Walker Products 225-91001 Manifold Absolute Pressure Sensor Measures manifold pressures through changing voltage and sends this information to the onboard computer The computer uses the information received and other inputs to calculate the correct amount of fuel delivered Symptoms of failure include poor starting, detonation, a check engine light, and or no start conditions Sensors are non-serviceable and therefore must be replaced when non-functional Manufactured to meet or exceed OEM standards and specifications