P2135
Throttle/Pedal Position Sensor/Switch 'A' / 'B' Voltage Correlation
If your vehicle's onboard computer has flagged the diagnostic trouble code P2135, it refers to a detected anomaly regarding "Throttle/Pedal Position Sensor/Switch 'A' / 'B' Voltage Correlation". This systemic engine fault needs a targeted check before symptoms expand.
Driver's Summary
A P2135 fault code points directly to a problem with throttle/pedal position sensor/switch 'a' / 'b' voltage correlation that the ECM has confirmed over multiple drive cycles. The most common signs are limp mode, no throttle response, sudden stalling. Given the high severity of this code, continuing to drive risks significant mechanical damage. Have it diagnosed immediately.
Symptoms
Limp mode, no throttle response, sudden stalling
Common Causes
- Failed throttle body
- Faulty Accelerator Pedal Position (APP) sensor
- Corroded wiring
- PCM software issue
How to Fix
- 1 Replace electronic throttle body
- 2 Replace accelerator pedal assembly
- 3 Clean throttle body connector
- 4 Perform PCM update
Technical Explanation
P2135 is stored after the control module confirms the fault over multiple ignition cycles, ruling out transient electrical noise as the cause. The PCM distinguishes between electrical faults (circuit codes) and performance faults (rationality codes) by comparing the sensor's reported value against what other sensors would predict under the same engine operating conditions. Once confirmed, the code is stored as a permanent DTC and the MIL is activated. The freeze frame snapshot — recording RPM, load, coolant temperature, and fuel trim at fault detection — is also saved and is critical for accurate diagnosis.
Is It Safe to Drive?
This fault carries real mechanical risk. The root causes — including failed throttle body — can trigger a chain reaction of component failures if the vehicle continues to be driven. Have it towed or drive directly to a shop without delay.
Mechanic's Pro Tip
Module replacement should always be the last resort for P2135 after exhaustively verifying all power supply circuits, ground connections, and communication bus wiring. Use a wiring diagram to locate all fuses, relays, and ground points for the affected module, and measure voltage drop on each ground with the circuit loaded. A module "failure" is frequently a corroded ground eyelet or a weak battery causing brownout conditions — fix these first and you'll save hundreds of dollars on an unnecessary module replacement.
Throttle body: $300 - $600; Pedal assembly: $250 - $400