P1107

P1107 is the mirror twin of P1106 — GM's MAP Sensor Circuit Intermittent Low. The signal voltage briefly dropped below the expected floor (usually under 0.5V) and then recovered. Same 5V-reference MAP sensor as above: 1.0-1.5V key-on, 1.0-1.8V warm idle, 2.5-4.5V WOT or scaled higher on boosted applications. An intermittent-low fault almost always points at signal-wire issues, a bad ground, or a sensor that's losing internal continuity. Cheapest-first ladder: (1) Wiggle-test the MAP harness with the scan tool live-graphing voltage — broken signal wires drop the reading to near-zero when the harness flexes. (2) Check signal ground integrity — voltage-drop test from the sensor ground pin to battery negative with the key on, engine running; anything over 0.1V means a corroded ground point or broken ground wire. (3) Verify the 5V reference is present at the connector (should be 4.9-5.1V) — if the reference is missing, you're chasing back to the ECM connector or a shared reference circuit feeding multiple sensors. (4) Inspect the MAP vacuum port for engine-oil contamination from PCV blowby — oil pooled in the port can short the sensor element to ground intermittently. (5) Replace the sensor ($45-$90) only after wiring and ground are confirmed clean. Don't replace the MAP sensor before checking the shared 5V reference circuit — on LS trucks the MAP, TPS, and BARO can share a reference splice, and one chafed wire upstream will throw multiple intermittent-low codes that all clear after one repair.

Vehicle-specific patterns: 1999-2013 Silverado / Tahoe / Suburban / Sierra / Yukon with the LS Vortec V8s — the MAP harness routes across the back of the intake and chafes against the firewall or the EGR delete plate; vibration eventually breaks the signal-wire copper inside the insulation. 2005-2010 Cobalt / HHR / Ion with the 2.2/2.4 Ecotec frequently throws P1107 from a known ground-strap issue at the rear of the cylinder head — GM issued PI bulletins on the ground-strap routing. 2010+ Equinox / Terrain / Malibu with the 2.4L LAF/LEA Ecotec throws P1107 when the MAP connector wicks moisture from the cowl drain backing up — the pins corrode green inside a sealed-looking connector. 2010+ Camaro SS / CTS-V with the LSA/LS3 and 2014+ Corvette Stingray with the LT1 throw P1107 from supercharger-related MAP harness routing on the LSA and from intake-manifold flex on the LT1. Estimated repair: $0 (cleaning a corroded ground or reseating a connector) to $220 (MAP sensor + harness pigtail + ground-strap upgrade).