Summary
P2135 means the two throttle position sensor (TPS) signals inside the electronic throttle body do not agree with each other, or the accelerator pedal position (APP) sensors are not correlating with the TPS. The most common causes are a failing throttle body with worn TPS elements (40%), a faulty accelerator pedal position sensor (25%), and wiring or connector issues (20%). The vehicle will enter reduced power mode (limp mode), severely limiting acceleration.
Severity: High — vehicle enters reduced power (limp) mode
Safe to drive: Yes, limited — limp mode restricts speed; diagnose promptly
Repair cost: $100–$600 depending on cause
DIY difficulty: Moderate
What does P2135 mean?
Modern vehicles use an electronic throttle control (ETC) system — also called "drive-by-wire" — where there is no physical cable between the gas pedal and the throttle body. Instead, the accelerator pedal position (APP) sensor sends a signal to the PCM, which then commands a motor in the throttle body to open the throttle plate.
For safety, the system uses redundant sensors. The throttle body contains two TPS sensors (TPS1 and TPS2) that report the throttle plate position independently. The accelerator pedal also has two APP sensors (APP1 and APP2). The PCM constantly compares these paired signals — they should track each other within a tight tolerance.
P2135 is set when the two TPS signals, or the TPS and APP signals, deviate from each other by more than the allowed tolerance. Because the PCM cannot determine which sensor is correct, it enters a failsafe reduced power mode — limiting throttle opening to approximately 5–15% to prevent unintended acceleration. This is a safety-critical system.