Inspection Procedure 16

CIRCUIT OPERATION
When the system voltage from PCM (terminal number 75) is grounded at auto-cruise control ECU (terminal number 3), the auto-cruise control ECU emits a overdrive cancel signal.
When a malfunction of the auto-cruise circuit occurs, the transmission may downshift harshly with the auto-cruise engaged.

COMMENT
A malfunction may be present on the auto-cruise signal line circuit, auto-cruise control ECU or the PCM.

TROUBLESHOOTING HINTS
The most likely causes for this cause:
- Damaged connector
- Malfunction of the PCM
- Malfunction of the auto-cruise control ECU

DIAGNOSIS

STEP 1. Check the auto-cruise system.
Check the auto-cruise system. Refer to Auto-cruise Control System Diagnostic Troubleshooting Strategy.
If the auto-cruise system is operating properly, go to Step 2.
If the auto-cruise system is not operating properly, repair it, then check the symptom.

STEP 2. Check the auto-cruise sensor signal circuit.





1. Disconnect harness connector C-35 at auto-cruise control ECU.
2. Turn the ignition switch ON.
3. Measure the voltage between terminal 3 and ground.
- Voltage should be system voltage.
If system voltage, replace auto-cruise control ECU. Recheck the symptom. If symptom still exists, replace PCM.
If not system voltage, go to Step 3.

STEP 3. Check the harness connector C-91 at the PCM for damage.





If the harness connector C-91 is damaged, repair or replace it. Refer to Harness Connector Inspection. Then check the symptom.
If harness connector C-91 is in good condition, go to Step 4.

STEP 4. Check the harness connector C-35 at the auto-cruise control ECU for damage.





If the harness connector C-35 is damaged, repair or replace it. Refer to Harness Connector Inspection. Then check the symptom.
If harness connector C-35 is in good condition, go to Step 5.

STEP 5. Check the harness wire between PCM connector C-91 and auto-cruise control ECU connector C-35.





NOTE: After inspecting intermediate connector C-41, inspect the wire. If intermediate connector C-85 is damaged, repair or replace it. Refer to Harness Connector Inspection.





If any harness wire between PCM connector C-91 and auto-cruise control ECU connector C-35 is damaged, repair it. Refer to Harness Connector Inspection. Then check the symptom.
If the harness wire is in good condition, check the symptom.
If the symptom is not eliminated, replace the PCM.