Automotive Service Excellence (ASE) A8 Engine PerformanceFuel, Air Induction, and Exhaust Systems Diagnosis and RepairMedium
A vehicle with an electronic throttle control (ETC) system experiences intermittent loss of throttle response and enters 'limp home' mode. The technician retrieves a P2135 (Throttle/Pedal Position Sensor/Switch 'A'/'B' Voltage Correlation) DTC. Which of the following is the MOST likely cause?
- AA faulty accelerator pedal position (APP) sensor.
- BA clogged air filter.
- CA low fuel pressure condition.
- DA restricted exhaust gas recirculation (EGR) valve.
Show answer & explanationAnswer & explanation
Correct answer: A. A faulty accelerator pedal position (APP) sensor.
The P2135 DTC specifically indicates a correlation issue between two different sensors (usually A and B) within the throttle position sensor or accelerator pedal position sensor. Since the symptom is loss of throttle response, and the code points to a correlation error, a faulty APP sensor (which directly controls throttle input) is the most probable cause.
Why the other options are wrong
- B. A clogged air filter would cause reduced power and potentially rich conditions, but not a P2135 DTC or sudden loss of throttle response.
- C. Low fuel pressure would cause lean conditions, misfires, or power loss, but not a P2135 DTC related to throttle position sensor correlation.
- D. A restricted EGR valve would primarily affect emissions and potentially cause drivability issues, but not a P2135 DTC or throttle response loss.
P2135 DTC (APP/TPS Correlation)
A diagnostic trouble code indicating a discrepancy in voltage readings between the redundant sensors within the accelerator pedal position (APP) sensor or throttle position sensor (TPS).
- Often related to electronic throttle control (ETC) systems.
- Triggers 'limp home' mode for safety.
- Requires replacement of the faulty sensor (APP or TPS) assembly.
Memory trick: P2135, check the pedal's alive!