CD54 Paving Compactor Caterpillar

Illustration 1	g01946173
Schematic for the Water Spray Timer Potentiometer

Illustration 2	g01947038
Water Spray Timer Potentiometer

The Flash Code 4-2 is associated with the Water Spray Timer Potentiometer. The 4-2 flash code means that the Side Console ECM has lost the connection to the Potentiometer. This is a Level 1 fault. The 4-2 flash code indicates a Level 1 fault. The ECM has determined that the signal is out of range.

Note: Before performing this procedure, inspect the harness connectors that are involved in the circuit. Poor connections can often be the cause of a problem in an electrical circuit. Verify that all connections in the circuit are clean, secure and in good condition. If a problem with a connection is found, correct the problem and verify that this flash code is active before performing this procedure.

Possible conditions which could occur in this circuit include the following:

• Open circuit

• Short to Battery

• Short to Ground

• Faulty potentiometer

Test Step 1. CHECK THE CONTINUITY OF THE CIRCUIT

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

2. Disconnect the potentiometer from the machine harness.

3. Place a jumper from pin A (Wire 199-OR) to pin C (Wire N929-YL) of the connector for the potentiometer.

4. Disconnect the harness connector at the ECM.

5. Connect the red lead from a multimeter to pin 8 (Wire J844-GY) of the harness connector for the ECM.

6. Connect the black lead from the multimeter to pin 28 (Wire N929-YL) of the harness connector for the ECM.

7. Place the multimeter in the "Diode Check" mode.

8. Measure the voltage drop from pin 8 (Wire J844-GY) to pin 28 (Wire N929-YL) of the harness connector for the ECM.

9. Reverse the leads of the multimeter. Place the red lead on pin 28 (Wire N929-YL). Place the black lead on pin 8 (Wire J844-GY).

10. Measure the voltage drop from pin 28 (Wire N929-YL) to pin 8 (Wire J844-GY) of the harness connector for the ECM.

Expected Result:

The voltage drop from pin 8 (Wire J844-GY) to pin 28 (Wire N929-YL) is 0.4 ±0.2 VDC. The voltage reading from pin 28 (Wire N929-YL) to pin 8 (Wire J844-GY) shows overload (OL).

Results:

• OK - The first voltage reading is 0.4 ±0.2 VDC. The second voltage reading is overload (OL). The circuit and the diode are OK. Proceed to Test Step 2.

• NOT OK - The voltage readings are both 0 volts.

  Repair: There is a short in the circuit. Repair the harness or replace the harness or replace the diode pack.

  STOP

• NOT OK - The voltage readings are both overload (OL).

  Repair: There is an open in the circuit. Repair the harness or replace the harness or replace the diode pack.

  STOP

Test Step 2. CHECK THE POTENTIOMETER

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

2. The machine harness remains disconnected from the potentiometer.

3. Measure the resistance from contact A (wire A916-GN) to contact C (wire N929-YL) of the harness connector for the potentiometer.

4. Manipulate the potentiometer from the minimum limit to the maximum limit of rotation. Measure the resistance at the minimum limit and the maximum limit.

Expected Result:

The resistance varies from 0 to 1000 ±200 ohms.

Results:

• YES - The resistance varies from 0 to 1000 ±200 ohms. Proceed to Test Step 3.

• NO - The resistance does NOT vary from 0 to 1000 ±200 ohms. The potentiometer has failed.

  Repair: Replace the potentiometer.

  STOP

Test Step 3. CHECK THE CALIBRATION OF THE POTENTIOMETER

1. Refer to Systems Operation Testing and Adjusting, KENR5740, "Potentiometer (Water Timer) - Calibrate".

Results:

• OK - The potentiometer is now calibrated. Proceed to Test Step 4.

Test Step 4. CHECK IF THE FLASH CODE REMAINS

Note: A shorted circuit may have also blown the fuse. Repair the short before replacing the fuse.

1. Inspect the contacts and clean the contacts of the harness connectors.

2. Reconnect all harness connectors.

3. Operate the machine.

4. Check if the Flash Code remains.

Expected Result:

The Flash Code remains active.

Results:

• YES - The Flash Code remains active. 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, contact the Technical Communicator for your dealership for possible consultation with Caterpillar. This consultation may greatly reduce repair time. If the ECM requires replacement, see Testing and Adjusting, "Electronic Control Module (ECM) - Replace".

  STOP

• NO - The Flash Code is no longer active. The initial flash code was probably caused by a poor electrical connection or a short at one of the harness connectors that was disconnected and reconnected. Resume normal machine operation.STOP