C1785

SUSPENSION CONTROL: AIR SUSPENSION SYSTEM: C1776/76,C1784/84,C1785/85: Speed Sensor Circuit

DTC C1776/76 - Speed Sensor Circuit

DTC C1784/84 - Right Rear Speed Sensor Circuit

DTC C1785/85 - Left Rear Speed Sensor Circuit

DESCRIPTION

The speed sensor monitors the speed of a wheel, and sends an appropriate speed signal to the suspension control ECU through the brake actuator assembly (skid control ECU).
If trouble occurs in the either right rear speed sensor or left rear speed sensor, the DTC (C1776/76) is output. When inspecting by test mode, the suspension control ECU scans changes of the signals. If there is no change, it outputs the test DTC (C1784/84, C1785/85).





HINT: When DTC C1784/84 and C1785/85 are output, follow the same procedure as DTC C1776/76.

WIRING DIAGRAM





INSPECTION PROCEDURE
HINT: Start the inspection from step 1 when using the Techstream, and start from step 2 when not using the Techstream.

PROCEDURE

1. READ VALUE USING TECHSTREAM
(a) Connect the Techstream to the DLC3.
(b) Turn the ignition switch to the ON position, and push the Techstream main switch on.
(c) Select the item below in the DATA LIST, and read its value displayed on the Techstream.
Air suspension:





(d) Check that there is no difference between the speed value output from the speed sensor displayed on the Techstream and the speed value displayed on the speedometer when driving the vehicle.
OK:
There is almost no difference in the displayed speed values.
HINT: There is tolerance of +- 10 % in the speedometer indication.

NG -- CHECK CIRCUIT INDICATED BY OUTPUT CODE
OK -- REPLACE SUSPENSION CONTROL ECU
2. CHECK CIRCUIT INDICATED BY OUTPUT CODE
(a) Check if the normal code is output by VSC system Reading and Clearing Diagnostic Trouble Codes.
OK:
No DTC output from VSC system.
NG -- REPAIR DTC OUTPUT
OK -- Continue to next step.
3. CHECK HARNESS AND CONNECTOR (SUSPENSION CONTROL ECU - BRAKE ACTUATOR ASSEMBLY)




(a) Disconnect the suspension control ECU S16 connector.
(b) Disconnect the brake actuator assembly S1 connector.
(c) Measure the resistance according to the values in the table below.
Standard resistance:






NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.
4. INSPECT SUSPENSION CONTROL ECU




(a) Connect the suspension control ECU S16 connector.
(b) Remove the suspension control ECU with connector being connected.
(c) Connect the brake actuator assembly S1 connector.
(d) Turn the ignition switch to the ON position.
(e) Check output waveform.
(1) Using an oscilloscope, connect the terminals, as shown in the chart.










(2) Drive the vehicle at about 20 km/h (12 mph), and check the output waveform.
OK:
The output waveform appears as shown in the illustration.





HINT: As the vehicle speed becomes higher, the waveform cycle gets shorter.

NG -- REPLACE BRAKE ACTUATOR ASSEMBLY
OK -- REPLACE SUSPENSION CONTROL ECU