P2135 indicates the engine computer has detected a mismatch between the redundant throttle pedal position sensor circuits (A and B). These circuits are designed to track together, and a voltage correlation error means their signals have diverged beyond an acceptable range, triggering a safety fallback.
Internal sensor degradation causes the two redundant signal tracks to drift apart, triggering the correlation fault.
Chafed, corroded, or loose wiring and terminals in the pedal sensor circuit can alter voltage on one channel, breaking correlation.
On drive-by-wire systems, internal faults in the throttle body position sensors can also set this code if the PCM cross-references pedal and throttle data.
A poor ground or unstable 5V reference supply shared between the sensor circuits can skew one signal relative to the other.
Extremely rare; the engine computer is almost never the cause and should only be suspected after every other possibility is eliminated.
The definition is universal; the diagnostics are engine-specific. Open your vehicle for the codes documented for it:
It is risky. The vehicle will likely enter reduced-power or limp-home mode, and throttle response may be unpredictable. Have it diagnosed before extended driving.
Almost never. Shops or forums sometimes jump to PCM replacement, but the overwhelming real-world cause is a failed pedal position sensor, throttle body, or wiring issue. The computer is the last suspect, not the first.
Drive-by-wire systems use two separate sensor channels that output proportional voltages. The PCM compares them; if they disagree beyond a small tolerance, the correlation check fails and sets P2135.
No. The accelerator pedal position sensor (APP) reads driver pedal demand, while the throttle position sensor (TPS) reads the actual throttle blade angle. Both are part of the electronic throttle system, and P2135 most commonly points to the APP side.