GEAR-PLANETARY 3732980 - Caterpillar

System Operation Description:Use this procedure to troubleshoot the electrical system if a problem is suspected with the air/fuel pressure module 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    
94-3 Fuel Delivery Pressure Sensor : Voltage Above Normal     The duty cycle of the pressure sensor is outside the range of the sensor.
The frequency of the pressure sensor is outside the range of the sensor.     The code is logged.
The engine is shutdown.    
94-8 Fuel Delivery Pressure Sensor : Abnormal Frequency, Pulse Width, or Period    
106-3 Air Inlet Pressure Sensor : Voltage Above Normal    
106-8 Air Inlet Pressure Sensor : Abnormal Frequency, Pulse Width, or Period    Tubes that connect the air/fuel pressure module to the inlet air manifold and to the fuel manifold enable the module to sense the absolute inlet manifold air pressure and fuel pressure. The module calculates the differential pressure between the fuel manifold and the inlet air manifold. This fuel differential pressure is the value of the fuel pressure minus the value of the inlet manifold air pressure.Pulse Width Modulation (PWM) - This is a digital signal. The frequency is constant: the percent on time versus the period is called a duty cycle. If the signal is on for 50 percent of the period as an example, the duty cycle is 50 percent. This provides a more accurate status for a parameter than a signal that can only be ON or OFF.
Illustration 1 g01435459
Sample duty cycles that are low, medium, and high.The air/fuel pressure module sends PWM signals that represent the inlet manifold air pressure and the fuel differential pressure to the Electronic Control Module (ECM). The ECM uses the information to help calculate the fuel flow.The most likely causes of the diagnostic code are a poor connection or a problem in a wiring harness. The next likely cause is a problem with the module. The least likely cause is a problem with the ECM.Logged diagnostic codes provide a historical record. Before you begin this procedure, use Caterpillar Electronic Technician (ET) to print the logged codes to a file.The troubleshooting procedure may generate additional diagnostic codes. Keep your mind on correcting the cause of the original diagnostic code. Clear the diagnostic codes after the problem is resolved.
Illustration 2 g01439944
Schematic for the air/fuel pressure module on the in-line engines and the vee enginesThe air/fuel pressure module is connected to the ECM via the J6/P6 connectors on the terminal box.Test Step 1. Inspect the Electrical Connectors and Wiring
Illustration 3 g01431198
Terminal Box (1) ECM connector J2/P2 (2) ECM connector J1/P1 (3) 16 amp circuit breaker (4) Connectors J3/P3 for the customer's connector (5) Connectors J4/P4 for the optional control panel (if equipped) or for a customer's connector (6) J5/P5 connectors for the harness from the sensors (7) J6/P6 connectors for the harness from the sensors
Turn the engine control switch to the OFF/RESET