Tachometer Malfunction

METER / GAUGE / DISPLAY: METER / GAUGE SYSTEM: Tachometer Malfunction
- Tachometer Malfunction

DESCRIPTION

The meter CPU receives engine speed signals from the ECM in this circuit. The ECM transmits engine speed signals as pulses to the meter CPU. The meter CPU calculates the engine speed converting 4 pulses to 2 revolutions.

WIRING DIAGRAM





INSPECTION PROCEDURE

PROCEDURE

1. PERFORM ACTIVE TEST USING TECHSTREAM (TACHO METER 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) Check the operation by referring to the values in the table below.

Combination Meter





OK:

Tachometer indication is normal.

NG -- REPLACE COMBINATION METER Removal
OK -- Continue to next step.

2. READ VALUE USING TECHSTREAM (ENGINE RPM)

(a) Connect the Techstream to the DLC3.

(b) Engine start.

(c) Turn the Techstream on.

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

(e) Check the values by referring to the values in the table below.

Combination Meter





Result:





C -- CHECK HARNESS AND CONNECTOR (COMBINATION METER - ECM)

B -- READ VALUE USING TECHSTREAM (ENGINE SPEED)

A -- REPLACE COMBINATION METER Removal

3. READ VALUE USING TECHSTREAM (ENGINE SPEED)

(a) Connect the Techstream to the DLC3.

(b) Engine start.

(c) Turn the Techstream on.

(d) Enter the following menus: Powertrain / Engine and ECT / Data List.

(e) Check the values by referring to the table below.

Engine and ECT





OK:

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

NG -- GO TO SFI SYSTEM (for 2UR-GSE) SFI System
OK -- Continue to next step.

4. CHECK HARNESS AND CONNECTOR (COMBINATION METER - ECM)

(a) Disconnect the A5 and J34 connectors.





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

Standard Resistance:





NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.

5. INSPECT ECM (INPUT WAVEFORM)

(a) Check the input signal waveform.





(1) Reconnect the A5 ECM connector.

(2) Connect the oscilloscope to the terminal J34-16 (S) and body ground.

(3) Start the engine.

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





OK:

The waveform is displayed as shown in the illustration.

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

NG -- REPLACE ECM (for 2UR-GSE) Removal

OK -- REPLACE COMBINATION METER Removal