Speed Signal Circuit

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

DESCRIPTION

The combination meter assembly receives the vehicle speed signal from this circuit. The wheel speed sensors produce an output that varies according to the vehicle speed. The wheel speed sensor output is received by the skid control ECU which uses this information to create the vehicle speed sensor signal*a. The vehicle speed sensor signal consists of pulses sent to the combination meter assembly from the skid control ECU. To create this signal, 12 V is output from IG2 which is behind a resistor in the combination meter assembly. This voltage is sent to the skid control ECU. The pulse signal is created by switching the transistor in the skid control ECU on and off, making the voltage on the wire drop to 0 V. A similar system is used for the output of this signal from the combination meter assembly via terminal +S. A voltage of 12 V or 5 V is applied to terminal +S from each ECU or relay that is connected to this terminal. The transistor in the combination meter assembly is controlled by the signal from the skid control ECU. When this transistor is turned on, this transistor makes the voltage supplied by the various ECUs (via their respective internal resistors) drop to 0 V. Each ECU connected to terminal +S of the combination meter assembly controls its respective system based on the pulse signal.

* *a: This vehicle speed sensor signal is created by the skid control ECU. There is no actual component that is referred to as the vehicle speed sensor. In addition, for some other systems, vehicle speed information may be exchanged using CAN communication.

HINT
This circuit is used for the systems connected to terminal +S. This signal is not used for combination meter assembly operation. Combination meter assembly components such as the speedometer operate using data received via CAN communication.

WIRING DIAGRAM

1. for 2AR-FXE

INSPECTION PROCEDURE

PROCEDURE

1. INSPECT ECU TERMINAL VOLTAGE (INPUT VOLTAGE)

(a) Disconnect the I18 combination meter assembly connector.

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

Standard Voltage:

Text in Illustration

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

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

2. INSPECT COMBINATION METER ASSEMBLY (OUTPUT VOLTAGE)

(a) Reconnect the I18 combination meter assembly connector.

(b) Disconnect the A28 skid control ECU connector.

Text in Illustration

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

3. INSPECT SKID CONTROL ECU (INPUT WAVEFORM)

(a) Check the input waveform.

(1) Reconnect the A49 skid control ECU connector.

(2) Remove the combination meter assembly with the connector(s) still connected.

(3) Connect an oscilloscope to terminal I18-8 (SI) and body ground.

(4) Turn the power switch on (IG).

(5) Turn a wheel slowly.

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

Text in Illustration

OK:

The waveform is similar to that shown in the illustration.

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

NG -- REPLACE BRAKE BOOSTER ASSEMBLY Removal

OK -- REPLACE COMBINATION METER ASSEMBLY Removal

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

(a) Disconnect the I18 combination meter assembly and A28 skid control ECU connector.

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

Standard Resistance:

NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR

OK -- REPLACE BRAKE BOOSTER ASSEMBLY Removal

5. CHECK HARNESS AND CONNECTOR (COMBINATION METER ASSEMBLY - JUNCTION CONNECTOR)

(a) Disconnect the I124 junction connector.

(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.

6. CHECK HARNESS AND CONNECTOR (JUNCTION CONNECTOR)

(a) Inspect for a short in the circuit that is connected to the junction block connector shown in the wiring diagram.

HINT
If voltage is not present, it is possible that an ECU or circuit has a malfunction. The malfunctioning ECU or circuit will be diagnosed in the following steps.

(1) Disconnect the I124 junction connector.

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

Standard Voltage:

Result:

B -- CHECK HARNESS AND CONNECTOR (DCM (TELEMATICS TRANSCEIVER) CIRCUIT)

C -- REPLACE JUNCTION CONNECTOR (INSTRUMENT PANEL WIRE)
A -- Continue to next step.

7. SYSTEM CHECK

(a) Select the circuit for which voltage was not present in step 6.

Result:

*1: for 10 Speakers

*2: for Radio Receiver Type

*3: for Radio and Display Type w/o Intuitive Parking Assist System

*4: for Radio and Display Type w/ Intuitive Parking Assist System

*5: for Navigation Receiver Type

*6: w/ Automatic Headlight Beam Level Control System

*7: w/ Vehicle Proximity Notification System

B -- CHECK HARNESS AND CONNECTOR (RADIO RECEIVER ASSEMBLY CIRCUIT, NAVIGATION ECU SUB-ASSEMBLY CIRCUIT, RADIO AND DISPLAY RECEIVER ASSEMBLY CIRCUIT)

C -- CHECK HARNESS AND CONNECTOR (HEADLIGHT LEVELING ECU ASSEMBLY CIRCUIT)

D -- CHECK HARNESS AND CONNECTOR (POWER MANAGEMENT CONTROL ECU ASSEMBLY CIRCUIT)

E -- CHECK HARNESS AND CONNECTOR (VEHICLE APPROACHING SPEAKER CONTROLLER CIRCUIT)
A -- Continue to next step.

8. CHECK HARNESS AND CONNECTOR (STEREO COMPONENT AMPLIFIER ASSEMBLY CIRCUIT)

(a) Disconnect the I69 stereo component amplifier assembly connector.

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

Standard Resistance:

NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR

OK -- REPLACE STEREO COMPONENT AMPLIFIER ASSEMBLY Removal

9. CHECK HARNESS AND CONNECTOR (RADIO RECEIVER ASSEMBLY CIRCUIT, NAVIGATION ECU SUB-ASSEMBLY CIRCUIT, RADIO AND DISPLAY RECEIVER ASSEMBLY CIRCUIT)

(a) Disconnect the I150 radio receiver assembly*1 or I67 navigation ECU sub-assembly*2, *3, or I155 radio and display receiver assembly*4

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

Standard Resistance:

*1: for Radio Receiver Type

*2: for Navigation Receiver Type

*3: for Radio and Display Type w/ Intuitive Parking Assist System

*4: for Radio and Display Type w/o Intuitive Parking Assist System

Result:

B -- REPLACE NAVIGATION RECEIVER ASSEMBLY Removal

C -- REPLACE RADIO AND DISPLAY RECEIVER ASSEMBLY Removal

D -- REPAIR OR REPLACE HARNESS OR CONNECTOR

A -- REPLACE RADIO RECEIVER ASSEMBLY Removal

10. CHECK HARNESS AND CONNECTOR (HEADLIGHT LEVELING ECU ASSEMBLY CIRCUIT)

(a) Disconnect the A34 headlight leveling ECU assembly connector.

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

Standard Resistance:

NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR

OK -- REPLACE HEADLIGHT LEVELING ECU ASSEMBLY Removal

11. CHECK HARNESS AND CONNECTOR (POWER MANAGEMENT CONTROL ECU ASSEMBLY CIRCUIT)

(a) Disconnect the I3 power management control ECU assembly connector.

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

Standard Resistance:

NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR

OK -- REPLACE POWER MANAGEMENT CONTROL ECU ASSEMBLY Removal

12. CHECK HARNESS AND CONNECTOR (VEHICLE APPROACHING SPEAKER CONTROLLER CIRCUIT)

(a) Disconnect the I71 vehicle approaching speaker controller connector.

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

Standard Resistance:

NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR

OK -- REPLACE VEHICLE APPROACHING SPEAKER CONTROLLER Removal

13. CHECK HARNESS AND CONNECTOR (DCM (TELEMATICS TRANSCEIVER) CIRCUIT)

(a) Disconnect the I135 DCM (telematics transceiver) connector.

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

Standard Resistance:

NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR

OK -- REPLACE DCM (TELEMATICS TRANSCEIVER) Removal