn the Techstream on.

(d) Enter the following menus: Body Electrical / Combination Meter / Active Test.

(e) Perform the Active Test according to the display on the Techstream.

Body Electrical > Combination Meter > Active Test

Tester Display	Measurement Item	Control Range	Diagnostic Note
TachoMeter Operation	Tachometer	OFF, 0, 1000, 2000, 3000, 4000, 5000, 6000, 7000	-

Body Electrical > Combination Meter > Active Test

Tester Display
TachoMeter Operation

OK:

Tachometer indication is normal.

NG

REPLACE COMBINATION METER ASSEMBLY

OK

4.	READ VALUE USING TECHSTREAM (ENGINE RPM)

(a) Connect the Techstream to the DLC3.

(b) Turn the engine switch on (IG).

(c) Turn the Techstream on.

(d) Enter the following menus: Body Electrical / Combination Meter / Data List.

(e) Read the Data List according to the display on the Techstream.

Body Electrical > Combination Meter > Data List

Tester Display	Measurement Item	Range	Normal Condition	Diagnostic Note
Engine Rpm	Engine speed	Min.: 0 rpm, Max.: 12750 rpm	Almost the same as actual tachometer	-

Body Electrical > Combination Meter > Data List

Tester Display
Engine Rpm

OK:

Engine speed displayed on the Techstream is almost the same as the tachometer indication.

NG

REPLACE COMBINATION METER ASSEMBLY

OK

5.	CHECK FOR DTC

(a) Check if SFI system DTCs are output.

Click here

Powertrain > Engine > Trouble Codes

Result	Proceed to
SFI system DTCs are not output.	A
SFI system DTCs are output.	B

B

GO TO SFI SYSTEM

A

6.	READ VALUE USING TECHSTREAM (ENGINE SPEED, ENGINE RPM)

(a) Connect the Techstream to the DLC3.

(b) Turn the engine switch on (IG).

(c) Turn the Techstream on.

(d) Enter the following menus:

(1) for Engine: Powertrain / Engine / Data List.

(2) for Combination Meter: Body Electrical / Combination Meter / Data List.

(e) Read the Data List according to the display on the Techstream.

(1) Engine

Powertrain > Engine > Data List

Tester Display	Measurement Item	Range	Normal Condition	Diagnostic Note
Engine Speed	Engine speed	Min.: 0 rpm, Max.: 16383 rpm	650 to 750 rpm: Idling (shift lever in N, engine warmed up and A/C off)	When the crankshaft position sensor is malfunctioning, "Engine Speed" is approximately 0 rpm or varies greatly from the actual engine speed.

Powertrain > Engine > Data List

Tester Display
Engine Speed

(2) Combination Meter

Body Electrical > Combination Meter > Data List

Tester Display	Measurement Item	Range	Normal Condition	Diagnostic Note
Engine Rpm	Engine speed	Min.: 0 rpm, Max.: 12750 rpm	Almost the same as actual tachometer	-

Body Electrical > Combination Meter > Data List

Tester Display
Engine Rpm

Result	Proceed to
The Data List values of the ECUs do not match.	A
The Data List values of the ECUs match.	B

B

REPLACE ECM

A

7.	REPLACE COMBINATION METER ASSEMBLY

(a) Replace the combination meter assembly with a new one.

Click here

OK:

The operation of the tachometer returns to normal.

OK

END

NG

REPLACE ECM