P2135

P2135 means the two redundant throttle/pedal position sensors aren't correlating with each other — TPS-A and TPS-B at the throttle body should track in opposite directions through the blade's full range, and APP-D and APP-E at the pedal should do the same. When either pair disagrees by more than the correlation window (usually about 8-10% of full scale for more than 100ms), P2135 sets and the ECM drops to limp mode immediately. This is the most common throttle code on GM full-size trucks and one of the most common across all platforms. The ECM doesn't tell you whether the fault is at the throttle body or the pedal — you have to determine that yourself. Cheapest-first: clear the code, then with the engine off and key on, scan-tool the live data and watch all four sensor values simultaneously while you slowly sweep the pedal from rest to full travel. APP-D and APP-E should mirror cleanly; TPS-A and TPS-B don't move yet (engine off). Then start the engine and watch the throttle sensors as the ECM commands blade movement — TPS-A and TPS-B should mirror cleanly. Whichever pair shows the dropout, flat-spot, or correlation break is the fault.

Vehicle-specific patterns: 2007-2014 GM full-size trucks and SUVs (Silverado / Sierra / Tahoe / Yukon / Suburban / Avalanche) with the 5.3L / 6.0L is the absolute textbook P2135 platform — APP-harness corrosion under the driver's-side carpet is so prevalent that GM issued multiple TSBs and many shops keep pedal-assembly pigtails in stock. The fix is repinning the connector or replacing the pedal-side pigtail; full pedal-assembly replacement runs $150-300. 2005-2010 Pontiac G6 / Saturn Aura with the 3.6L LY7 throws P2135 from internal TPS failure inside the throttle body — full throttle-body replacement required. 2008-2013 Toyota Sequoia / Tundra 5.7L 3UR-FE sees P2135 from carbon-buildup-induced TPS drift; throttle-body cleaning often resolves it. 2010-2014 Subaru Forester / Outback 2.5L throws P2135 from a known internal throttle-body TPS fault that was extended-warranty covered on certain VIN ranges. Critical: P2135 is the throttle code where the relearn matters most — after any pedal or throttle-body work on a GM truck, scan-tool the throttle-position-relearn procedure (GDS / Tech 2 / equivalent) or do the key-on / 30-second / key-cycle dance per the FSM; skip it and the correlation window will trip P2135 again within the first drive cycle even with brand-new parts installed.