To share the excessive load on the service brakes and for safety of the engine valve trains in downhill gradients heavy duty diesel engines are installed with exhaust brake.The duty cycle of an engine is high in mid-range speeds, thus an exhaust brake system with higher braking power at mid- range speeds is required. Automatic actuation of exhaust brake will ensure effective utilization of the available engine braking power and safety. A higher braking efficiency will also lead to improved vehicle downhill performance. This calls for design and application of constant pressure exhaust brake controlled through Electronic Control Unit (ECU) of the vehicle.In the present work, an attempt to applicate constant pressure exhaust brake controlled through ECU of the vehicle on 5.7 l heavy duty diesel engine was made. The limitations of the system were reviewed. A 1-D thermodynamic simulation was used to predict the performance of exhaust brake. This thermodynamic simulation allows iterative investigation for all design changes with negligible costs on physical prototyping and testing. The simulation results were compared with the experimental results to validate the model and check its accuracy. The performance was further compared with conventional fixed orifice exhaust brake system. Further, a control system with a logic diagram to effectively utilize the engine braking power was developed and validated on vehicle. Finally, vehicle downhill performance was evaluated with application of constant pressure exhaust brake and a comparison with fixed orifice exhaust brake system was made.