STEM AS 1104214 - Caterpillar

System Operation Description:Use this procedure under the following situation:Use this procedure to determine if the neutral switch is operating properly.Automatic Transmission Neutral SwitchThe automatic transmission neutral switch is required when the "Transmission Style" parameter is programmed to "Automatic Option 3", "Automatic Option 4", "AT/MT/HT Option 3", or "AT/MT/HT Option 4". This switch is used to indicate when the automatic transmission is in neutral.The automatic transmission neutral switch is an open circuit when the transmission is in gear. Shifting the transmission to the neutral position should close the circuit, which connects the input to the battery voltage. Many other switches in the system connect the input to ground when the circuit is closed.This switch may not be connected to an input on the ECM. The parameter "Transmission Neutral Switch" determines the input to the ECM. If the parameter is programmed to "J1/P1:62" a switch must be connected to terminal 62. If the parameter is programmed to "J1939", the switch position will be transmitted to the ECM over the J1939 data link. If a problem is suspected with the J1939 data link, refer to Troubleshooting, "Powertrain Data Link Circuit - Test".
Illustration 1 g00646460
Schematic for transmission neutral switch
Test Step 1. Inspect Electrical Connectors and Wiring
Illustration 2 g01151850
Pin locations on ECM connector
(P1-62) Input 12 (transmission neutral switch)
Thoroughly inspect ECM vehicle harness connector J1/P1, the firewall bulkhead connector and the terminals for the following switches in the connectors:
Neutral switch (P1-62)Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the switches. Refer to Illustration 2.
Check the ECM connector (allen head screw) for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
Check the harness and wiring for abrasion and pinch points from the sensor to the ECM. Expected Result:All connectors, pins and sockets are completely coupled and/or inserted and the harness and wiring are free of corrosion, of abrasion or of pinch points.Results:
OK - Proceed to Test Step 2.
Not OK - Repair: Repair the connectors or wiring and/or replace the connectors or wiring. Ensure that all of the seals are properly in place and ensure that the connectors are completely coupled.Verify that the repair eliminates the problem.STOPTest Step 2. Check Neutral Switch Status on Caterpillar Electronic Technician (ET)
Table 1
Status of the Neutral Switch
Switch Position Switch Status Circuit
The transmission is in Neutral. ON Closed
The transmission is in Gear. OFF Open
Connect Cat ET to the cab data link connector.
Access the status screen on Cat ET.
Turn the ignition key switch to the ON position.
Shift the transmission into the Neutral position while the status of the neutral switch is being observed. Also, shift out of Neutral while the status of the neutral switch is being observed. Note: If the status indicates "Not Installed", check the programming of the "Transmission Style" Parameter. The "Transmission Style" must be programmed to "Automatic Option 3" or "Automatic Option 4".Expected Result:The switch status changes per the information in Table 1.Results:
Yes - The switch