Toyota Yaris: Meter / Gauge System / Speed Signal Circuit

DESCRIPTION

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. In addition, for some systems, vehicle speed information may be received via CAN communication.

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 (brake actuator assembly) which uses this information to create the vehicle speed signal. The vehicle speed signal is output from the skid control ECU (brake actuator assembly) to the certification ECU (smart key ECU assembly) and then to the combination meter assembly. To create this signal, 12 V is output from terminal SI of the combination meter assembly to the certification ECU (smart key ECU assembly). The pulse signal is created by switching the transistor in the certification ECU (smart key ECU assembly) 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 certification ECU (smart key ECU assembly). 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 this pulse signal.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

PROCEDURE

(a) Check for entry and start system (for start function) DTCs.

B

GO TO ENTRY AND START SYSTEM (FOR START FUNCTION)

A

(a) Disconnect the H6 combination meter assembly connector.

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

Standard Voltage:

NG

GO TO STEP 6

OK

(a) Disconnect the H46 certification ECU (smart key ECU assembly) connector.

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

Standard Voltage:

NG

GO TO STEP 5

OK

(a) Connect the H46 certification ECU (smart key ECU assembly) connector.

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

Click here

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

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.

OK

REPLACE COMBINATION METER ASSEMBLY

NG

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

(a) Disconnect the H6 combination meter assembly connector.

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

Standard Resistance:

OK

REPLACE COMBINATION METER ASSEMBLY

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

(a) Disconnect the H6 combination meter assembly connector.

(b) Disconnect the A106 ECM connector.

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

Standard Resistance:

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

(a) Disconnect the H6 combination meter assembly connector.

(b) Disconnect the A106 ECM connector.

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

Standard Voltage:

HINT:

If the result is as specified, there may be a short circuit in the ECM.

OK

REPLACE ECM

NG

REPLACE COMBINATION METER ASSEMBLY