PISTON AS 4T3272 - Caterpillar

System Operation Description:Use this procedure to troubleshoot the electrical system if a problem is suspected with a sensor supply or if any one of the diagnostic codes in Table 1 is active or easily repeated.
Table 1
Diagnostic Codes Table
Description Conditions which Generate this Code System Response
262-3 5 Volt Sensor DC Power Supply voltage above normal The analog sensor supply voltage is above normal for two seconds. The code is logged.
All sensors are set to default values.
262-4 5 Volt Sensor DC Power Supply voltage below normal The analog sensor supply voltage is below normal for two seconds.
263-3 Digital Sensor Power Supply (8V Or 12V) voltage above normal The digital sensor supply voltage is above normal for two seconds.
263-4 Digital Sensor Power Supply (8V Or 12V) voltage below normal The digital sensor supply voltage is below normal for two seconds. System OperationThe Electronic Control Module (ECM) supplies a regulated voltage of 5.0 0.2 VDC to the following sensors:
Aftercooler temperature sensor
Atmospheric pressure sensor
Coolant temperature sensor
Crankcase pressure sensor
Filtered engine oil pressure sensor
Filtered fuel pressure sensor
Turbocharger outlet pressure sensor
Left turbocharger inlet pressure sensor
Right turbocharger inlet pressure sensor
Unfiltered engine oil pressure sensor
Unfiltered fuel pressure sensorThe ECM supplies a regulated voltage of 8.0 0.4 VDC to the following sensors:
Left exhaust temperature sensor
Right exhaust temperature sensorThe supply voltage for the sensors is routed from the ECM to terminal A of each sensor connector. The sensor return for the sensors is routed from the ECM to terminal B of each sensor connector. The ECM provides short circuit protection for the internal power supply. A short circuit to the battery will not damage the internal power supply.Note: The sensors are not protected from overvoltage. A short from the supply line to the +Battery may damage the sensors. If the diagnostic code 262-3 or the diagnostic code 263-3 is logged, it is possible that all of the sensors have been damaged. Repair the sensor supply and check for any active sensor diagnostic codes in order to determine if a sensor has failed.
Illustration 1 g01240904
Typical schematic
Illustration 2 g01242535
P1 ECM connector
(P1-2) 5 V sensor supply (left rail)
(P1-3) Sensor return (left rail)
(P1-4) 8 V sensor supply
(P1-5) Digital return
(P1-18) 5 V sensor supply (right rail)
(P1-35) Sensor return (right rail)
Illustration 3 g01242538
P2 ECM connector
(P2-56) 8 V sensor supply
(P2-66) Digital return
Illustration 4 g01234146
Location of ECM connectors
Illustration 5 g01241329
Sensor connector
(Pin A) Sensor supply
(Pin B) Sensor return
(Pin C) Signal
Illustration 6 g01243506
Sensor connector
(Pin A) Sensor supply
(Pin B) Sensor return
(Pin C) Signal Test Step 1. Inspect Electrical Connectors and Wiring
Remove electrical power from the ECM.
Thoroughly inspect the J1/P1 ECM connector and the J2/P2 ECM connector. Inspect all of the connectors that are associated with the circuit. Refer to Troubleshooting, "Inspecting Electrical Connectors" for details.
Perform a 45 N (10 lb) pull test on each of the wires in the ECM connectors that are associated with the circuit.
Check the ECM connector (allen head screw) for the proper torque. Refer to Troubleshooting, "Inspecting Electrical Connectors" for details.
Check the harness and wiring for abrasion and for pinch points from the sensors back to the ECM. Expected Result:All connectors,