The function diagram for the VREF includes the following:
• Engine Oil Pressure (EOP) sensor
• Exhaust Back Pressure (EBP) sensor
• Manifold Absolute Pressure (MAP) sensor
• Injection Control Pressure (ICP) sensor
• Brake Control Pressure (BCP) sensor (optional)
• Engine Fuel Pressure (EFP) sensor (optional)
• Water in Fuel (WIF) sensor (optional)
• Accelerator Position Sensor (APS)
• Barometric Absolute Pressure (BAP) sensor
• Electronic Control Module (ECM)
The ECM contains a regulated 5 V DC voltage reference source to power engine and vehicle sensors. The sensor signals are compared to the VREF to determine actual sensor output signal values.
These values are processed by the ECM for engine operation.
The system has two VREF circuits:
• VREF A for engine sensors
• VREF B for chassis sensors
NOTE: See truck Chassis Electrical Circuit Diagram Manual for APS and BAP sensor circuit diagrams.