IT28G and IT38G Integrated Toolcarriers and 924G, 924GZ, 928G and 938G Wheel Loaders Power Train Electronic Control System Caterpillar

Illustration 1	g00821347
Schematic of the Circuit for the Shift Lever

Note: Before troubleshooting the shift lever, move the shift lever through all positions. Check for any active diagnostic codes.

This procedure relates to the shift lever and to the components of the harness that are related to the shift lever. When measurements are taken, use the 146-4080 Digital Multimeter, or an equivalent Multimeter. Use the 7X-1708 Multimeter Probe. Connect the spoons to the positive lead and the negative lead. Check the related circuits for opens and shorts in the harness, and measure the resistance of the wire.

Reference the electrical schematic of the machine. The schematic is used in order to quickly locate the wiring that is related to the shift lever.

Test Step 1. CHECK FOR AN INTERMITTENT CONNECTION

Use the Electronic Technician (ET) when this test step is performed.

1. Connect the ET to the machine.

2. Turn the key start switch and the disconnect switch to the ON position.

3. Start the ET.

   Note: The ET will initiate communications with the Electronic Control Modules on the machine. After communication has been established, the ET will list the Electronic Control Modules on the machine.

4. Select the desired Electronic Control Module.

5. Select "diagnostics" from the main menu. Then, select "active diagnostics" from the drop-down menu.

6. Monitor the active diagnostic screen while each of the harnesses and the connectors that are connected to the component is wiggled.

   Note: If the harness wiggled and the diagnostic code disappears, there is a problem in the wiring or the connector.

7. From the Status screen, monitor the shift lever as the harnesses are wiggled.

   Note: If the harness is wiggled and the reading changes erratically, there is a problem in the wiring or the connector.

Expected Result:

Wiggling the harnesses or the connectors does NOT have an effect on the status of a diagnostic code or the operation of the shift lever.

Results:

• OK - Wiggling the harnesses or the connectors does NOT have an effect on the status of a diagnostic code or the operation of the shift lever. Proceed to test step 2.

• NOT OK - Wiggling the harnesses or the connectors has an effect on the status of a diagnostic code or the operation of the shift lever.

  Repair: Repair the harness and/or connectors or replace the harness and/or connectors that are causing the problem.

  Stop.

Test Step 2. INSPECT THE ELECTRICAL CONNECTORS.

1. Perform the "Electrical Connector - Inspect" procedure in this manual.

Expected Result:

Every test step in the "Electrical Connector - Inspect" procedure has an OK result.

Results:

• OK - Every test step in the "Electrical Connector - Inspect" procedure has an OK result. Proceed to test step 3.

• NOT OK - One of the test steps in the "Electrical Connector - Inspect" procedure has an NOT OK result.

  Repair: Follow the recommended repair that is provided in the "Electrical Connector - Inspect" procedure.

  Stop.

Test Step 3. CHECK THE DATE CODE OF THE SHIFT LEVER.

Some shift lever may experience any of the following failure modes:

• Intermittent operation of the speed function

• Disabling of the speed output (transmission neutralizer)

• Speed output remains in the last valid speed.

1. Check the shift lever for a suspect date code.

   Note: A problem is limited to certain dates of manufacturing for the shift lever. There is a date code with six Alpha-characters on the bottom of the shift lever. The last four characters of the suspect date codes are "NRNN", "NANN", "NLNN", "NKNN", "NONN", and "NDNN".

Expected Result:

The shift lever DOES NOT have a suspect date code.

Results:

• OK - The shift lever DOES NOT have a suspect date code. Follow the remaining Troubleshooting procedure if a problem exists with the shift lever. Additional service information will be announced as the information becomes available. Proceed to test step 4.

• NOT OK - The shift lever has a suspect date code.

  Repair: Replace the shift lever.

  Stop.

Test Step 4. CHECK THE SHIFT LEVER.

1. The ECM and the shift lever remain connected to the wiring harness.

2. The disconnect switch and the key start switch are in the ON position.

3. The remote direction switch is in the NEUTRAL position.

4. Place the shift lever is in the position with the problem, if known.

5. At the harness connector for the ECM, measure the voltages from contact 2 (wire 202-BK) to the following contacts at the shift lever:
   • Contacts 1 to 8 (8 Pin Connector)

   • Contacts 1,2, 5, and 6 (6 Pin Connector)

   • Contacts 1,2, and 3 (4 Pin Connector)

