Vehicle Speed Signal System A/T

DTC 12: Vehicle Speed Signal System

Vehicle Speed Signal System Circuit:

CIRCUIT OPERATION
This circuit checks the vehicle speed signal. When the vehicle moves forward and reverses, the sensor turns ON and OFF repeatedly.

DTC SET CONDITIONS
The vehicle speed signals from the PCM are not input to the auto-cruise control-ECU when the vehicle speed is 40 km/h (25 mph) or more.

TROUBLESHOOTING HINTS
The most likely causes for this code to be set are:
- Malfunction of the output shaft speed sensor.
- Damaged harness or connector.
- Malfunction of the PCM.
- Malfunction of the auto-cruise control-ECU.

DIAGNOSIS

Required Special Tool:
- MB991223: Harness Set

STEP 1. Check the speedometer.

Q: Does the speedometer work normally?

YES: Go to Step 2.

NO: Check the speedometer circuit and repair or replace as required. (Refer to Combination Meter Assembly and Vehicle Speed Sensor.)

STEP 2. Check joint connector (1) C-77.

Q: Is the connector damaged?

YES: Repair or replace connector. Refer to Harness Connector Inspection. Then check that diagnostic trouble code 12 is not output.

NO: Go to Step 3.

STEP 3. Check the harness wire between auto-cruise control-ECU connector C-20 (terminal number 10) and joint connector (1) C-77 (terminal number 19).

Q: Is any harness wire between auto-cruise control-ECU connector C-20 (terminal number 10) and joint connector (1) C-77 (terminal number 19) damaged?

YES: Repair the harness wire and then check that diagnostic trouble code 12 is not output.

NO: Check that diagnostic trouble code 12 is not output. If diagnostic trouble code 12 is output, replace the auto-cruise control-ECU. Then check that diagnostic trouble code 12 is not output.