Code
P1222
MINI
P — Powertrain
Accelerator pedal position (APP) sensor 2 - low input
Views:
UK: 2
EN: 2
RU: 4
AI status
Completed
Completed
100%
Causes
- Damaged or shorted wiring in the APP sensor 2 signal circuit (short to ground)
- Loose, corroded, or poorly connected sensor connector
- Failed APP sensor (internal short or open)
- Lost 5V reference or poor ground at the pedal sensor
- Mechanical binding or damage in the pedal assembly affecting the sensor
- ECU/PCM fault (rare) or intermittent faults in vehicle wiring harness
Symptoms
- Check engine / malfunction indicator lamp illuminated
- Reduced engine power or limp-home mode
- Delayed or no throttle response to pedal input
- Cruise control may be disabled
- Inconsistent or incorrect pedal position reading in scan tool data
What to check
- Read all stored codes and freeze frame data with a capable scan tool; note any related APP/throttle codes
- Check live data: monitor APP sensor 1 and sensor 2 voltages/percentages while operating pedal slowly
- Visually inspect pedal sensor connector and wiring for damage, corrosion, or loose pins
- With ignition ON (engine OFF), verify 5V reference and ground presence at the sensor connector
- Back-probe sensor signal and measure voltage at rest and while pressing the pedal
- Wiggle test wiring and connector while monitoring signal to find intermittent faults
Signal parameters
- Reference supply typically 5 V (verify against factory data)
- APP sensor 2 raw signal: normally a low-voltage at rest that rises with pedal travel (typical range ~0.5–4.5 V depending on design) — a 'low input' fault means the signal is below the expected lower threshold
- Sensor 1 and sensor 2 must correlate; significant mismatch or sensor 2 stuck at very low voltage indicates sensor/circuit issue
- Check for near-zero volts (short to ground) or open-circuit (no reference) conditions
Diagnostic algorithm
- Capture codes and freeze-frame; note related throttle/pedal codes (do not assume single-code cause).
- With ignition ON (engine OFF) use a scan tool to view live APP sensor 1 and sensor 2 readings while slowly operating the pedal. Observe behavior and correlation.
- Visually inspect pedal area, connector, and wiring harness for damage, corrosion, or loose terminals. Repair any obvious damage.
- Back-probe the sensor connector: verify 5V reference and ground are present and stable with ignition ON. Record measured voltages.
- Measure sensor 2 signal voltage at rest and while moving the pedal. If signal is very low or absent, check for short to ground on the signal wire.
- Perform continuity/resistance checks between the sensor connector and the ECU connector for the signal, reference, and ground circuits; repair any short/open.
- If wiring and connectors are good but signal remains low, replace the accelerator pedal sensor assembly per factory procedures.
- After repair, clear codes, perform key-on/self-test and a road test while monitoring live data to confirm proper operation and that code does not return.
- If code persists after sensor/wiring replacement, perform ECU input circuit tests or consult manufacturer guidance; consider ECU replacement only after exhausting wiring and sensor checks.
Likely causes
- Wiring/connector fault (open, short to ground, corrosion)
- Faulty accelerator pedal sensor assembly (sensor 2)
- Poor 5V reference or ground at the sensor
- Less likely: ECU input circuit failure
Fault status
Status
APP sensor 2 low input: ECU detected signal voltage below expected threshold from accelerator pedal position sensor 2.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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