Speed Signal Circuit

METER: METER / GAUGE SYSTEM: Speed Signal Circuit
- Speed Signal Circuit

DESCRIPTION

The meter CPU receives vehicle speed signals from this circuit. The vehicle speed sensor detects the voltage that varies according to the vehicle speed. The skid control ECU supplies power to the vehicle speed sensor. The skid control ECU detects vehicle speed signals based on the pulses of the voltage. The skid control ECU transmits vehicle speed signals as pulses to the meter CPU. A voltage of 12 V is output from the combination meter assembly and then input to the skid control ECU. The signal is changed to a pulse signal at the transistor in the combination meter assembly.

A voltage of 12 V or 5 V is output from each ECU or relay and then input to the combination meter assembly.

Each ECU controls the respective system based on the pulse signal.

HINT
This circuit is used for another system, and is not used for combination meter operation.

WIRING DIAGRAM





INSPECTION PROCEDURE

PROCEDURE

1. INSPECT COMBINATION METER ASSEMBLY (OUTPUT WAVEFORM)

(a) Remove the combination meter assembly, but do not disconnect the connector.





(b) Connect an oscilloscope to terminal F1-17 (+S) and the body ground.

(c) Shift the transmission gear selector lever to the neutral position.

(d) Jack up the vehicle.

(e) Turn the ignition switch on.

(f) Turn the wheel slowly.

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





OK:

The waveform is displayed as shown in the illustration.

HINT
As the vehicle speed increases, the cycle of the waveform narrows.

NG -- INSPECT COMBINATION METER ASSEMBLY (INPUT VOLTAGE)

OK -- RETURN TO THE ORIGINAL INSPECTION FOR OTHER SYSTEM

2. INSPECT COMBINATION METER ASSEMBLY (INPUT VOLTAGE)

(a) Disconnect the F1 combination meter assembly connector.





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

Standard voltage:





HINT
If any of the ECUs specified in the wiring diagram supplied power to the combination meter, the combination meter will output a waveform.

(c) Reconnect the combination meter assembly connector.

NG -- CHECK HARNESS AND CONNECTOR (COMBINATION METER ASSEMBLY - MAIN BODY ECU)
OK -- Continue to next step.

3. INSPECT COMBINATION METER ASSEMBLY (OUTPUT VOLTAGE)

(a) Disconnect the A15 ABS and traction actuator (skid control ECU) connector.





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

Standard voltage:





(c) Reconnect the ABS and traction actuator (skid control ECU) connector.

NG -- CHECK HARNESS AND CONNECTOR (COMBINATION METER ASSEMBLY - SKID CONTROL ECU)
OK -- Continue to next step.

4. INSPECT COMBINATION METER ASSEMBLY (INPUT WAVEFORM)

(a) Reconnect the A15 ABS and traction actuator (skid control ECU) connector.





(b) Remove the combination meter assembly, but do not disconnected the connector.

(c) Connect an oscilloscope to terminal F1-18 (SI) and the body ground.

(d) Shift the transmission gear selector lever to the neutral position.

(e) Jack up the vehicle.

(f) Turn the ignition switch on.

(g) Turn the wheel slowly.

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





OK:

The waveform is displayed as shown in the illustration.

HINT
As the vehicle speed increases, the cycle of the waveform narrows.

NG -- REPLACE ABS AND TRACTION ACTUATOR (SKID CONTROL ECU) Removal

OK -- REPLACE COMBINATION METER ASSEMBLY Removal

5. CHECK HARNESS AND CONNECTOR (COMBINATION METER ASSEMBLY - MAIN BODY ECU)

(a) Disconnect the 4C main body ECU connector.





(b) Disconnect the F1 combination meter assembly connector.

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

Standard resistance:





(d) Reconnect the main body ECU connector.

(e) Reconnect the combination meter assembly connector.

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

6. CHECK HARNESS AND CONNECTOR (COMBINATION METER ASSEMBLY - MALFUNCTIONING ECU)





(a) Disconnect the F1 combination meter assembly connector.

(b) Disconnect the A21 ECM connector, F12 radio receiver connector or F26 tire pressure warning ECU connector.

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

Standard resistance:





(d) Reconnect the combination meter assembly connector.

(e) Reconnect the ECM connector, the radio receiver connector or the tire pressure warning ECU connector.

NG -- CHECK HARNESS AND CONNECTOR (MAIN BODY ECU - MALFUNCTIONING ECU)

OK -- REPLACE MALFUNCTIONING ECU

7. CHECK HARNESS AND CONNECTOR (MAIN BODY ECU - MALFUNCTIONING ECU)

(a) Disconnect the 4B, 4C or 4D main body ECU connector(s).





(b) Disconnect the A21 ECM connector, the F12 radio receiver connector or F26 tire pressure warning ECU connector.

(c) Measure the resistance according to the values in the table below.

Standard resistance:





(d) Reconnect the main body ECU connector.

(e) Reconnect the ECM connector, the radio receiver connector or the tire pressure warning ECU connector.

NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR

OK -- REPLACE MAIN BODY ECU

8. CHECK HARNESS AND CONNECTOR (COMBINATION METER ASSEMBLY - SKID CONTROL ECU)

(a) Disconnect the F1 combination meter assembly connector.





(b) Disconnect the A15 ABS and traction actuator (skid control ECU) connector.

(c) Measure the resistance according to the values in the table below.

Standard resistance:





(d) Reconnect the combination meter assembly connector.

(e) Reconnect the ABS and traction actuator (skid control ECU) connector.

NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR

OK -- REPLACE COMBINATION METER ASSEMBLY Removal