797 and 797B Off-Highway Truck Caterpillar

Illustration 1	g00570894
(1) Transmission shift lever position sensor.

The position sensor for the transmission shift lever is located in the cab in the shift console.

Illustration 2	g00570895
Schematic Of The Position Sensor (Transmission Shift Lever)

The shift lever switch is used in order to control the desired top gear that is selected by the operator. The switch inputs for the shift lever consist of six wires. Five of the six wires provide codes to the chassis ECM. Each code is unique for each position of the shift lever switch. For each switch position of the shift lever, two of the five wires will send a ground signal to the chassis ECM. The other three wires remain open. The pair of grounded wires is unique to each position of the shift lever. The sixth wire is the ground verify wire, which is normally grounded. The ground verify wire is used to verify that the shift lever switch is connected to the chassis ECM.

This diagnostic code is recorded when the ECM reads erratic data from the position sensor.

Note: In order to view the switch positions of the shift lever, use the VIMS message center module or the status screen of the ET service tool and observe the “Gear Lever” status. As the shift lever is moved through the detent positions, the gear status should display the corresponding lever position that is shown on the shift console.

The possible causes of this diagnostic code are listed:

• Wire 113-OR(Orange), 711-BR(Brown), 712-WH(White), 713-OR(Orange), 714-YL(Yellow), 715-GN(Green) or 716-BU(Blue) are open or shorted to ground between the ECM and the transmission shift lever switch.

• The wire J897-GN(Green) between the transmission shift lever switch and frame ground is open.

• The transmission shift lever switch has failed.

• The ECM has failed.

Note: Ensure that the CID 0702 FMI 02 is active.

System Response:

Information for the gear selector is not available. The start control function is NOT available. The backup alarm function is disabled. The machine will NOT shift gears.

Test Step 1. CHECK FOR GROUND.

1. Remove the cover in order to expose the shift lever switch.

2. Remove the two bolts that fasten the switch to the transmission control housing.

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

4. Disconnect the machine harness from the switch.

5. Disconnect the machine harness connector J1 from the ECM.

6. At the machine harness connector for the switch, measure the resistance between contact 2 (J897-GN(Green)) and frame ground.

Expected Result:

The resistance that is measured is less than 5 ohms.

Results:

• OK - The resistance that is measured is less than 5 ohms. The harness is correct. Proceed to Test Step 2.

• NOT OK - The resistance that is measured is greater than 5000 ohms. The return wire has failed.

  Repair: Repair the machine harness or replace the machine harness.

  STOP

Test Step 2. CHECK THE POWER SUPPLY.

Note: The switch must be receiving +battery voltage at the connector contact 6 (wire 113-OR(Orange)).

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

2. At the machine harness connector for the transmission shift lever switch, measure the voltage from connector contact 6 to frame ground.

Expected Result:

The voltage that is measured is approximately +battery.

Results:

• OK - The voltage that is measured is approximately +battery. Proceed to Test Step 3.

• NOT OK - The voltage that is measured is NOT correct.

  Repair: Check wire 113-OR(Orange) in the machine harness for an open or short. Repair the machine harness or replace the machine harness.

  STOP

Test Step 3. CHECK FOR A HARNESS SHORT TO GROUND OR AN OPEN CIRCUIT.

1. Use the ET in order to view the status of the shift lever sensor.

Expected Result:

All of the wires are working properly.

Results:

• OK - All of the wires are working properly.

  STOP

• NOT OK - All of the wires are NOT working properly.

  Repair: Repair the machine harness or replace the machine harness.

  STOP