C1776

SUSPENSION CONTROL: AIR SUSPENSION SYSTEM: C1776/76: Speed Sensor Circuit

DTC C1776/76 - Speed Sensor Circuit

DTC C1794/94 - Front Speed Sensor RH Circuit Malfunction

DTC C1795/95 - Front Speed Sensor LH Circuit Malfunction

DESCRIPTION

The speed sensor detects the wheel speed and transmits the appropriate vehicle speed signal to the suspension control ECU through the skid control ECU.





HINT: When DTC C1794/94 and C1795/95 are output, follow the same procedure as DTC1776/76.

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 DATA LIST
(a) Connect the Techstream to DLC3.
(b) Turn the ignition switch ON and the Techstream on.
(c) Select the item "Vehicle Speed" in the Data List, and read its value displayed on the Techstream.
(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.

OK -- REPLACE SUSPENSION CONTROL ECU

NG -- Continue to next step.

2. CHECK DTC (VSC SYSTEM)
(a) Check if the normal code is output by VSC Vehicle Stability Control System.

NG -- REPAIR CIRCUIT INDICATED BY OUTPUT DTC
OK -- Continue to next step.

3. CHECK HARNESS AND CONNECTOR (SUSPENSION CONTROL ECU - SKID CONTROL ECU)
(a) Check for open and short circuit in the harness and the connector between the suspension control ECU and the skid control ECU Electronic Circuit Inspection Procedure.

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

4. INSPECT SUSPENSION CONTROL ECU (FLO SIGNAL, FRO SIGNAL)




(a) Remove the suspension control ECU with connector still connected.
(b) Turn the ignition switch ON.
(c) Connect an oscilloscope to between terminals S15-8 (FLO) and S15-1 (GND) and between terminals S15-9 (FRO) and S15-1 (GND) of the suspension control ECU harness side connector.




(d) Drive the vehicle with about 20 km/h (12 mph), and check the signal waveform.
OK:
Signal waveform appears as shown in the illustration.

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

NG -- REPLACE SUSPENSION CONTROL ECU
OK -- REPLACE SKID CONTROL ECU