P1121

Code

LEXUS P — Powertrain

Accelerator Pedal Position Sensor Range Performance Problem

Brand: LEXUS

Type: P — Powertrain

Views: UK: 27 EN: 80 RU: 37

AI status

Completed

ready

Completed 100%

Page language: EN

Faulty accelerator pedal position sensor (one or both sensor elements)
Damaged, corroded or loose connector(s) at the pedal assembly
Broken, shorted or high-resistance wiring between APPS and ECU (power, ground, signal)
Poor 5V reference or ground at the pedal sensor
Mechanical binding or obstruction of the accelerator pedal
Aftermarket cruise/throttle controller or incorrect replacement pedal

Scan for stored and pending codes and view freeze-frame and live data (APPS1, APPS2, throttle angle).
Visually inspect pedal assembly, wiring harness and connectors for damage, corrosion, or contamination.
Back-probe pedal sensor connector and measure reference voltage (typically 5 V), ground continuity, and each sensor output voltage with key ON engine OFF.
Observe live APPS1 and APPS2 values while slowly moving the pedal — signals should change smoothly and correlate according to the service manual.
Wiggle the harness and connector while monitoring signals to check for intermittent faults.
Compare actual voltages/behavior to vehicle-specific service manual specifications.

Reference (5 V) supply to APPS — present with key ON (check for stable ~5 V; consult service manual).
Ground continuity from pedal sensor ground pin to chassis/ECM ground.
APPS sensor outputs typically operate within ~0.2–4.8 V range; many Lexus/ Toyota pedals use complementary signals (one increases while the other decreases).
At rest (pedal released) typical values often near 0.5 V (sensor A) and ~4.5 V (sensor B) on complementary designs — verify against the model-specific service data.
Sensor outputs should change smoothly with pedal travel and maintain expected correlation (no sudden jumps or dropouts).

Retrieve all codes and freeze frame, note engine state when fault set.
Inspect pedal, harness and connectors for visible damage, corrosion, or water ingress. Repair obvious issues.
With key ON engine OFF, back-probe the pedal connector: verify 5 V reference, ground, and both sensor output voltages. Record idle/rest voltages.
Slowly depress and release pedal while monitoring APPS1 and APPS2 live data or voltmeter. Look for smooth, monotonic change and correct correlation between the two signals.
Perform a wiggle test on harness and connector while observing signals to find intermittent faults.
If reference or ground missing or out of range, trace and repair wiring to the ECM (check connector pins at ECM).
If wiring and power/ground are good but sensor outputs are out of range, replace the accelerator pedal assembly or sensor per service manual.
After repair, clear codes, perform any required throttle/pedal relearn or ECM adaptation procedure, then road test and confirm that code does not return.
If replacement pedal still shows incorrect signals or symptoms persist, consider ECM input testing or exchange as a last step (rare).

⚠️ Status

Accelerator Pedal Position Sensor Range/Performance problem detected — pedal sensor voltages out of expected range or sensor signals inconsistent.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0 - 2.5 hours

Your experience will help others

+100 karma for a short comment :)

Was this AI description helpful?

Your feedback helps improve AI descriptions.

👍 Like 0 👎 Dislike 0

Send to email

P1121 — Accelerator Pedal Position Sensor Range Performance Problem