HOSE AS 8E1290 - 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    
41-3 8 Volt DC Supply : Voltage Above Normal     The digital sensor supply voltage is above normal.     The code is logged.
All sensors are set to default values.    
41-4 8 Volt DC Supply : Voltage Below Normal     The digital sensor supply voltage is below normal.    
232-3 5 Volt Sensor DC Power Supply : Voltage Above Normal     The sensor supply voltage is above normal.     The code is logged.
All sensors are set to default values.    
232-4 5 Volt Sensor DC Power Supply : Voltage Below Normal     The sensor supply voltage is below normal.    
262-3 5 Volt Sensor DC Power Supply : Voltage Above Normal     The sensor supply voltage is above normal.     The code is logged.
All sensors are set to default values.    
262-4 5 Volt Sensor DC Power Supply : Voltage Below Normal     The sensor supply voltage is below normal.    
263-3 Digital Sensor Power Supply (8V Or 12V) : Voltage Above Normal     The digital sensor supply voltage is above normal.     The code is logged.
All sensors are set to default values.    
263-4 Digital Sensor Power Supply (8V Or 12V) : Voltage Below Normal     The digital sensor supply voltage is below normal.    System OperationThe Electronic Control Module (ECM) supplies a regulated voltage of 5.0 0.2 VDC to the following sensors:
Engine oil pressure
Atmospheric pressure
Fuel pressure
Turbocharger outlet pressure sensor
Engine coolant temperature
Inlet air temperature
Fuel temperature
Auxiliary pressureThe ECM supplies a regulated voltage of 8.0 0.4 VDC to the following sensors:
Coolant level sensor
Auxiliary 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 any of the -3 diagnostic codes are active, it is possible that a sensor has 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 g01429695
Typical schematicTest Step 1. Inspect Electrical Connectors and Wiring
Remove electrical power from the ECM.
Illustration 2 g01430140
ECM (1) J1/P1 connectors (2) J2/P2 connectors
Thoroughly inspect the J1/P1 and the J2/P2 ECM connector. Inspect all of the connectors that are associated with the circuit.Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
Illustration 3 g01430145
P1 ECM connector (P1-2) Coolant level (P1-29) Digital return (P1-30) Sensor return (P1-35) + 8 V digital supply (P1-36) + 5 V