Vehicle Speed Signal Circuit Between Radio Receiver and Combination Meter

AUDIO / VISUAL: AUDIO AND VISUAL SYSTEM: Vehicle Speed Signal Circuit between Radio Receiver and Combination Meter
- Vehicle Speed Signal Circuit between Radio Receiver and Combination Meter

DESCRIPTION

The circuit is necessary for the ASL (Automatic Sound Levelizer) built into the radio receiver assembly.

Speed signals are received from the combination meter assembly and used for the ASL. The ASL function automatically adjusts the sound volume in order to enable clear audio quality even when vehicle noise increases (as vehicle noise increases, the volume is turned up etc.).

HINT
* A voltage of 12 V or 5 V is output from each ECU and then input to the combination meter assembly. The signal is changed to a pulse signal at the transistor in the combination meter assembly. Each ECU controls its respective system based on the pulse signal.
* If a short occurs in any of the ECUs or in the wire harness connected to an ECU, all systems in the diagram below will not operate normally.

WIRING DIAGRAM





INSPECTION PROCEDURE

PROCEDURE

1. CHECK OPERATION OF SPEEDOMETER

(a) Drive the vehicle and check if the function of the speedometer on the combination meter is normal.

OK:

Actual vehicle speed and the speed indicated on the speedometer are the same.

HINT
* The speed indicated on the speedometer has an allowable margin of error. This can be tested using a speedometer tester (calibrated chassis dynamometer). For details about testing and the margin of error, refer to "On-Vehicle Inspection" in the meter/gauge system On-Vehicle inspection.
* The vehicle speed sensor is functioning normally when the indication on the speedometer is normal.

NG -- GO TO METER / GAUGE SYSTEM How To Proceed With Troubleshooting
OK -- Continue to next step.

2. INSPECT COMBINATION METER ASSEMBLY (SPEED SIGNAL)

(a) Disconnect the R3 radio receiver assembly connector.





(b) Jack up the drive wheels.

(c) Move the shift lever to N.

(d) Turn the ignition switch to ON.

(e) Using an oscilloscope, check the signal waveform of the meter.

Waveform





HINT
As the vehicle speed increases, the wavelength shortens.

OK:

Voltage pulses as shown in the illustration.

(f) Reconnect the radio receiver assembly connector.

NG -- CHECK HARNESS AND CONNECTOR (RADIO RECEIVER - COMBINATION METER ASSEMBLY)

OK -- REPLACE RADIO RECEIVER ASSEMBLY Removal

3. CHECK HARNESS AND CONNECTOR (RADIO RECEIVER - COMBINATION METER ASSEMBLY)

(a) Disconnect the R3 radio receiver connector.





(b) Disconnect the C9 combination meter assembly connector.

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

Standard Resistance:





HINT
If the resistance between terminal SPD and body ground is less than 10 kOhms, there may be a short in a wire harness, connector, or an ECU that is connected to the SPD signal wire.

(d) Reconnect the radio receiver assembly connector.

(e) Reconnect the combination meter assembly connector.

NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR

OK -- REPLACE COMBINATION METER ASSEMBLY Removal