LINK AS-TRACK 4884082 - Caterpillar

MID 27 - Transmission/Chassis ECMCID 168 - Electrical System VoltageFMI 4 - Voltage Below NormalThis diagnostic code indicates that the "Transmission/Chassis ECM" detects the electrical system voltage is below normal.The following can cause this code:
Charging system component failure
Harness failure
ECM failureUse a calibrated digital multimeter for this procedure.Test Step 1. CHECK BATTERY VOLTAGE
Start and run the engine at high idle for several minutes.
Measure the voltage at the battery posts.Expected Result:The voltage is greater than 18 VDC.Results:
OK - The voltage is greater than 18 VDC. The battery voltage is correct. Proceed to Test Step 2.
NOT OK - The voltage is less than 18 VDC.Repair: Check the charging system.Use Troubleshooting, REHS0354 to check the components.STOPTest Step 2. CHECK THE SYSTEM VOLTAGE AT THE ECMThe engine remains running at high idle.Do not disconnect the harness from the ECM.
Use the digital multimeter to measure the voltage between all the possible sources of power and all possible sources of ground.Expected Result:The voltage is greater than 18 VDC.Results:
OK - The voltage is greater than 18 VDC. Proceed to Test Step 3.
NOT OK - The voltage is less than 18 VDCRepair: Repair or replace the harness.STOPTest Step 3. CHECK THE DIAGNOSTIC CODE
Inspect the harness.Clean the harness connector contacts.Inspect the harness connector contacts for corrosion or damage.Inspect the wire insulation for damage caused by heat, corrosion, or chafing.
Perform a 45 N (10 lb) pull test on each circuit wire.
Reconnect all harness connectors.Verify that the connectors are fully seated and the clips are fastened.
Check for intermittent problems. Use Cat® Electronic Technician (Cat® ET) and perform a wiggle test on the harness.
Turn on the disconnect switch and the key switch.
Operate the machine.
Determine if the diagnostic code is active.Expected Result:The diagnostic code is not active.Results:
OK - The diagnostic code is not active.Repair: The initial diagnostic code was probably caused by a poor connection at one of the connectors that was checked.Resume normal operation.STOP
NOT OK - The diagnostic code is active. The ECM may have failed.Repair: Exit this procedure and perform this procedure again. Contact the technical communicator at your Caterpillar dealer. If the ECM requires replacement, see Testing and Adjusting, "Electronic Control Module (ECM) - Replace".STOP