D6N Track-Type Tractor Caterpillar

Illustration 1	g01377182
Connections of the alternator

Illustration 2	g01895334
Location of the alternator

This code is recorded when the ECM reads the voltage at contact R is less than 24 V for 2 seconds.

Test Step 1. CHECK FOR POWER AT THE ECM.

1. Run the engine at high idle.

2. At the ECM, measure the voltage from contact J2-14 to ground.

Expected Result:

The voltage is greater than 24 V.

Results:

• YES - The voltage is greater than 24 DCV. Return the engine speed to idle. Proceed to Test Step 2.

• NO - The voltage is less than 24 DCV.

  Repair: The charging system is not correct or the harness is open. Check the charging system. See Systems Operation, SENR2947, "Starting and Charging System".

  STOP

Test Step 2. CHECK THE CABLE OF THE ALTERNATOR FOR A SHORT TO BATTERY.

1. Disconnect the harness cable J2 from the module.

2. Measure the resistance from the alternator input (403-GN) to + battery contact 1.

Expected Result:

The resistance should be greater than 5000 ohms.

Results:

• OK - The harness is correct. Proceed to Test Step 3.

• NOT OK - The harness cable has a short to the battery.

  Repair: Repair the cable. Verify that the diagnostic code is not active.

  STOP

Test Step 3. CHECK FOR AN ACTIVE DIAGNOSTIC CODE.

1. Measure the voltage at the battery posts.

Expected Result:

The voltage is greater than 24 V.

Results:

• YES - The voltage is greater than 24 DCV. Proceed to Test Step 4.

• NO - The voltage is less than 24 DCV.

  Repair: The charging system is not correct. Check the charging system. See Systems Operation, SENR2947, "Starting and Charging System".

  STOP

Test Step 4. CHECK THE VOLTAGE AT THE ALTERNATOR.

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

2. Disconnect the machine harness connector from the ECM.

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

4. Run the engine at high idle.

5. At the alternator, measure the voltage between contact 1 and contact 2.

Expected Result:

The voltage is greater than 24 DCV.

Results:

• YES - Voltage greater than 24 DCV is not the cause of the diagnostic code.

  Repair: Inspect the connector. Connect the machine harness to the ECM. Check all connectors in the wire harness. Make sure that the connections are clean and secure to the alternator and the ECM. If the diagnostic code remains active, replace the ECM. See Troubleshooting, "Electronic Control Module (ECM) - Replace" for more information.

  STOP

• NO - The voltage is less than 24 DCV. The alternator may have failed or the belt may be loose.

  Repair: Check the tension of the belt. If the tension of the belt is correct, the alternator has failed. Replace the alternator. Verify that the new alternator corrects the diagnostic code.

  STOP