Speed Signal Circuit

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

DESCRIPTION

The combination meter 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 from the skid control ECU. To create this signal, 12 V is output from IG2 which is behind a resistor in the combination meter. 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 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 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 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 operation. Combination meter components such as the speedometer operate using data received via CAN communication.

WIRING DIAGRAM

1. for 2AZ-FE

2. for 2ZR-FE

INSPECTION PROCEDURE

PROCEDURE

1. INSPECT ECU TERMINAL VOLTAGE (INPUT VOLTAGE)

(a) Disconnect the E55 connector.

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

Standard Voltage:

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

NG -- CHECK HARNESS AND CONNECTOR
OK -- Continue to next step.

2. INSPECT COMBINATION METER (OUTPUT VOLTAGE)

(a) Reconnect the E55 connector.

(b) Disconnect the A38 connector.

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

Standard Voltage:

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

3. INSPECT SKID CONTROL ECU (INPUT WAVEFORM)

(a) Check the input waveform.

(1) Reconnect the A38 connector.

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

(3) Connect the oscilloscope to terminal E55-35 (SI) and body ground.

(4) Turn the ignition switch to ON.

(5) Turn a drive wheel slowly.

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

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 Removal

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

(a) Disconnect the E55 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 COMBINATION METER ASSEMBLY Removal

5. CHECK HARNESS AND CONNECTOR

(a) Inspect for a short in the circuits connected to the combination meter 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 E55 and 2E and E32*1 and E44*2 connectors.

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

Standard Resistance:

* *1: w/ Radio Receiver

* *2: w/ Tire Pressure Warning System

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

6. CHECK TIRE PRESSURE WARNING ECU (OUTPUT VOLTAGE)

HINT
For vehicles not equipped with a tire pressure warning system, proceed to the next step.

(a) Reconnect the E44 connector.

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

Standard Resistance:

HINT
If the result is not as specified, there may be a short in the tire pressure warning ECU.

NG -- REPLACE TIRE PRESSURE WARNING ECU Removal
OK -- Continue to next step.

7. CHECK RADIO RECEIVER (OUTPUT VOLTAGE)

HINT
For vehicles not equipped with a radio receiver, proceed to the next step.

(a) Reconnect the E32 connector.

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

Standard Resistance:

HINT
If the result is not as specified, there may be a short in the radio receiver.

NG -- REPLACE RADIO RECEIVER Removal
OK -- Continue to next step.

8. CHECK DRIVER SIDE JUNCTION BLOCK ASSEMBLY

(a) Inspect for a short in the circuit that is connected to the combination meter 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 2C, 2D, and 2E connectors.

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

Standard Voltage:

*1: w/ Sliding Roof

Result:

B -- CHECK HARNESS AND CONNECTOR (ECM CIRCUIT)

C -- CHECK SLIDING ROOF CONTROL ECU (SLIDING ROOF CONTROL ECU CIRCUIT)

A -- REPLACE DRIVER SIDE JUNCTION BLOCK ASSEMBLY

9. CHECK HARNESS AND CONNECTOR (ECM CIRCUIT)

(a) Disconnect the A37 connector.

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

Standard Resistance:

Result:

* *1: for 2AZ-FE

* *2: for 2ZR-FE

B -- REPLACE ECM (for 2ZR-FE) Removal

C -- REPAIR OR REPLACE HARNESS OR CONNECTOR

A -- REPLACE ECM (for 2AZ-FE) Removal

10. CHECK SLIDING ROOF CONTROL ECU (SLIDING ROOF CONTROL ECU CIRCUIT)

HINT
For vehicles not equipped with a sliding roof, proceed to the next step.

(a) Reconnect the 2C, 2D, and 2E connectors.

(b) Disconnect the O2 connector.

HINT
If the speed signal circuit operates normally after disconnecting the sliding roof control ECU, there may be a short in the sliding roof control ECU.

NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR

OK -- REPLACE SLIDING ROOF CONTROL ECU Disassembly