3126E On-highway Engine Caterpillar

Use this procedure under the following situation:

Use this procedure to determine if the circuit for the PTO Engine RPM Set Speed Input A and Input B is operating correctly.

The following background information is related to this procedure:

The ECM can use various inputs in a number of ways. The inputs depend on the parameter programming. Certain features are available on several different inputs. The configuration for the switch must match the actual switch installation in order for the switch to function properly.

PTO Engine RPM Set Speed Input A

The switch for the PTO Engine RPM Set Speed Input A controls the engine speed during PTO operation. The "PTO Engine RPM Set Speed A" parameter requires an engine RPM to be programmed. The "PTO Engine RPM Set Speed A" parameter is located in the "Dedicated PTO Parameter Group". The "PTO Engine RPM Set Speed Input A" status is also located in the "Input Selections Parameter Group". The engine will ramp up to the engine rpm that is programmed under the following conditions:

• The switch for the PTO Engine RPM Set Speed Input A is in the ON position and the PTO On/Off switch is then turned on.

• The switch for the PTO Engine RPM Set Speed Input A is turned to the ON position when the PTO On/Off switch is on.

The "PTO Configuration" must be programmed to "Cab Switches", "Remote Switches", or "Remote Throttle" for this feature to function. The PTO On/Off switch or the switch for the PTO Engine RPM Set Speed Input A must be cycled from the OFF position to the ON position in order to return to the programmed engine rpm if the PTO operation is disabled. If the "PTO Engine RPM Set Speed Input A" parameter is programmed to "None" (default), this feature is not used. If the "PTO Engine RPM Set Speed Input A" parameter is programmed to "J1/P1:46", the feature is available. Also, the switch circuit should be connected to the same input.

Switch for the PTO Engine RPM Set Speed Input B

The switch for the PTO Engine RPM Set Speed Input B is used to control engine RPM during PTO operation. The "PTO Engine RPM Set Speed B" parameter requires an engine RPM to be programmed. The "PTO Engine RPM Set Speed B" parameter is located in the "Dedicated PTO Parameter Group". The "PTO Engine RPM Set Speed Input B" status is located in the "Input Selections Parameter Group". The function of the switch for the PTO Engine RPM Set Speed Input B is similar to the function of the switch for the PTO Engine RPM Set Speed Input A. The engine will operate at set speed A when both of the switches are on. If the "PTO Engine RPM Set Speed Input B" parameter is programmed to "None" (default), this feature is not used. If the "PTO Engine RPM Set Speed Input B" parameter is programmed to "J1/P1:7" or "J1/P1:23", then the feature is available. Also, the switch circuit should be connected to the same input that is selected in the parameter.

Note: The wiring for your particular application may be slightly different. The circuits for the sensor common are used interchangeably by the OEM of the vehicle. The following circuits are common within the ECM:

• Terminal 18 (sensor common 1)

• Terminal 3 (sensor common 2)

• Terminal 5 (AP sensor/switch common)

Illustration 1	g00863820
Circuit schematic for the PTO Engine RPM Set Speed Input A switch circuit

Illustration 2	g00863819
Circuit schematic for the PTO Engine RPM Set Speed Input B switch circuit

Illustration 3	g00863993
Terminal locations for ECM connector P1

Test Step 1. Inspect Electrical Connectors and Wiring

1. Thoroughly inspect the ECM vehicle harness connector J1/P1, the connectors, and the firewall bulkhead connectors. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

2. Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the suspect switch circuit.

3. Check the ECM connector (allen head screw) for the proper torque of 6.0 N·m (55 lb in).

4. Check the harness and the wiring for abrasion and pinch points from the battery to the ECM. Then, check from the ignition key switch to the ECM.

   Refer to Illustration 3 for terminal locations for the ECM.

Expected Result:

All connectors, pins, and sockets are 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 wiring and connectors or replace the wiring or the connectors. Ensure that all of the seals are properly connected.Verify that the repair eliminates the problem.

