Inspection Procedure 6

TECHNICAL DESCRIPTION (COMMENT)
The cause is probably the malfunction of the vehicle speed sensor or incorrect vacuum in the auto-cruise control vacuum pump or actuator.

TROUBLESHOOTING HINTS
- Malfunction of the vehicle speed sensor.
- Malfunction of the auto-cruise control vacuum pump.
- Malfunction of the actuator.
- Malfunction of the auto-cruise control-ECU.

DIAGNOSIS

Required Special Tool:
- MB991223: Harness Set




STEP 1.Check the vehicle speed sensor.
1. Remove the vehicle speed sensor and connect a 3 - 10 kOhms resistor as shown in the illustration.
2. Turn the shaft of the vehicle speed sensor and check that there is voltage between terminals 2 - 3.(one turn = four pulses)

Q: Is the voltage within specifications?

YES: Go to Step 2.

NO: Replace the vehicle speed sensor.
Refer to Combination Meter Assembly and Vehicle Speed Sensor.
Then check that the malfunction is eliminated.

STEP 2.Check the auto-cruise vacuum pump.
1. Disconnect the vacuum hose from the auto-cruise vacuum pump and connect a vacuum gauge to the vacuum pump.
2. Disconnect the vacuum pump connector.




3. Check the auto-cruise vacuum pump and valves according to the following procedure:
- Connect the positive battery terminal to auto-cruise vacuum pump connector terminal 1, and the negative battery terminal to terminals 2, 3, and 4.
Then the vacuum gauge should read 27 kPa (8.0 in Hg) or more.
- The vacuum should be maintained when terminal 4 is disconnected from the negative battery terminal while terminals 1, 2, and 3 remain connected.
Then the vacuum gauge should read 0 kPa (0 in Hg) when terminal 2 is disconnected from the negative battery terminal while terminals 1, and 3 remain connected.
- The vacuum should be maintained when terminal 4 is disconnected from the negative battery terminal while terminals 1, 2, and 3 remain connected. Then the vacuum gauge should read 0 kPa (0 in Hg) when terminal 3 is disconnected from the negative battery terminal while terminals 1, and 2 remain connected.

Q: Are all of the above values satisfied?

YES: Go to Step 3.

NO: Replace the auto-cruise vacuum pump.
Then that the malfunction is eliminated.




STEP 3.Check the vacuum actuator.
1. Disconnect the vacuum hose from the vacuum actuator, and then connect a hand vacuum pump to the vacuum actuator.
2. Apply a vacuum and check that the throttle lever moves and the vacuum is maintained.

Q: Is the vacuum actuator damaged?

YES: Replace the vacuum actuator.
For 2.4L Engine, refer to Throttle Body Assembly.
For 3.0L Engine, refer to Throttle Body Assembly.
Then check that the malfunction is eliminated.

NO: Check that the malfunction is eliminated.
If the malfunction is eliminated, replace the auto-cruise control-ECU.
Then check that the malfunction is eliminated.