System Operation Description:
Use this procedure under the following situation:
Use the following information in order to determine if the PTO Switch On Lamp is operating incorrectly.
Terminal 30 (Output 1)
With software that is older than OCT99, J1:30 (Output 1) is dedicated for use as a PTO Switch ON Lamp Output. If the “PTO Configuration” is programmed to Cab switches, Remote Switches, or Remote Throttle, the Output will turn the lamp ON whenever the PTO Switch Circuit is turned ON.
With OCT99 and newer software, J1:30 (Output 1) can be used as an output for the PTO Switch ON Lamp or as an output for the Low Coolant Level Warning Lamp. The parameters should be programmed to match the desired usage of the terminal. If the “Engine Monitoring Lamps” parameter is programmed to Warning Lamp, then output 1 is used for the PTO Switch ON Lamp. If the “Engine Monitoring Lamps” parameter is programmed to Option 1 and the “Coolant Level Lamp” parameter is programmed to “4-Pin” or “2 wire Float Sensor”, then output 1 is used for the low coolant level warning.
Note: The “PTO Configuration” must be programmed to Cab Switches, Remote Switches, or Remote Throttle to utilize the PTO Switch ON Lamp. Option 1 is not available for the GM truck manufacturer.
Electrical Connection of Lamps
One terminal of the lamp must be connected to battery voltage through the vehicle wiring. The other terminal is connected to the ECM at terminal J1/P1:30.
The ECM provides a path to ground in order to turn on the lamp.
Test Step 1. Inspect Electrical Connectors and Wiring
A. Thoroughly inspect ECM connector J1/P1, the firewall bulkhead connector, or the PTO Switch On Lamp. Refer to Troubleshooting, “Electrical Connectors – Inspect” for details.
B. Perform a 45 N (10 lb) pull test on each of the wires in the ECM Connector that are associated with the PTO Switch On Lamp.
Refer to Illustration 156.
C. Check the ECM connector (allen head screw) for the proper torque of 6.0 N·m (55 lb in).
D. Check the harness and wiring for abrasion and pinch points from the battery to the ECM.
Expected Result:
All connectors, pins and sockets should be completely coupled and/or inserted and the harness and wiring should be free of corrosion, abrasion or 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.
STOP.
Test Step 2. Check for Normal Operation of the PTO Switch On Lamp
A. Use the following procedure for the output 1 (PTO Switch On Lamp).
Connect the electronic service tool to the data link connector. Access the status screen that displays the “PTO Configuration” and the PTO On/Off Switch. The “PTO Configuration” must indicate “Cab Switches”, “Remote Switches”, or “Remote Throttle”. The “PTO Configuration” is not programmed to turn on the PTO Switch On Lamp if the “PTO Configuration” parameter is programmed to “OFF”.
While the PTO Switch On Lamp and the status of PTO On/Off Switch is being monitored on the electronic service tool, turn the PTO On/Off Switch to the ON position and the OFF position. The PTO Switch On Lamp should turn on when the PTO On/Off Switch is in the ON position. Also, the PTO Switch On Lamp should turn off when the PTO On/Off switch is in the OFF position.
Expected Result:
The lamp turns on and the lamp turns off per the above description.
Results:
• Yes – The lamp appears to operating correctly at this time. STOP.
• No – Proceed to Test Step 3.
Test Step 3. Test the Circuit for the PTO Switch On Lamp
A. Disconnect ECM connector J1/P1.
B. Fabricate a jumper wire 100 mm (4 inch) long.
Crimp a Deutsch pin to both ends of the wire.
C. Insert the jumper into P1:30 output 1.
D. Connect the other end of the jumper wire to one of the following terminal connections:.
• P1:63 ?battery
• P1:65 -battery
• P1/67 -battery
• P1:69 -battery
E. Turn the ignition key switch to the ON position.
F. While the lamp is being watched, insert the jumper wire and remove the jumper wire.
Refer to Illustration 157.
Expected Result:
Result 1 The PTO Switch On Lamp turns on while the jumper is connected to both sockets. Also, the PTO Switch On Lamp turns off when the jumper is removed from one of the sockets.
Result 2 The suspect lamp does not turn on while the jumper is connected to both sockets.
Result 3 The lamp will stay on while the ECM connector is disconnected.
Results:
• Result 1 – The circuit for the PTO Switch On Lamp is functioning properly. Proceed to Test Step 4.
• Result 2 – The lamp did not turn on. The vehicle’s lamp circuit is not functioning properly. The lamp is probably burned out or there is a problem in the wiring from the cab to either the ECM or the +Battery connection. Repair the lamp circuit or send the vehicle to the OEM dealer for repairs.
STOP.
• Result 3
Repair: Perform the following diagnostic
procedure:
The circuit between the ECM and the lamp is shorted to chassis ground. Repair the circuit or send the vehicle to the OEM dealer for repairs.
STOP.
Test Step 4. Use the Special Test “PTO Switch On Lamp” on the Electronic Service Tool to Check the Operation of the ECM
A. Disconnect ECM connector J1/P1.
B. Insert a breakout T between ECM connector J1 and ECM connector P1.
C. Connect one probe of the voltage test lamp to terminal 63 (-battery). Connect the other probe of the voltage test lamp to terminal 48 (un switched +battery) of the breakout T.
D. The test lamp should turn on. If the test lamp does not turn on, either the test lamp is faulty or the wiring to the ECM is faulty. Continue with this step if the lamp turns ON.
Note: Use the same procedure to check the following:
• P1:65 and P1:52
• P1:67 and P1:53
• P1:69 and P1:55
E. Leave the probe of the test lamp connected to terminal 48 (un switched +battery).
F. Connect the other probe of the test lamp to terminal 30 (Output 1) of the breakout T.
Refer to Illustration 158.
G. Connect the electronic service tool. Access the following display screens in order:
• “Diagnostics”
• “Diagnostic Test”
• “Special Test”
H. Activate the special test for the PTO Switch On Lamp. Observe the voltage test lamp. The lamp should turn on when the test is active. Also, the lamp should turn off when the test is inactive.
Note: Perform the same test procedure with terminals P1:52, P1:53, and P1:55 un switched +batt.
Expected Result:
The test lamp turns on and the test lamp turns off per the above description.
Results:
• Yes – The ECM is operating correctly. There is a problem in the vehicle wiring or the lamp. STOP.
• No
Repair: Temporarily connect a test ECM. Ensure that the “PTO Configuration” of the test ECM matches the “PTO Configuration” of the suspect ECM. Check the ECM output for the PTO Switch On Lamp when the test ECM is installed. If the problem is resolved with the test ECM, reconnect the suspect ECM. If the problem returns with the suspect ECM, replace the ECM. Refer to Troubleshooting, “Replacing the ECM”.
STOP.
