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Home >> Scion >> 2012 >> iQ L4-1.3L (1NR-FE) >> Repair and Diagnosis >> Instrument Panel, Gauges and Warning Indicators >> Testing and Inspection >> Component Tests and General Diagnostics >> Speed Signal Circuit

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*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 operation. Combination meter assembly components such as the speedometer operate using data received via CAN communication.

WIRING DIAGRAM





INSPECTION PROCEDURE

PROCEDURE

1. INSPECT COMBINATION METER ASSEMBLY (INPUT VOLTAGE)

(a) Disconnect the D1 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.

(c) Reconnect the combination meter assembly connector.

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

2. INSPECT COMBINATION METER ASSEMBLY (OUTPUT VOLTAGE)

(a) Disconnect the A16 brake actuator assembly (skid control ECU) connector.





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

Standard Voltage:





Text in Illustration





(c) Reconnect the brake actuator assembly (skid control ECU) connector.

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

3. INSPECT BRAKE ACTUATOR ASSEMBLY (INPUT WAVEFORM)

(a) Check the input waveform.





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

(2) Connect an oscilloscope to terminal D1-17 (SI) and body ground.

(3) Turn the ignition switch to ON.

(4) Turn the wheel slowly.

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





OK:

The waveform is displayed as shown in the illustration.

HINT
As the vehicle speed increases, the cycle of the waveform narrows.

Text in Illustration





NG -- REPLACE BRAKE ACTUATOR ASSEMBLY Removal

OK -- REPLACE COMBINATION METER ASSEMBLY Removal

4. CHECK HARNESS AND CONNECTOR (COMBINATION METER ASSEMBLY - BRAKE ACTUATOR ASSEMBLY)

(a) Disconnect the D1 combination meter assembly connector.

(b) Disconnect the A16 brake actuator assembly (skid control ECU) connector.

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

Standard Resistance:





(d) Reconnect the combination meter assembly connector.

(e) Reconnect the brake actuator assembly (skid control ECU) connector.

NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR

OK -- REPLACE COMBINATION METER ASSEMBLY Removal

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

(a) Disconnect the D68 junction block connector.

(b) Disconnect the D1 combination meter assembly connector.

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

Standard Resistance:





(d) Reconnect the junction block connector.

(e) Reconnect the combination meter assembly connector.

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

6. INSPECT ECM

(a) Disconnect the D68 junction block connector.





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

Standard Voltage:





Text in Illustration





(c) Reconnect the junction block connector.

NG -- CHECK HARNESS AND CONNECTOR (JUNCTION BLOCK - ECM)
OK -- Continue to next step.

7. INSPECT TIRE PRESSURE WARNING ECU

(a) Disconnect the D68 junction block connector.





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

Standard Voltage:





Text in Illustration





(c) Reconnect the junction block connector.

NG -- CHECK HARNESS AND CONNECTOR (JUNCTION BLOCK - TIRE PRESSURE WARNING ECU)
OK -- Continue to next step.

8. INSPECT RADIO RECEIVER ASSEMBLY

(a) Disconnect the D68 junction block connector.





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

Standard Voltage:





Text in Illustration





NG -- CHECK HARNESS AND CONNECTOR (JUNCTION BLOCK - RADIO RECEIVER ASSEMBLY)

OK -- REPLACE JUNCTION BLOCK

9. CHECK HARNESS AND CONNECTOR (JUNCTION BLOCK - ECM)

(a) Disconnect the D68 junction block connector.

(b) Disconnect the A18 ECM connector.

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

Standard Resistance:





(d) Reconnect the junction block connector.

(e) Reconnect the ECM connector.

NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR

OK -- REPLACE ECM Removal

10. CHECK HARNESS AND CONNECTOR (JUNCTION BLOCK - TIRE PRESSURE WARNING ECU)

(a) Disconnect the D68 junction block connector.

(b) Disconnect the D89 tire pressure warning ECU connector.

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

Standard Resistance:





(d) Reconnect the junction block connector.

(e) Reconnect the tire pressure warning ECU connector.

NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR

OK -- REPLACE TIRE PRESSURE WARNING ECU Removal

11. CHECK HARNESS AND CONNECTOR (JUNCTION BLOCK - RADIO RECEIVER ASSEMBLY)

(a) Disconnect the D68 junction block connector.

(b) Disconnect the D63 radio receiver assembly connector.

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

Standard Resistance:





(d) Reconnect the junction block connector.

(e) Reconnect the radio receiver assembly connector.

NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR

OK -- REPLACE RADIO RECEIVER ASSEMBLY
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