Code
P1223
MINI
P — Powertrain
Accelerator pedal position (APP) sensor 2 - high input
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UK: 1
EN: 0
RU: 1
AI status
Completed
Completed
100%
Causes
- Short to battery voltage on APP sensor 2 signal circuit
- Open or damaged wiring harness or connector (corrosion, pin damage)
- Failed accelerator pedal module (internal sensor 2)
- Poor ground or missing reference/5V supply to pedal module
- Intermittent or corroded connector/contact
- Faulty engine control module (rare)
Symptoms
- Malfunction Indicator Lamp (MIL) / Check Engine Light on
- Reduced engine power / limp-home mode or throttle limp
- Poor or no throttle response from accelerator pedal
- Stored P1223 code (may be accompanied by other APP/Throttle codes)
- Intermittent throttle behavior if wiring fault is intermittent
What to check
- Read stored freeze-frame and pending codes with a capable scan tool; note any related APP or throttle codes
- Visually inspect the accelerator pedal assembly, connector and wiring harness for damage, corrosion, or pin push-out
- Backprobe APP sensor 2 signal, reference (5V) and ground at pedal connector with ignition ON (engine OFF) and observe voltages
- Compare APP sensor 1 and sensor 2 live data for correlation and plausibility while slowly depressing the pedal
- Perform wiggle test on harness while monitoring live data to reproduce fault
- Measure voltage at the ECU pin for APP sensor 2 with connector disconnected to check for short to B+ at ECU side
Signal parameters
- Reference supply (typical): ~5.0 V (key ON) to pedal sensor module
- Signal expected range (typical): ~0.5–4.5 V depending on pedal position; should change smoothly with pedal movement
- High-input fault: signal stuck near battery voltage or above expected upper threshold (eg >4.9–5.0 V) or sudden spikes above expected range
- Correlation: sensor 1 and sensor 2 should track together (either similar slope or defined relation); significant contradiction triggers correlation faults
Diagnostic algorithm
- Verify the code and capture live data and freeze-frame info with scan tool. Note any other related DTCs (APP, throttle actuator).
- Visually inspect pedal assembly, harness and connectors for obvious damage, water ingress, pins pushed out, or corrosion. Repair any visible damage.
- With ignition ON (engine OFF), backprobe pedal connector: confirm 5V reference and ground are present and stable. If reference missing or unstable, trace to ECU/PCM.
- Measure APP sensor 2 signal voltage at rest and while slowly pressing pedal. If voltage is >4.9 V or equal to battery voltage, suspect short to B+ or internal sensor fault.
- Compare sensor 1 and sensor 2 live voltages. If sensor 1 is plausible and sensor 2 is high, focus on sensor 2 circuit (wiring to pedal or pedal module). If both are abnormal, suspect reference or ECU.
- Disconnect pedal connector and measure voltage at the ECU pin for sensor 2. If the ECU pin reads battery voltage with the sensor disconnected, suspect ECU or short in harness to B+. If ECU pin reads normal reference (or open), suspect pedal assembly.
- Perform continuity/resistance checks of signal wire between pedal connector and ECU with battery negative disconnected. Check for short to B+ and short to ground.
- If wiring and connector check good but sensor 2 still high, replace the accelerator pedal module. Reconnect, clear codes and retest.
- If fault remains after pedal replacement and wiring checks, consider ECU diagnostic/replacement as last step; consult manufacturer procedures before replacing ECU.
- After repair, clear codes and verify proper operation under load and that DTC does not return.
Likely causes
- Short to +12V on APP sensor 2 signal or reference circuit
- Internal failure of pedal assembly sensor 2
- Connector terminal corrosion or bent pin at pedal or ECU
- Broken insulation causing chafe to a power wire
- Loss of proper ground or 5V reference to pedal module
Fault status
Status
APP sensor 2 circuit high input detected. The ECM/PCM has seen a voltage above the expected range on the accelerator pedal position sensor 2 circuit. Possible causes include a short to battery, wiring/connector fault, or failed pedal sensor. Throttle may be limited (limp mode). Recommend inspecting wiring, measuring reference and signal voltages, and replacing the pedal module only after confirming wiring/ECU conditions.
Repair difficulty: Medium
Diagnostic time: 1.0-2.0 hours
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