WHEEL 1V1687 - Caterpillar

System Operation Description:Use this procedure under the following conditions:This procedure tests whether the correct voltage is supplied by the wiring. Use this procedure if the diagnostic code is logged or active.
253-02 Personality Module erratic, intermittent, or incorrect Note: This code can be generated by rapidly cycling the keyswitch. If this occurs, clear the logged diagnostic codes in order to prevent future confusion or an incorrect diagnosis.The electronic service tool will indicate Low Battery Voltage if the ECM is not receiving the battery supply voltage.Also use this procedure if another procedure has directed you here.The following background information is related to this procedure:The ECM receives electrical power (battery voltage) through the wiring within the engine harness. The ECM input at connector P1:70 (keyswitch) receives battery voltage from the keyswitch when the keyswitch is in the ON position or the START position. The ECM will power up when the ECM detects battery voltage at the keyswitch. The ECM will power down when battery voltage is removed from the keyswitch.The cause of an intermittent power supply to the ECM can occur on either the positive side (battery +) or the negative side (battery -). Both sides are routed from the ECM to the battery. The connections for the battery + should be routed through a dedicated protection circuit.The engine ECM requires the keyswitch to be in the ON position in order to maintain communications.Temporarily bypassing the engine wiring may be an effective means of determining the root cause of intermittent problems such as intermittent shutdowns. If the symptoms disappear with the bypass wiring, the engine wiring is the cause of the fault. A means of bypassing engine wiring is explained in this test procedure.
Illustration 1 g01331516
Schematic of the power supply (31 pin MIC)
Illustration 2 g01331519
Schematic of the power supply (70 pin MIC)
Batteries give off flammable fumes which can explode.To avoid injury or death, do not strike a match, cause a spark, or smoke in the vicinity of a battery.
Test Step 1. Check The Batteries
Measure no-load battery voltage at the battery posts.
Load test the batteries.Note: The batteries must pass the load test. The minimum voltage must be 11.5 Volts DC for a 12 Volt battery. If the battery voltage of a 12 Volt battery is below 12.4 Volts DC, the battery must be charged.Expected Result:The batteries provide sufficient voltage.Results:
OK - Proceed to Test Step 2.
Not OK - Recharge or replace the batteries. Verify that the repair eliminates the fault.STOPTest Step 2. Inspect Electrical Connectors And WiringNote: If the system has a 31 pin MIC, pins P1:57 and P1:69 are not used.
Illustration 3 g01625208
ECM pin locations
(56) Battery +
(57) Battery +
(68) Battery -
(69) Battery -
(70) Keyswitch
Thoroughly inspect the harness connector J1/P1. Also inspect the connections for the battery and the connections to the keyswitch. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the following connections:
P1:56 and P1:57 (Battery +)
P1:68 and P1:69 (Battery -)
P1:70 (Keyswitch)
Check the ECM