ATTACHMENT 8B7551 - Caterpillar

Illustration 1 g02758942
Schematic of the 583T, 587T, PL83, and PL87 Display Power Supply
Illustration 2 g02759037
Schematic of the 572R Series II Display Power SupplyThis diagnostic code is recorded when the ECM reads the voltage of the display power supply circuit and the voltage is above normal. Normal display power supply voltage is 9.0 0.5 VDC. The schematic that is shown above represents a typical installation of the component. Verify the connector contact and wire numbers by using the Electrical System Schematic for the machine that is being serviced.Test Step 1. CHECK THE VOLTAGE AT THE ECM.
Use the 7X-1710 Multimeter Probe Group. Check the voltage at the connector for the ECM. Measure the voltage from the contact 2 to the contact 2 (ground).
DO NOT disconnect the harness from the ECM.
The correct voltage should measure 9.0 0.5 VDC.Expected Result:The voltage that is measured is 9.0 0.5 VDC.Results:
OK - The voltage is 9.0 0.5 VDC. The display power supply voltage is correct. Check the ECM for the same diagnostic code. If the service code indicator is still ON, the ECM has failed.Repair: An ECM failure is unlikely. Exit this procedure and perform this procedure again. Also, recheck if the diagnostic code indicator is illuminated for this diagnostic code. If the cause of the diagnostic code is not found, replace the ECM. See Troubleshooting, "Main Display Module - Replace".STOP
NOT OK - The voltage is NOT 9.0 0.5 VDC. The display power supply voltage is NOT correct. Proceed to test step 2.Test Step 2. CHECK FOR A SHORT TO +BATTERY
Disconnect the machine harness from the ECM.
At the machine harness connector for the ECM, measure the voltage from the connector contact 34 to 2 (ground).Expected Result:The voltage that is measured is 0.0 0.5 VDC.Results:
OK - The voltage is 0.0 0.5 VDC. The voltage is correct. The ECM has failed.Repair: An ECM failure is unlikely. Exit this procedure and perform this procedure again. Also, recheck if the diagnostic code indicator is illuminated for this diagnostic code. If the cause of the diagnostic code is not found, replace the ECM. See Troubleshooting, "Main Display Module - Replace".STOP
NOT OK - The voltage is NOT 0.0 0.5 VDC. The harness has failed.Repair: Repair the harness or replace the harness.STOP