6. Compare the measurements with the following tables.
   Show/hide table

   Table 1

   FNR Switch	Shift Lever Pos.	Key Start Switch Pos.	1st Gear	2nd Gear	3rd Gear	4th Gear	Start Relay	Neut. Out	Rev Out	Fwd Out
   			1	2	3	4	5	6	7	8
   			8 Pin	8 Pin	8 Pin	8 Pin	8 Pin	8 Pin	8 Pin	8 Pin
   			VDC	VDC	VDC	VDC	VDC	VDC	VDC	VDC
   N	1F	Run	0.11	3.53	3.53	3.53	0.02	3.54	3.52	0.11
   N	2F	Run	3.53	0.11	3.53	3.53	0.02	3.54	3.51	0.11
   N	3F	Run	3.53	3.53	0.11	3.53	0.02	3.53	3.51	0.11
   N	4F	Run	3.53	3.53	3.53	0.11	0.02	3.54	3.51	0.11
   N	N	Run	0.11	3.51	3.51	3.51	27.05	0.11	3.49	3.51
   N	1R	Run	0.11	3.53	3.53	3.53	0.02	3.53	0.11	3.53
   N	2R	Run	3.53	0.11	3.53	3.53	0.02	3.53	0.11	3.53
   N	3R	Run	3.53	3.53	0.11	3.53	0.02	3.53	0.11	3.53

   Show/hide table

   Table 2

   FNR Switch	Shift Lever Pos.	Key Start Switch Pos.	+ Battery	Ground	Key Switch (In)	Backup Alarm (Out)
   			1	2	5	6
   			6 Pin	6 Pin	6 Pin	6 Pin
   			VDC	VDC	VDC	VDC
   N	1F	Run	27.99	0.02	27.94	27.94
   N	2F	Run	27.99	0.02	27.95	27.94
   N	3F	Run	27.99	0.02	27.94	27.94
   N	4F	Run	27.99	0.02	27.94	27.94
   N	N	Run	28.01	0.01	27.92	27.95
   N	1R	Run	27.97	0.03	27.93	0.63
   N	2R	Run	27.97	0.03	27.93	0.63
   N	3R	Run	27.97	0.03	27.93	0.63

   Show/hide table

   Table 3

   FNR Switch	Shift Lever Pos.	Key Start Switch Pos.	Fwd Switch In	Rev Switch In	Neutral Switch Input
   			1	2	3
   			4 Pin	4 Pin	4 Pin
   			VDC	VDC	VDC
   N	1F	Run	27.93	27.93	0.03
   N	2F	Run	27.93	27.93	0.02
   N	3F	Run	27.93	27.93	0.02
   N	4F	Run	27.93	27.93	0.02
   N	N	Run	27.94	27.94	0.03
   N	1R	Run	27.92	27.92	0.03
   N	2R	Run	27.92	27.92	0.03
   N	3R	Run	27.92	27.92	0.03

Expected Result:

The voltage that is measured is within the specification of ± 0.10 VDC. See the tables that are provided.

Results:

• OK - The voltage that is measured is within the specification of ± 0.10 VDC. Proceed to test step 5.

• NOT OK - One or more of the measured voltages are NOT within the specification. Inspect the wiring harness from the ECM to the shift lever. Check for damaged components or loose connections in the harness.

  Repair: Ensure that the fuse and the circuit breaker for the transmission controls are in the proper working condition. Inspect the ground strap for the ECM. Verify that the ground strap is secure and undamaged. There should be continuity in the wiring harness between the shift lever and the ECM for the power and ground circuits. Repair any failed components or replace any failed components with the recommended Caterpillar parts.

  Stop.

Test Step 5. CHECK THE WIRING HARNESS FOR SHORT CIRCUIT CONDITIONS.

1. Turn the key start switch and the disconnect switch to the OFF position.

2. Disconnect the ECM and the shift lever from the wiring harness.

3. At the harness connector for the ECM, measure the resistance from contact 20 (Wire G768-GN) to all other contacts.

4. At the harness connector for the ECM, measure the resistance from contact 21 (Wire G760-WH) to all other contacts.

5. At the harness connector for the ECM, measure the resistance from contact 22 (Wire G761-YL) to all other contacts.

6. At the harness connector for the ECM, measure the resistance from contact 23 (Wire G762-BR) to all other contacts.

7. At the harness connector for the ECM, measure the resistance from contact 10 (Wire G763-PU) to all other contacts.

8. At the harness connector for the ECM, measure the resistance from contact 17 (Wire G755-GY) to all other contacts.

9. At the harness connector for the ECM, measure the resistance from contact15 (Wire G750-BU) to all other contacts.

Expected Result:

The resistance for each measurement is greater than 5000 ohms.

Results:

• OK - The resistance for each measurement is greater than 5000 ohms. Proceed to test step 6.

• NOT OK - The resistance that is measured is less than 5 ohms for one or more of the measurements.

  Repair: Repair the wiring harness or replace the wiring harness.

  Stop.

Test Step 6. CHECK THE HARNESS FOR AN OPEN CIRCUIT.

