AccuGrade® Laser (CB420) Caterpillar

The AccuGrade - Grade Control System has lost communication with the laser receiver.

System Response:

Illustration 1	g00993805
(1) Laser receiver not connected (2) Laser receiver and electric mast not connected

The device icon for the laser receiver will be grayed out or missing from the display.

Test Step 1. INSPECT THE HARNESS.

Refer to Electrical Schematic.

1. Move the "Power/Setup" Switch on the display to the OFF position.

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

3. Disconnect the connectors of the harness for the right/left electric mast. Disconnect the harness connectors for the right/left laser receivers.

4. Carefully inspect each harness for signs of abrasion, nicks, or cuts.

   The following areas are locations that should be checked:

   • Exposed insulation

   • Points of rubbing wire

5. Check the connectors for moisture or corrosion.

   Note: If corrosion is evident on the contacts or the connector, use only denatured alcohol to remove the corrosion. Use a cotton swab or a soft brush to remove the corrosion. Do not use cleaners that contain trichloro-ethylene because trichloro-ethylene may damage the connector.

Expected Result:

The harnesses for the AccuGrade - Grade Control System should be free of corrosion, moisture and abrasion.

Results:

• OK - The harnesses for the AccuGrade - Grade Control System are free of corrosion, moisture, abrasion. Proceed to test step 2.

• NOT OK - A problem exists with the connector, the wiring or the wiring harness.

  Repair: Repair the affected harness for the AccuGrade - Grade Control System or replace the affected harness for the AccuGrade - Grade Control System.

  STOP

Test Step 2. CHECK IF THE DIAGNOSTIC CODE REMAINS

1. Reconnect the harnesses for the AccuGrade - Grade Control System to the left electric mast.

2. Reconnect the harnesses for the AccuGrade - Grade Control System to the left laser receiver.

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

4. Move the "Power/Setup" Switch on the display for the AccuGrade - Grade Control System to the ON position.

Expected Result:

The diagnostic code is no longer active.

Results:

• OK - The diagnostic code is no longer active.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

• NOT OK - The diagnostic code is still active. Proceed to Test Step 3.

Test Step 3. CHECK THE RESISTANCE OF THE CAN CIRCUIT

Illustration 2	g01379685

1. Place the key start switch and the disconnect switch in the OFF position.

2. Take the following measurement at the connector for the Right or Left Hand laser/sonic harness. Measure the resistance between contact C (wire L854-YL) and contact D (wire L855-GN).

Expected Result:

The resistance measurement is 60 ± 6 ohms.

Results:

• YES - The resistance measurement is 60 ± 6 ohms. Proceed to Test Step 4.

• NO - The resistance measurement is NOT 60 ± 6 ohms. Proceed to Test Step 4.

Test Step 4. CHECK THE CAN TERMINATION RESISTORS.

1. Place the key start switch and the disconnect switch in the OFF position.

2. Disconnect the 3-pin connector for all four of the termination resistors.

3. Measure the resistance between contact A (wire L854-YL) and contact B (wire L855-GN) for all four resistors. Note the resistance.

Expected Result:

The resistance measurement is 120 ± 12 ohms.

Results:

• YES - The resistance measurement is 120 ± 12 ohms. Reconnect the resistors.

  Repair: Contact your Technical communicator for a possible consultation with Caterpillar.

  STOP

• NO - One or all resistance measurements is NOT 120 ± 12 ohms.

  Repair: Replace the termination resistor(s) that did not measure 120 ± 12 ohms.

  STOP