C7 Engine for AP-1000D, AP-1055D, BG-2455D, and BG-260D Asphalt Pavers Caterpillar

The Electronic Control Module (ECM) supplies a regulated voltage of 8.0 ± 0.4 VDC to the throttle switch.

This procedure covers the following diagnostic codes:

• 41-03 8 Volt DC Supply short to +batt

• 41-04 8 Volt DC Supply short to ground

A +8 V diagnostic code is probably caused by a short circuit to ground or a short circuit to another voltage source in the harness. The next likely cause is a problem with the throttle switch. The least likely cause is a problem with the ECM.

Illustration 1	g01208108
Schematic

Test Step 1. Inspect the Electrical Connectors and the Wiring

1. Remove the electrical power from the ECM.

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Illustration 2	g01208116
Left side view of the engine (1) J1/P1 ECM connectors

2. Thoroughly inspect connectors (1). Inspect the connectors for the throttle switch. Refer to diagnostic functional tests Troubleshooting, "Electrical Connectors - Inspect".

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Illustration 3	g01209336
P1 ECM connector (P1-22) High throttle input (P1-23) Low throttle input

3. Perform a 45 N (10 lb) pull test on each of the wires that are associated with the throttle switch.

4. Check the torque of the allen head screws for the ECM connectors. Refer to diagnostic functional tests Troubleshooting, "Electrical Connectors - Inspect".

5. Check the harness and wiring for abrasions and for pinch points from the throttle switch to the ECM.

Expected Result:

All of the 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 - The connectors and the wiring are OK. Proceed to Test Step 2.

• Not OK - There is a problem with a connector and/or the wiring.

  Repair: Repair the connector and/or the wiring. Replace parts, if necessary. Ensure that all of the seals are properly in place and ensure that the connectors are completely coupled. Verify that the problem is resolved.

  STOP

Test Step 2. Check for Active Diagnostic Codes

1. Connect the Caterpillar Electronic Technician (ET) to the service tool connector. Refer to electronic troubleshooting Troubleshooting, "Electronic Service Tools".

2. Restore the electrical power to the ECM.

3. Observe the active diagnostic code screen on Cat ET. Wait at least 30 seconds so that any codes may become active. Look for these codes:
   • 41-03

   • 41-04

Expected Result:

One of the above diagnostic codes is active.

Results:

• Active 41-03 code - A 41-03 diagnostic code is active. Proceed to Test Step 3.

• Active 41-04 code - A 41-04 diagnostic code is active. Proceed to Test Step 4.

• No active codes - None of the above codes are active.

  Repair: If any of the above codes are logged and the engine is not running properly, refer to troubleshooting without a diagnostic code Troubleshooting.If the engine is running properly at this time, there may be an intermittent problem in a harness that is causing the codes to be logged. Refer to diagnostic functional tests Troubleshooting, "Electrical Connectors - Inspect".

  STOP

Test Step 3. Check the Voltage on the +8 V Supply Wire

1. Remove the electrical power from the ECM.

2. Disconnect the harness connector for the throttle switch.

3. Restore the electrical power to the ECM.

4. Measure the voltage between the wires for the suspect throttle input(s) to wire A287-BK.

Expected Result:

The voltage measurement of the suspect throttle input(s) is 8.0 ± 0.4 VDC .

Results:

• OK - The voltage measurement of the suspect throttle input(s) is 8.0 ± 0.4 VDC.

  Repair: Connect the connectors for the throttle switch. Clear all diagnostic codes. Check for active diagnostic codes. If the problem is intermittent, refer to diagnostic functional tests Troubleshooting, "Electrical Connectors - Inspect".

  STOP

• Not OK - The voltage measurement for one of the suspect throttle input(s) is not 8.0 ± 0.4 VDC. There is a problem with the wiring or with the ECM. Proceed to Test Step 5.

Test Step 4. Disconnect the Throttle Switch and Check for Active Diagnostic Codes

1. Disconnect the harness connector for the throttle switch.

Note: Wait for 30 seconds after you disconnect the throttle switch for any affected code.

