DRAC compensates for various axle and tire ratios by monitoring the Vehicle Speed Sensor (VSS) signal and modifying it before passing it on to the PCM and speedometer unit. On models equipped with a DRAC, VSS buffer is an internal part of DRAC.
Home/Chevrolet/Astro/Chevrolet Astro I (1985-2005)/Repair manual/Theory & Operation/Digital Ratio Adapter Controller (Drac)
Contents
Wiring diagrams Section: Theory & Operation- Introduction
- Terminology
- Intake Manifold Tuning Valve Assembly (Cpi)
- Speed Density
- Computerized Engine Controls
- Powertrain Control Module
- Arithmetic Logic Unit (Alu)
- Central Processing Unit (Cpu)
- Power Supply
- Memories
- Input Devices
- A/c on (A/c Request) Signal
- Battery Voltage
- Brake Switch Feedback
- Coolant Temperature Sensor (Cts)
- Cranking Signal
- Digital Ratio Adapter Controller (Drac)
- EGR Pintle Position
- Fuel Pump Feedback
- Gear Switches
- Knock Sensor (Ks)
- Manifold Absolute Pressure (MAP) Sensor
- Intake Air Temperature (IAT) Sensor (Some Engines)
- Oxygen Sensor (O2S)
- Park/neutral Position (Pnp) Switch
- Pressure Switch Manifold (Psm) (4L60-E & 4L80-E Transmission)
- RPM Reference Signal
- Throttle Position (Tp) Sensor
- Transmission Temperature Sensor (Tts) (4L60-E, 4L80-E
- Vehicle Speed Sensor (Vss)
- Output Signals
- ABS Control Motors ("S" & "T" Series with Vcm)
- A/c Clutch Relay
- Air Injection Control Solenoid
- Cruise Control Solenoids
- Service Engine Soon Light
- EGR Control Solenoid Valve
- Electronic Ignition (Ei)
- Esc Timing Retard
- Evrv Solenoid
- Fuel Injectors
- Fuel Module
- Fuel Pump & Fuel Pump Relay
- Hei-Est Ignition
- Idle Air Control (Iac) Valve
- Self-Diagnostics
- Serial Data
- Shift Solenoids (4L60-E, 4L80-E & 4T60-E Transmission)
- Torque Converter Clutch
- Transmission Shift Light (Manual Transmission)
- Fuel Pump
- Fuel Pressure Regulator (Cpi)
- Fuel Pressure Regulator (Tbi)
- Fuel Pump Relay
- Fuel Control
- Open Loop
- Closed Loop
- Central Port Injection (Cpi)
- Throttle Body Injection (Tbi)
- Fuel System Operating Modes
- Idle Speed
- Ignition System
- High Energy Ignition Electronic Spark Timing (Hei-Est) Distributor
- Ignition Timing Advance
- Esc Detonation Retard Operation
- Catalytic Converter
- Exhaust Gas Recirculation (EGR)
- Port EGR
- Linear EGR
- Negative Backpressure EGR
- Evaporative Emission Control
- Carbon Canister
- Canister Control Valve (Ccv) (Some Federal)
- Purge Control Solenoid
- Positive Crankcase Ventilation (PCV)
- Air Cleaner (Acl)
- Wax Pellet Controlled
- Self-Diagnostic System
- "Hard Failures"
- "Intermittent Failures"
- Service Engine/throttle Soon Light
- Miscellaneous PCM Controls
- A/c Clutch
- A/c Pressure Switches
- Cruise Control
- Electronic Transmission (4L60-E, 4L80-E & 4T60-E)
- Shift Light
- A/c Compressor
- Abbreviations
- Accessory Drive Belts
- Adjustments
- Airbag
- Anti-Lock/traction Control
- Application
- Automatic Trans
- Auxiliary Emission Control Systems
- Basic Trouble Shooting
- Brakes
- Charging System
- Check Lists
- Computer Relearn
- Cooling System (Mechanical)
- Cruise Control Systems
- Diagnostic Connector Locations
- Differentials & Drive Axles
- Door Locks & Anti-Theft Systems
- Driveline/axles
- Driveshaft & Universal Joints
- DTC Index
- Electrical
- Electrical Component Locations
- Emission Applications
- Engine
- Engine Performance
- Fuses & Circuit Breakers
- Gauges & Instrument Panels
- General Servicing - All Makes
- Heated Glass/defoggers
- Heater
- Identification
- Manual & Power Steering
- Manual HVAC System
- MAP Guidelines
- Mechanical
- Mechanical - Hydraulic
- Metric Conversions
- Mirrors
- Passive Restraints
- Pin Voltage Charts
- Procedures
- Removal & Installation
- Reset Procedures
- Restraints
- Rpo Codes
- Seats
- Sensor Range Charts
- Specifications
- Starter
- Steering
- Steering Column
- Steering Column Switches
- Suspension Front
- Suspension Rear
- Testing & Diagnostics
- Theory & Operation
- Traction Control Disable
- Transfer Case
- Transmission
- Wheel Alignment
- Windows
- Wiper/washer Systems
- Wiring Diagrams - Engine Performance