C15 – Ignore Brake/Clutch Switch Circuit – Test

System Operation Description:
Use this procedure under the following situation:
The circuit for the Ignore Brake/Clutch Switch is suspected of incorrect operation.

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.

Ignore Brake/Clutch Switch

The ignore brake/clutch switch is typically used with a “Cab Switches PTO Configuration” which requires mobile use of the vehicle during PTO operation. When the ignore brake/clutch switch is on, depressing the brake or the clutch will not disengage PTO operation or a set engine speed. If the “Ignore/Brake Clutch Switch” parameter is programmed to “None” (default), this feature is not used. If the “Ignore/Brake Clutch Switch” parameter is programmed to J1/P1:47, then the feature is available and the switch circuit should be connected to terminal 47 of the J1/P1 ECM vehicle harness connector.

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:

• The “Input Sensor Common 1” is terminal 18.
• The “Input Sensor Common 2” is terminal 3.
• The “AP Sensor/Switch Sensor Common” is terminal 5.

Test Step 1. Check the Electrical Connectors and the Wiring

A. Thoroughly inspect the ECM vehicle harness connector J1/P1, the connectors, and the firewall bulkhead connectors. 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 circuit for the “Ignore Brake/Clutch Switch”.

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 the wiring for abrasion and pinch points from the ignore brake/clutch switch to the ECM.
Refer to Illustration 108 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 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. Check the Status of the Ignore Brake/Clutch Switch on ET

A. Connect the Caterpillar Electronic Technician (ET) at the cab data link connector.

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

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

D. View the “Ignore Brake/Clutch Switch” status on ET.

E. If the “Ignore Brake/Clutch Switch” status indicates “Not Installed”, then the “Ignore Brake/Clutch Switch” 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 turned 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 change in switch status. Proceed to Test Step 3.

Test Step 3. Check the Switch Circuit at the ECM

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

B. Install a 70 terminal breakout T to the ECM vehicle harness connector J1/P1.

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

D. Insert the jumper wire into terminal 18 (Input Sensor Common #1) of the breakout T. Insert the other end of the jumper wire into terminal 47 (Ignore Brake/Clutch Switch) of the breakout T.

E. Connect ET to the cab data link connector.

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

G. Alternately remove the jumper wire and insert the jumper wire at terminal 18 while you monitor the status screen on ET.

Expected Result:
The switch status changes from “ON” with the jumper wire in place 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.
2. Remove all jumpers and replace all connectors.
3. Recheck the system for active diagnostic codes.
4. Repeat the Test Step.
5. If the problem is resolved with the test ECM, reconnect the suspect ECM.
6. If the problem returns with the suspect ECM, replace the ECM.
7. Verify that the repair eliminates the problem.
STOP.

Test Step 4. Insert a Jumper Wire at the Switch
A. Turn the ignition key switch to the OFF position.

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

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

D. Insert the jumper wire between the two terminals of the ignore brake/clutch switch.

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

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

Expected Result:
The switch status changes to “ON” with the jumper wire in place to “OFF” when the jumper wire is removed.

Results:
• OK

Repair: Replace the ignore brake/clutch switch.

Verify that the repair eliminates the problem.

STOP.
• Not OK – There is a problem in the wire harness between the Ignore Brake/Clutch Switch and the ECM. Proceed to Test Step 5.

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

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

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

C. Insert the jumper wire between the two terminals for the ignore brake/clutch switch on the engine side of the ECM bulkhead connector.

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

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

Expected Result:
The switch status changes from “ON” with the jumper wire in place to “OFF” when the jumper wire is removed.

Results:
• OK – The problem is in the vehicle wiring between the bulkhead connector and the switch.

Repair: 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.

Repair: 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.

 

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