The following procedure is used to troubleshoot the auto/manual switch. The ECM does not diagnose problems with the auto/manual switch. However, the ECM is always watching the status of the input (contact 3) for the auto/manual switch. The input has two states: +battery and ground.
When the switch is NOT ACTIVATED, the switch contacts are open. The input to the ECM is at 0 VDC. When the switch is ACTIVATED, the switch contacts close. The input to the ECM is + battery voltage.
The possible causes of a problem with the auto/manual switch are listed.
- The +battery input to the switch (wire 123-WH) is not correct.
- The machine harness has failed.
- The auto/manual switch has failed.
- The ECM has failed. This is unlikely.
Test Step 1. CHECK THE +BATTERY INPUT TO THE ECM
- Turn the key start switch to the ON position.
- At the + battery input to the auto/manual switch (terminal 2), measure the voltage to ground.
Expected Result:
The voltage should measure +battery.
Results:
- OK - The voltage is +battery. The wiring (123-WH) is correct. Proceed to test step 2.
- NOT OK - The voltage is NOT +battery. The wiring (123-WH) is NOT correct.
Repair: Repair wire 123-WH or replace wire 123-WH.
Stop.
Test Step 2. CHECK THE CIRCUIT OPERATION AT THE ECM
- Turn the key start switch to the OFF position.
- Disconnect the machine harness from the ECM.
- At the machine harness connector, measure the resistance from contact 3 to contact 2 (ground).
- Observe the measurement while you activate the auto/manual switch and you deactivate the auto/manual switch.
Expected Result:
When the switch is ACTIVATED, the resistance should measure less than 5 ohms. When the switch is NOT ACTIVATED, the resistance should measure more than 5000 ohms.
Results:
- OK - The resistance is within an acceptable range. The circuit is functioning correctly. Proceed to test step 4.
- NOT OK - The resistance is not within an acceptable range. The switch has failed or the machine harness has failed. Proceed to test step 3.
Test Step 3. CHECK THE AUTO/MANUAL SWITCH
- Turn the key start switch to the OFF position.
- Disconnect the wire 973-BR from the auto/manual switch.
- Measure the resistance between the two terminals of the switch.
- Observe the measurement while you activate the auto/manual switch and you deactivate the auto/manual switch.
Expected Result:
When the switch is ACTIVATED, the resistance should measure less than 5 ohms. When the switch is NOT ACTIVATED, the resistance should measure more than 5000 ohms.
Results:
- OK - The resistance is within an acceptable range. The auto/manual switch is functioning correctly. The machine harness is faulty.
Repair: Repair the machine harness or replace the machine harness.
Stop.
- NOT OK - The resistance is not within an acceptable range. The switch has failed.
Repair: Repair the switch or replace the switch.
Stop.
Test Step 4. VERIFY PROPER OPERATION OF THE CIRCUIT
- Remove the connector from the ECM. Inspect the contacts and clean the contacts of the harness connectors.
- Reconnect all harness connectors.
- Test the operation of the auto/manual switch.
Expected Result:
The auto/manual switch operates correctly.
Results:
- NO - The auto/manual switch does NOT operate correctly.
Repair: The problem has not been corrected. It is unlikely that the ECM has failed. Perform the previous Step again. If the cause of the problem is not found, replace the ECM. See Testing and Adjusting, "Electronic Control Module (ECM) - Replace".
Stop.
- YES - The auto/manual switch operates correctly.
Repair: The problem does not exist at this time. The initial problem was probably caused by a poor electrical connection or a short at one of the harness connectors that was disconnected and reconnected. Resume normal machine operation.
Stop.