Code
P1222
FIAT
P — Powertrain
Accelerator potentiometer track 2 fault | Drive-by-wire potentiometer 2 signal implausible
Views:
UK: 2
EN: 5
RU: 5
AI status
Completed
Completed
100%
Causes
- Faulty accelerator pedal position sensor (potentiometer) — track 2
- Damaged, corroded, or disconnected connector at the pedal sensor
- Broken, shorted, or open wiring between pedal sensor and ECU
- Poor ground or 5V reference supply fault to the pedal sensor
- Intermittent contact from moisture/contamination or mechanical wear inside pedal
- ECU input circuit fault (less common)
Symptoms
- Reduced engine power / limp-home mode
- Loss of accelerator response or delayed/throttled acceleration
- Check Engine Light (MIL) illuminated with P1222 stored
- Erratic or jumping throttle behavior in drive-by-wire systems
- Pedal position readings out of expected range or mismatch in live data
What to check
- Read and record freeze-frame and live PID data for both pedal tracks with a scan tool
- Visually inspect pedal connector, wiring harness, and ECU connector for damage or corrosion
- Check for other stored codes that may indicate supply or CAN/ECU issues
- Measure reference 5V supply and ground at the pedal connector with ignition ON, engine OFF
- Backprobe and measure both pedal signal voltages while slowly moving the pedal through full travel
- Perform wiggle test on wiring while monitoring live data to find intermittent faults
Signal parameters
- Reference supply: nominal 5 V (measured at pedal connector with key ON)
- Ground: solid chassis/ECU ground (low ohm to battery negative)
- Signal output (both tracks): varies smoothly with pedal travel — typically ~0.2–4.8 V across travel (model dependent)
- Tracks should be linear and correlate with each other; no sudden jumps or dropouts
- No short to battery (near 12 V) or to ground (0 V) on the signal lines under normal conditions
Diagnostic algorithm
- Use a compatible scanner to read code P1222 and check related codes and live data (pedal track 1 & 2 PIDs).
- Verify symptom reproduction and record signal behavior while slowly operating the pedal — look for jumps, flat spots, or nonlinearity.
- Visually inspect pedal connector and harness; repair any damaged insulation, pins, or corrosion.
- With ignition ON (engine OFF), backprobe the pedal connector: verify 5V reference present, good ground, and that track 2 signal changes with pedal movement.
- If reference or ground is missing or unstable, trace and repair supply wiring or ECM power/ground issues.
- If supply is good but track 2 signal is out-of-range, test continuity between pedal signal pin and ECU pin; check for short to battery/ground.
- If wiring and ECU connections test good, replace the accelerator pedal assembly (both tracks) with a known-good unit and clear codes.
- After replacement, perform any required throttle/pedal relearn or calibration per manufacturer procedure and road test to confirm repair.
- If fault persists with new pedal and wiring verified, consider ECU input fault — refer to manufacturer guidance and ECU testing.
Likely causes
- Wiring harness chafe or pinched conductor between pedal and ECU
- Connector corrosion or bent terminal at pedal or ECU
- Internal failure of the pedal assembly (track 2 element failure)
- Short to battery or ground on the track 2 signal wire
- Failed 5V reference or ground on pedal sensor (supply-side issue)
Fault status
Status
Accelerator potentiometer track 2 signal implausible — check pedal sensor, wiring, and 5V/ground supply.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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