  STOP

Test Step 2. Use Cat ET to Check the Status of the PTO Engine RPM Set Speed Input A and PTO Engine RPM Set Speed Input B

1. Connect the Caterpillar Electronic Technician ( Cat ET) to the cab data link connector.

2. Turn the ignition key switch to the ON position.

3. Operate the switch in the ON and OFF positions.

4. View the switch status on Cat ET.

5. If the "PTO Engine RPM Set Speed Input A" status indicates "Not Installed", then the parameter has not been programmed. If the "PTO Engine RPM Set Speed Input B" status indicates "Not Installed", then the parameter has not been programmed.

Expected Result:

The status screen should indicate "ON" if the switch is turned on. The status screen should indicate "OFF" if the switch is off.

Results:

• OK - The switch is operating normally. Continue troubleshooting if the original condition is not resolved.STOP

• Not OK - The ECM is not reading the switch status change. Proceed to Test Step 3.

Test Step 3. Check the Switch Circuit for the ECM

Illustration 4	g00864044
Connector for the breakout T

1. Turn the ignition key switch to the OFF position.

2. Install a breakout T to the ECM vehicle harness connector J1/P1.

3. Fabricate a jumper wire 100 mm (4 inch) long. Crimp a Deutsch pin to both ends of the wire.

4. Insert the jumper wire into the suspect switch socket of the breakout T. Connect the other end of the jumper wire to terminal 5 (AP Sensor/Switch Common) in the breakout T.

5. Connect Cat ET to the cab data link connector.

6. Turn the ignition key switch to the ON position.

7. Alternately remove the jumper wire and then insert the jumper wire from terminal 5. At the same time, monitor the status screen on Cat ET.

Expected Result:

The switch status changes to "ON" with the jumper wire in place. The switch status changes to "OFF" when the jumper wire is removed.

Results:

• OK - The ECM is functioning properly at this time. Proceed to Test Step 4.

• Not OK - The ECM is not functioning properly.

  Repair: Perform the following repair:

  1. Temporarily connect a test ECM. Only connect ECM harness J1/P1.

  2. Recheck for an +5 V diagnostic code when the engine harness is disconnected.

  3. If the problem is resolved with the test ECM, reconnect the suspect ECM.

  4. If the problem returns with the suspect ECM, replace the ECM.

  STOP

Test Step 4. Insert a Jumper Wire at the Switch

1. Turn the ignition key switch to the OFF position.

2. Reconnect the ECM vehicle harness connector J1/P1.

3. Fabricate a jumper wire 100 mm (4 inch) long. Crimp a Deutsch pin to both ends of the wire.

4. Insert the jumper wire between the two switch terminals.

5. Turn the ignition key switch to the ON position.

6. Alternately remove the jumper wire and then insert the jumper wire at the switch terminals. At the same time, watch the status screen on Cat ET.

Expected Result:

The switch status changes to "ON" with the jumper wire in place. The switch status changes to "OFF" when the jumper wire is removed.

Results:

• OK -

  Repair: Perform the following diagnostic procedure:Replace the switch. Verify that the repair eliminates the problem.

  STOP

• Not OK - There is a problem in the wire harness between the switch and the ECM. Proceed to Test Step 5.

Test Step 5. Insert a Jumper Wire at the Bulkhead Connector

1. Turn the ignition key switch to the OFF position.

2. Fabricate a jumper wire 100 mm (4 inch) long. Crimp a Deutsch pin to both ends of the wire.

3. Locate the suspect switch socket in the engine side of the bulkhead connector.

4. Insert the wire jumper pin between the switch socket and the sensor common connection. Install the jumper wire on the engine side of the bulkhead connector.

5. Turn the ignition key switch to the ON position.

6. Alternately connect and then disconnect the jumper wire. At the same time, monitor the status screen on Cat ET.

Expected Result:

The switch status changes from "ON" with the jumper wire in place. The switch status changes to "OFF" when the jumper wire is removed.

Results:

• OK - The problem is in the vehicle wiring between the bulkhead connector and the switch. Inspect the vehicle wiring and then repair the vehicle wiring. Otherwise, send the vehicle to the OEM dealer for repair. Verify that the original condition is resolved.STOP

• Not OK - The problem is in the vehicle wiring between the bulkhead connector and the ECM. Inspect the vehicle wiring and then repair the vehicle wiring. Otherwise, send the vehicle to the OEM dealer for repair. Verify that the original condition is resolved. STOP