Speed Signal Circuit

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

DESCRIPTION

The combination meter assembly (No. 3 meter circuit plate) 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*1. 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.

* *1: 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 (no. 3 meter circuit plate) operation. Combination meter assembly components such as the speedometer operate using data received via CAN communication.

WIRING DIAGRAM

INSPECTION PROCEDURE

PROCEDURE

1. INSPECT ECU TERMINAL VOLTAGE (INPUT VOLTAGE)

(a) Disconnect the L27 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 (NO. 3 METER CIRCUIT PLATE - RADIO AND DISPLAY RECEIVER ASSEMBLY, NAVIGATION ECU SUB-ASSEMBLY)
OK -- Continue to next step.

2. INSPECT COMBINATION METER ASSEMBLY (NO. 3 METER CIRCUIT PLATE) (OUTPUT VOLTAGE)

(a) Reconnect the L27 connector.

(b) Disconnect the A58 connector.

Text in Illustration

NG -- CHECK HARNESS AND CONNECTOR (NO. 3 METER CIRCUIT PLATE - SKID CONTROL ECU)
OK -- Continue to next step.

3. INSPECT SKID CONTROL ECU (INPUT WAVEFORM)

(a) Check the input waveform.

(1) Reconnect the A58 connector.

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

(3) Connect an oscilloscope to terminal L27-8 (SI) and body ground.

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

(5) Turn the wheel slowly.

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

Text in Illustration

OK:

The waveform is displayed as 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 SKID CONTROL ECU Removal

OK -- REPLACE COMBINATION METER ASSEMBLY (NO. 3 METER CIRCUIT PLATE) Disassembly

4. CHECK HARNESS AND CONNECTOR (NO. 3 METER CIRCUIT PLATE - SKID CONTROL ECU)

(a) Disconnect the L27 and A58 connectors.

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

Standard Resistance:

NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR

OK -- REPLACE COMBINATION METER ASSEMBLY (NO. 3 METER CIRCUIT PLATE) Disassembly

5. CHECK HARNESS AND CONNECTOR (NO. 3 METER CIRCUIT PLATE - RADIO AND DISPLAY RECEIVER ASSEMBLY, NAVIGATION ECU SUB-ASSEMBLY)

(a) Disconnect the L27 and L130*1 or L149*2 connectors.

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

Standard Resistance:

* *1: for Navigation Receiver Type or for Radio and Display Type (w/o Daytime Running Light)

* *2: for Radio and Display Type (w/ Daytime Running Light)

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

6. INSPECT RADIO AND DISPLAY RECEIVER ASSEMBLY, NAVIGATION ECU SUB-ASSEMBLY (OUTPUT VOLTAGE)

(a) Reconnect the L130*1 or L149*2 connector.

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

Standard Voltage:

* *1: for Navigation Receiver Type or for Radio and Display Type (w/o Daytime Running Light)

* *2: for Radio and Display Type (w/ Daytime Running Light)

Result:

B -- REPLACE RADIO AND DISPLAY RECEIVER ASSEMBLY Removal

C -- REPLACE NAVIGATION ECU SUB-ASSEMBLY
A -- Continue to next step.

7. INSPECT VEHICLE APPROACHING SPEAKER CONTROLLER ASSEMBLY (OUTPUT VOLTAGE)

(a) Reconnect the L140 connector.

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

Standard Voltage:

NG -- REPLACE VEHICLE APPROACHING SPEAKER CONTROLLER
OK -- Continue to next step.

8. CHECK HARNESS AND CONNECTOR (COMBINATION METER ASSEMBLY - NO. 3 JUNCTION BLOCK)

(a) Disconnect the 3A 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.

9. CHECK HARNESS AND CONNECTOR (NO. 3 JUNCTION BLOCK (INSTRUMENT PANEL WIRE))

(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 3B connector.

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

Standard Voltage:

Text in Illustration

Result:

B -- REPLACE NO. 3 JUNCTION BLOCK (INSTRUMENT PANEL WIRE)
A -- Continue to next step.

10. CHECK HARNESS AND CONNECTOR (NO. 3 JUNCTION BLOCK - NO. 4 JUNCTION BLOCK)

(a) Disconnect the 4A 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.

11. CHECK HARNESS AND CONNECTOR (NO. 4 JUNCTION BLOCK (INSTRUMENT PANEL WIRE))

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

Standard Voltage:

Text in Illustration

Result:

B -- REPLACE NO. 4 JUNCTION BLOCK (INSTRUMENT PANEL WIRE)
A -- Continue to next step.

12. SYSTEM CHECK

(a) Select the circuit for which voltage was not present in step 9 or 11.

Result:

* *1: w/ Tire Pressure Warning System

* *2: w/ Automatic Type Headlight Beam Level Control

* *3: w/ Manual (SOS) Switch

B -- CHECK HARNESS AND CONNECTOR (STEREO COMPONENT AMPLIFIER ASSEMBLY CIRCUIT)

C -- CHECK HARNESS AND CONNECTOR (TIRE PRESSURE WARNING ECU CIRCUIT)

D -- CHECK HARNESS AND CONNECTOR (HEADLIGHT LEVELING ECU CIRCUIT)

E -- CHECK HARNESS AND CONNECTOR (DCM (TELEMATICS TRANSCEIVER) CIRCUIT)
A -- Continue to next step.

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

(a) Disconnect the L5 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 Removal

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

(a) Disconnect the L143 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

15. CHECK HARNESS AND CONNECTOR (TIRE PRESSURE WARNING ECU CIRCUIT)

(a) Disconnect the L4 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 TIRE PRESSURE WARNING ECU Removal

16. CHECK HARNESS AND CONNECTOR (HEADLIGHT LEVELING ECU CIRCUIT)

(a) Disconnect the A48 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

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

(a) Disconnect the L144 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