Tachometer Malfunction

METER: 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 3 pulses to 1 revolution.

WIRING DIAGRAM





INSPECTION PROCEDURE

PROCEDURE

1. PERFORM ACTIVE TEST USING TECHSTREAM (TACHO METER OPERATION)
(a) Connect the Techstream to the DLC3.
(b) Turn the ignition switch to the ON position.
(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:
Needle indication is normal.
NG -- REPLACE COMBINATION METER ASSEMBLY
OK -- Continue to next step.
2. READ VALUE USING TECHSTREAM (ENGINE RPM)
(a) Connect the Techstream to the DLC3.
(b) Turn the ignition switch to the ON position.
(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 SIGNAL)
A -- REPLACE COMBINATION METER ASSEMBLY
3. READ VALUE USING TECHSTREAM (ENGINE SPEED SIGNAL)
(a) Connect the Techstream to the DLC3.
(b) Turn the ignition switch to the ON position.
(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 tester is almost the same as the actual engine speed.
NG -- GO TO SFI SYSTEM
OK -- Continue to next step.
4. CHECK HARNESS AND CONNECTOR (COMBINATION METER - ECM)




(a) Disconnect the C8 and E6 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) Remove the combination meter with the connector still connected.
(2) Connect the oscilloscope to terminal C8-7 (TACH) 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.
NG -- REPLACE ECM
OK -- REPLACE COMBINATION METER ASSEMBLY