Order GMC Envoy MAP Sensor online today. Free Same Day Store Pickup. Check out free battery charging and engine diagnostic testing while you are in store.. It indicates your GMC Envoy’s MAP manifold absolute pressure sensor’s voltage reading is outside of the normal operating range. The voltage is too high. It’s most commonly caused by a bad MAP sensor, wiring issue, or vacuum leak. The MAP sensor measures the air pressure coming into your Envoy.