HEAD 1262047 - Caterpillar

System Operation Description:Use this procedure to troubleshoot any suspect problems with the following sensors:
Fuel pressure sensor
Engine oil pressure sensor
Turbocharger outlet pressure sensor
Atmospheric pressure sensor
Auxiliary pressure sensorThis procedure covers the following open circuit diagnostic codes and short circuit diagnostic codes:
94-03
94-04
100-03
100-04
273-03
273-04
274-03
274-04
1835-03
1835-04The troubleshooting procedures for the diagnostic codes of each pressure sensor are identical. The Electronic Control Module (ECM) supplies 5 0.2 VDC to terminal A of each sensor. The sensor common connection is connected to terminal B of each sensor. The signal voltage from terminal C of each sensor is sent to the appropriate terminal on the ECM.Pull-up VoltageThe ECM continuously outputs a pull-up voltage on the circuit for the sensor signal wire. The ECM uses this pull-up voltage in order to detect an open in the signal circuit. When the ECM detects the presence of a voltage that is above a threshold on the signal circuit, the ECM will generate an open circuit diagnostic code (-03) for the sensor.The presence of pull-up voltage at the sensor connector indicates that the wires from the sensor connector to the ECM are not open. The absence of pull-up voltage at the sensor connector indicates an open in the signal wire. If the voltage at the sensor connector is different from pull-up voltage, the signal wire is shorted to another wire in the harness.
Illustration 1 g01145390
Schematic for C-10 engines
Illustration 2 g01148768
Schematic for C-15 engines
The connection of any electrical equipment and the disconnection of any electrical equipment may cause an explosion hazard which may result in injury or death. Do not connect any electrical equipment or disconnect any electrical equipment in an explosive atmosphere.
Test Step 1. Inspect the Electrical Connectors and the Wiring
Turn the keyswitch to the OFF position.
Thoroughly inspect all connectors that are associated with the +5 V sensor supply for your engine. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
Illustration 3 g01145553
C-10 engine (left side engine view) (1) Fuel pressure sensor (2) Atmospheric pressure sensor (3) Turbocharger outlet pressure sensor (4) P61 customer connector (5) Engine oil pressure sensor (6) ECM (7) P2/J2 ECM connector (8) P1/J1 ECM connector
For C-10 engines, inspect connectors (4), (7), and (8). Also inspect each of the connectors for sensors (1), (2), (3), and (5) .
Illustration 4 g01145557
C-15 engine (left side engine view) (9) P61 customer connector (10) Turbocharger outlet pressure sensor (11) Fuel pressure sensor (12) Atmospheric pressure sensor (13) Engine oil pressure sensor (14) ECM (15) P2/J2 ECM connector (16) P1/J1 ECM connector
For C-15 engines, inspect connectors (9), (15), and (16). Also inspect each of the connectors for sensors (10), (11), (12), and (13) .
Illustration 5 g01145450
P2 ECM connector for C-10 and C-15 engines (P2-2) +5 V Sensor supply (P2-3) Sensor return (P2-14) Atmospheric pressure sensor (P2-16) Fuel pressure sensor (P2-24) Engine oil pressure sensor (P2-40) Turbocharger outlet pressure sensor
Illustration 6 g01145447
P1 ECM connector for C-10 and C-15 engines (P1-2) +5 V Sensor supply (P1-3) Sensor return (P1-15) Auxiliary pressure sensor
Illustration 7 g01145543
P61 Customer connector (P61-2) +5 V Sensor supply (P61-3) Sensor return (P61-15) Auxiliary pressure sensor
Illustration 8 g01123211
Connectors for the