CLIP (tab) 3P0572 - Caterpillar

Use this procedure to troubleshoot the electrical system if a problem is suspected with the power to the engines Electronic Control Module (ECM). Also, use this procedure if one of the following diagnostic codes is active or easily repeated.
Table 1
J1939 Code and Description Comments
158-2
Keyswitch Battery Potential : Erratic, Intermittent, or Incorrect The engine is running. The battery voltage falls below 18 VDC for one second. The voltage returns above 18 VDC.
Three voltage readings in the last 7 seconds were below 18 VDC.
The code is logged.
168-3
Battery Potential / Power Input #1 : Voltage Above Normal The battery supply voltage is greater than 32 VDC on 24 VDC systems for 0.5 seconds.
The ECM has been powered for 3 seconds.
The engine is running for at least 3 seconds.
The code is logged.
168-4
Battery Potential / Power Input #1 : Voltage Below Normal The 24 VDC voltage falls below 18 VDC for 0.5 seconds.
The 24 VDC voltage must return above 18.2 VDC for 3 seconds in order for the diagnostic to reset.
The engine is running for at least 3 seconds.
The code is logged.
Illustration 1 g03746407
For the complete circuit details, refer to the full schematic.
Table 2
Troubleshooting Test Steps Values Results
1. Check for Codes
A. Connect Cat® Electronic Technician (ET) to the service tool connector.
B. Determine if a code is active or logged.
Codes
Result: A -2, -3, or -4 code is active or logged.
Proceed to Test Step 2.
2. Inspect the Electrical Connectors and the Wiring
A. Turn the main disconnect switch to the OFF position.
B. Thoroughly inspect the connectors. Refer to Troubleshooting, "Electrical Connectors-Inspect" for additional information.
C. Perform a 45 N (10 lb) pull test on the connector wires.
D. Check the harness for abrasions and pinch points.
Connectors and Wiring
Result: The connectors and wiring appear to be OK.
Proceed to Test Step 3.
Result: There is a problem with the connectors and/or wiring.
Repair: Repair