Code
P1222
ALFA ROMEO
P — Powertrain
Accelerator potentiometer track 2 fault | Drive-by-wire potentiometer 2 signal implausible
Views:
UK: 3
EN: 5
RU: 5
AI status
Completed
Completed
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Causes
- Open or short in accelerator pedal sensor (track 2) wiring
- Corroded, loose or damaged pedal connector or terminals
- Failed accelerator pedal position sensor (track 2) inside the pedal assembly
- Poor ground or 5V reference supply from the ECU
- Intermittent wiring harness damage (chafing, water intrusion)
- Software/ECU fault (rare)
Symptoms
- Check engine/warning light illuminated
- Reduced engine power / limp-home mode / limited throttle response
- Engine may not respond to accelerator pedal input or response is delayed
- Possible inconsistent throttle behavior or sudden surges when pressing pedal
What to check
- Retrieve freeze frame and live data with a capable scan tool (read both pedal tracks and throttle demand)
- Visually inspect accelerator pedal connector and wiring harness for damage, corrosion, or water entry
- Wiggle test: monitor track 2 signal while moving harness and pedal connector to look for intermittent changes
- Check for other related DTCs (throttle body, reference voltage, CAN bus)
- Measure reference voltage (typically ~5V) and ground at the pedal connector with key ON, engine OFF
Signal parameters
- Typical APP potentiometer signals: 0.5–4.5 V sweep across full pedal travel (varies by model)
- Track 1 and track 2 should move together and show a consistent linear relationship; difference beyond expected tolerance (manufacturer-specific) is implausible
- Open circuit: signal near 0 V; short to battery: signal near battery voltage (≈12 V) — both are fault indications
Diagnostic algorithm
- Read and record DTC(s) and live data for both pedal tracks and throttle position with a diagnostic scan tool.
- Perform visual inspection of pedal connector and wiring for corrosion, bent pins, damage or water contamination.
- With key ON (engine OFF) measure reference voltage and ground at the pedal connector; confirm ~5V reference and good ground continuity to chassis/ECU.
- Monitor live voltages/signals for track 1 and track 2 while slowly operating the pedal; note ranges, linearity, and any dropouts or noise.
- If reference and ground are correct but track 2 is out of range or inconsistent, backprobe connector and wiggle harness to locate intermittent wiring faults.
- Check continuity between pedal connector and ECU connector for track 2, reference 5V and ground; repair any opens/shorts.
- If wiring and connectors test good, replace or bench-test the accelerator pedal assembly (compare track 1 vs track 2 behavior).
- After repair, clear codes and perform accelerator pedal calibration/relearn if required by manufacturer; re-check for return of code and verify normal throttle response.
- If faults persist after replacing pedal and repairing wiring, inspect ECU power/ground and consider ECU diagnosis or replacement as last resort.
Likely causes
- Dirty/corroded connector at pedal assembly or ECU
- Broken wire or high-resistance splice to sensor track 2
- Internal failure of pedal potentiometer (track 2)
- Loss of reference 5V or ground affecting sensor readings
Fault status
Status
Accelerator potentiometer track 2 fault — drive-by-wire potentiometer 2 signal implausible. Check pedal sensor, wiring, reference supply and grounding.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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