Expected Result:

The 41-04 diagnostic code deactivates when the throttle switch is disconnected.

Results:

• OK - The 41-04 diagnostic code deactivates when the throttle switch is disconnected.

  Repair: Connect the throttle switch. If the diagnostic code returns, replace the throttle switch.Connect the connectors for the throttle switch. Verify that the problem is resolved.

  STOP

• Not OK - The 41-04 diagnostic code remains after the throttle switch is disconnected. Leave the throttle switch disconnected. Proceed to Test Step 5.

Test Step 5. Check the +8 V Supply Wire for a Short Circuit

1. Remove the electrical power from the ECM.

2. Disconnect the J1/P1 and J2/P2 connectors.

3. Verify that the throttle switch is disconnected.

Note: Wiggle the harness during the following measurements in order to reveal an intermittent condition.

4. Measure the resistance between P1-22 (High throttle input) and the remaining terminals on the P1 and P2 connectors.

5. Measure the resistance between P1-22 (High throttle input) and the engine ground.

6. Measure the resistance between P1-23 (Low throttle input) and the remaining terminals on the P1 and P2 connectors.

7. Measure the resistance between P1-23 (Low throttle input) and the engine ground.

Expected Result:

Each check of the resistance indicates an open circuit.

Results:

• OK - Each check of the resistance indicates an open circuit. Proceed to Test Step 6.

• Not OK - At least one check of the resistance does not indicate an open circuit. A throttle input has a problem. There may be a problem with a connector.

  Repair: Repair the wire and/or the connector, when possible. Replace parts, if necessary. Verify that the problem is resolved.

  STOP

Test Step 6. Check the +8 V Supply and the Sensor Common for an Open Circuit

1. Install a jumper wire between terminals P1-22 (High throttle input) and P1-5 (Return).

Note: Wiggle the harness during the following measurement in order to reveal any intermittent short condition.

2. At the throttle switch, measure the resistance between the wire for the high throttle input and the wire A287-BK.

3. Remove the jumper wire.

4. Install a jumper wire between terminals P1-23 (Low throttle input) and P1-5 (Return).

Note: Wiggle the harness during the following measurement in order to reveal any intermittent short condition.

5. At the throttle switch, measure the resistance between the wire for the low throttle input and the wire A287-BK.

Expected Result:

The resistance measurement is less than ten Ohms.

Results:

• OK - The resistance measurements are less than ten Ohms. Proceed to Test Step 7.

• Not OK - One of the resistance measurements is more than ten Ohms. A throttle input wire or a return wire has excessive resistance. There may be a problem with a connector.

  Repair: Repair the wires and/or the connector, when possible. Replace parts, if necessary. Verify that the problem is resolved.

  STOP

Test Step 7. Check the +8 V Supply at the ECM

1. Remove terminal 22 from the P1 connector. Install a jumper wire with socket terminals on both ends into P1-22.

2. Remove terminal 23 from the P1 connector. Install a jumper wire with socket terminals on both ends into P1-23.

3. Remove terminal 5 from the P1 connector. Install a jumper wire with socket terminals on both ends into P1-5.

4. Connect the P1 connector.

5. Restore the electrical power to the ECM.

6. Measure the voltage between the jumper wires in P1-22 and P1-5.

7. Measure the voltage between the jumper wires in P1-23 and P1-5.

8. Remove the electrical power from the ECM.

9. Restore all wiring to the original configuration.

Expected Result:

The voltage measurements are 8.0 ± 0.4 VDC.

Results:

• OK - The voltage measurements are 8.0 ± 0.4 VDC.

  Repair: Clear all diagnostic codes. Check for active diagnostic codes. If the problem is intermittent, refer to diagnostic functional tests Troubleshooting, "Electrical Connectors - Inspect".

  STOP

• Not OK - One of the voltage measurement is not 8.0 ± 0.4 VDC.

  Repair: Replace the ECM. Refer to electronic troubleshooting Troubleshooting, "Replacing the ECM".

  STOP