CLAMP AS-COMPRESSOR 1895124 - 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
Code and 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 0.5 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
Left turbocharger inlet pressure sensor
Right turbocharger inlet pressure sensor
Turbocharger outlet 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 sensor
Coolant level sensor
Coolant level sensor for the separate circuit aftercooler (SCAC)The 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 g01441618
Typical schematic of the analog sensor supply
Illustration 2 g01440728
Typical schematic of the digital sensor supply
Illustration 3 g01441610
P1 ECM connector
(P1-2) Analog sensor supply
(P1-3) Analog sensor return
(P1-4) Digital sensor supply
(P1-5) Digital sensor return
(P1-6) Coolant level sensor for the separate circuit aftercooler (SCAC)
(P1-7) Coolant temperature sensor
(P1-11) Left exhaust temperature sensor
(P1-12) Right exhaust temperature sensor
(P1-15) Coolant level sensor for the separate circuit aftercooler (SCAC)
(P1-16) Filtered engine oil pressure sensor
(P1-17) Unfiltered engine oil pressure sensor
(P1-18) Analog sensor supply
(P1-24) Filtered fuel pressure sensor
(P1-25) Unfiltered fuel pressure sensor
(P1-30) Coolant level sensor
(P1-35) Analog sensor return
Illustration 4 g01441616
P2 ECM connector
(P2-36) Turbocharger outlet pressure sensor
(P2-37) Atmospheric pressure sensor
(P2-38) Left turbocharger inlet pressure sensor
(P2-39) Right turbocharger inlet pressure sensor
(P2-46) Crankcase pressure sensor
(P2-54) Digital sensor return
(P2-56) Digital sensor supply
(P2-57) Digital sensor supply
(P2-65) Digital sensor supply
(P2-66) Digital sensor return
Illustration 5 g01094844
Sensor connector
(Pin A) Sensor supply
(Pin B) Sensor return
(Pin C) Signal
Illustration 6 g01234146
Location of ECM connectors
Test Step 1. Inspect Electrical Connectors and Wiring
Turn the main disconnect switch to the OFF position.
Thoroughly inspect the