Note: Measure the resistance of the appropriate wires. For example, the shift lever operates properly in every direction except the FIRST SPEED FORWARD position. Then, perform the appropriate test steps.

1. The key start switch and the disconnect switch remain in the OFF position.

2. The ECM and the shift lever remain disconnected from the wiring harness.

3. At the harness connector for the ECM, measure the resistance from contact 20 (Wire G768-GN) to contact 1 (Wire G768-GN) at the six pin connector for the shift lever.

4. At the harness connector for the ECM, measure the resistance from contact 21 (Wire G760-WH) to contact 2 (Wire G760-WH) at the six pin connector for the shift lever.

5. At the harness connector for the ECM, measure the resistance from contact 22 (Wire G761-YL) to contact 3 (Wire G761-YL) at the six pin connector for the shift lever.

6. At the harness connector for the ECM, measure the resistance from contact 23 (Wire G762-BR) to contact 4 (Wire G762-BR) at the six pin connector for the shift lever.

7. At the harness connector for the ECM, measure the resistance from contact 10 (Wire G763-PU) to contact 6 (Wire G763-PU) at the six pin connector for the shift lever.

8. At the harness connector for the ECM, measure the resistance from contact 17 (Wire G755-GY) to contact 7 (Wire G755-GY) at the eight pin connector for the shift lever.

9. At the harness connector for the ECM, measure the resistance from contact 15 (Wire G750-BU) to contact 8 (Wire G750-BU) at the eight pin connector for the shift lever.

Expected Result:

The resistance for each measurement is less than 5 ohms.

Results:

• OK - The resistance for each measurement is less than 5 ohms. Proceed to test step 7.

• NOT OK - The resistance for one or more of the measurements is greater than 5000 ohms. A problem exists in the harness.

  Repair: Repair the harness or replace the harness.

  Stop.

Test Step 7. VERIFY THAT THE SHIFT LEVER IS OPERATING CORRECTLY.

1. Connect the ECM and the shift lever to the wiring harness.

2. Turn the disconnect switch and the key start switch to the ON position.

3. Shift the transmission through every gear and shift the transmission through every direction position.

4. Check the shift lever for proper operation.

Expected Result:

The shift lever problem remains.

Results:

• YES - The shift lever problem remains. The condition has not been corrected. The transmission electronic control module may have failed. Proceed to test step 8.

• NO - The shift lever is operating correctly. The problem was probably caused by a poor electrical connection.

  Repair: Resume normal operation and watch for a reoccurence of the problem.

  Stop.

Test Step 8. VERIFY THAT THE TRANSMISSION ELECTRONIC CONTROL MODULE HAS FAILED.

1. Turn the key start switch and the disconnect switch to the OFF position.

2. Disconnect the shift lever from the wiring harness.

3. Create a jumper wire that can short from contact 2 on the six pin connector to two of the pins on the eight pin connector on the wiring harness.

4. Turn the disconnect switch and the key start switch to the ON position.

5. Use the ET to display "Group 1 Gear Lever Parameters".

6. Connect the jumper from pin 2 (6 pin connector) to pins 1 and 8 (8 pin connector). The gear lever should read "1" on the display.

7. Connect the jumper from pin 2 (6 pin connector) to pins 2 and 8 (8 pin connector). The gear lever should read "2" on the display.

8. Connect the jumper from pin 2 (6 pin connector) to pins 3 and 8 (8 pin connector). The gear lever should read "3" on the display.

9. Connect the jumper from pin 2 (6 pin connector) to pins 4 and 8 (8 pin connector). The gear lever should read "4" on the display.

10. Connect the jumper from pin 2 (6 pin connector) to pins 1 and 7 (8 pin connector). The gear lever should read "1R" on the display.

11. Connect the jumper from pin 2 (6 pin connector) to pins 2 and 7 (8 pin connector). The gear lever should read "2R" on the display.

12. Connect the jumper from pin 2 (6 pin connector) to pins 3 and 7 (8 pin connector). The gear lever should read "3R" on the display.

13. Connect the jumper from pin 2 (6 pin connector) to pins 4 and 7 (8 pin connector). The gear lever should read "4R" on the display.

14. Connect the jumper from pin 2 (6 pin connector) to pins 4 and 6 (8 pin connector). The gear lever should read "N" on the display.

Expected Result:

All of the gear parameters are correct.

Results:

• OK - All of the gear parameters are correct. The problem is due to a problem in either the wiring harness or the shift lever. Exit this procedure and perform this procedure again. Stop.

• NOT OK - All of the gear parameters are NOT correct. The ECM may have failed.

  Repair: It is unlikely that the ECM has failed. Exit this procedure and perform this procedure again. If the cause of the problem is not found, replace the ECM. Refer to Testing and Adjusting, "Electronic Control Module (ECM) - Replace".

  Stop.