Code
P1122
FIAT
P — Powertrain
Throttle position sensor [signal implausible] | Throttle potentiometer track 2
AI status
Completed
Completed
100%
Causes
- Faulty throttle position sensor (potentiometer) — track 2
- Damaged wiring or poor connector contact to TPS track 2
- Corroded or bent connector pins
- Low/unstable 5V reference or poor ground to the sensor
- Internal sensor contamination or wear (dirty/throttled potentiometer)
- Intermittent short to voltage or ground on track 2 signal
Symptoms
- Check Engine Light (MIL) illuminated
- Reduced engine power / limp-home mode
- Erratic idle or stalling
- Poor throttle response or hesitation
- Stored related driveability fault codes
What to check
- Read freeze frame and full DTC list with a scan tool; note conditions when code set
- Visually inspect throttle body, TPS connector and wiring for damage, corrosion, pin push-out
- Check and backprobe 5V reference and ground at the sensor with ignition ON
- Measure TPS track 1 and track 2 signal voltages while slowly moving throttle
- Compare track 1 vs track 2 signals for monotonic change and correlation (no sudden jumps)
- Wiggle harness and connector while monitoring live data for intermittent faults
Signal parameters
- Typical TPS track voltages: approx. 0.5–4.5 V between closed and wide open throttle (vehicle-specific)
- 5V reference present and stable at sensor connector with ignition ON
- Signal tracks should change smoothly and proportionally to each other (no abrupt drops/spikes)
- Difference between tracks should be small and consistent; tracks should not be inverted relative to each other
- Noise on signal lines should be minimal (no rapid fluctuation or intermittent 0V/5V spikes)
Diagnostic algorithm
- Connect a compatible scan tool, record live TPS track 1 and track 2 values and freeze frame data.
- Visually inspect connector and wiring for corrosion, bent pins, broken wires or water ingress; repair as needed.
- With ignition ON (engine OFF), backprobe connector: verify stable 5V reference and good ground at sensor.
- Backprobe track 2 signal and move throttle slowly; observe voltage change. Note any dropouts, jumps or non-linear behavior.
- Compare track 2 to track 1 simultaneously. If one track is erratic or out of range while the other is normal, suspect sensor or wiring to that track.
- Perform continuity and resistance checks between TPS pins and ECU connector; check for short to battery/ground.
- Wiggle test the harness/connectors while monitoring live data to reproduce intermittent faults.
- If wiring and connectors check good and reference/ground are stable, replace the throttle position sensor (or throttle body assembly if integrated).
- After repair, clear codes and perform functional test/road test to verify proper operation and that the code does not return.
- If fault persists after sensor and wiring verified, consider ECU input circuit diagnosis or consult manufacturer technical info.
Likely causes
- Corroded/loose connector or damaged wiring to TPS track 2
- Failing throttle potentiometer (track 2 channel degraded)
- Bad 5V reference or ground at the sensor
- Wiring intermittent short when harness flexed
Fault status
Status
Throttle potentiometer (track 2) signal implausible — signal out of expected range or inconsistent with track 1. ECM may limit throttle response.
Repair difficulty: Medium
Diagnostic time: 1.0-2.5 hours
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