TH220B, TH330B, TH340B, TH350B, TH355B, TH360B, TH460B, TH560B and TH580B Telehandlers Caterpillar

Illustration 1	g00904637

This diagnostic code is recorded when the ECM reads the voltage of the transmission neutralizer switch (wire G757-PU) as being below normal for three minutes continuously while the machine is in operation.

The possible causes of this diagnostic code are listed:

• The switch has failed.

• Wire G757-PU is shorted to ground between the switch and the ECM J2-58.

• The ECM has failed. This is unlikely.

System Response:

The transmission is placed in the neutral position.

Test Step 1. CHECK THE SWITCH.

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

2. Ensure that the diagnostic code is active.

3. Disconnect the switch from the machine harness.

4. Install a jumper wire between the signal wire (G757-PU) and the return wire (J764-BR) at the pressure switch.

Expected Result:

The diagnostic code changes from being active to being NOT active as the jumper is installed and the jumper wire is removed.

Note: The jumper needs to be installed for at least 3 minutes before a code is generated or the status can be checked immediately with the Electronic Technician (ET).

Results:

• OK - The diagnostic code is active. Then, the diagnostic code is NOT active as the jumper wire is installed and the jumper wire is removed. The pressure switch has failed.

  Repair: Repeat this test "CHECK THE SWITCH" in order to verify that the switch has failed. Replace the service brake pressure switch.

  Stop.

• NOT OK - The diagnostic code remains active. The diagnostic code does NOT change. The machine harness has failed or the ECM has failed. Proceed to test step 2.

Test Step 2. CHECK FOR A SHORT TO GROUND.

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

2. Remove all jumper wires that were previously installed.

3. Disconnect the J1 and J2 machine harness connectors from the ECM.

4. At the J1 machine harness connector for the ECM, measure the resistance from the signal contact J2-58 (wire G757-PU) to all possible sources of ground.

Expected Result:

The resistance for each measurement should be greater than 5000 ohms.

Results:

• OK - Each resistance measurement is greater than 5000 ohms. The harness is correct. The pressure switch has failed.

  Repair: Replace the pressure switch and verify that the new pressure switch corrects the problem. If the diagnostic code remains exit this procedure. It is unlikely that the ECM has failed. Perform this diagnostic code procedure again. If the cause of the diagnostic code is not found, replace the ECM. See Testing and Adjusting, "Electronic Control Module (ECM) - Replace".

  Stop.

• NOT OK - Each resistance measurement is NOT greater than 5000 ohms. The machine harness has failed.

  Repair: There is a short in the machine harness. The short is between the signal wire (G757-PU) and the wire with the low resistance measurement. Repair the machine harness or replace the machine harness.

  Stop.