Walker Products Manifold absolute pressure sensors (MAP Sensor) measure manifold pressures through changing voltage and sends this information to the onboard computer. The computer uses this 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. Walker Products began supplying the fuel system and engine management needs of the automotive industry since 1946. We continue our commitment to supplying products manufactured to meet or exceed OEM standards and specifications with the highest quality products. 1997-2002 Nissan Altima,Isuzu Frontier,Chevrolet G20,Hyundai I30,Nissan Maxima,Nissan Pathfinder,Infiniti Q45,Nissan Quest,Mercury Villager,Nissan Xterra,