Code
P1122
FORD
P — Powertrain
Throttle Position (TP) Sensor Circuit Intermittent Low Voltage
AI status
Completed
Completed
100%
Causes
- Damaged, corroded, or loose TP sensor connector or wiring
- Short to ground in the TP signal circuit
- Intermittent open in signal, reference (5V) or ground circuits
- Faulty throttle position sensor (potentiometer) or accelerator pedal position sensor where applicable
- Contaminated or damaged throttle body assembly
- Intermittent PCM/ECM input fault or poor PCM ground
Symptoms
- Check Engine MIL illuminated (with P1122 stored)
- Intermittent poor throttle response, hesitation or surging
- Rough idle or stalling during low-speed/idle
- Possible limp-home mode depending on vehicle
- Intermittent or inconsistent throttle position readings on a scan tool
What to check
- Retrieve freeze frame and all related codes (look for other TP or reference circuit codes)
- Visually inspect TP sensor connector and harness for damage, corrosion, bent pins or moisture
- Backprobe and monitor TP signal with an appropriate scan tool or multimeter while operating throttle
- Check TP sensor 5V reference and ground circuits for stable voltage and low resistance to chassis ground
- Wiggle the harness and connector while monitoring signal to reproduce the intermittent drop
- Measure wiring continuity from sensor connector to PCM and check for short to ground or battery
Signal parameters
- Reference voltage to sensor: approx. 5.0 V (stable)
- Signal voltage at closed throttle (typical): ~0.3–1.0 V (varies by model)
- Signal voltage at wide-open throttle: ~4.0–4.5 V (varies by model)
- Signal should change smoothly with throttle movement (no sudden drops/jumps)
- No short to ground or battery; continuity from sensor signal pin to PCM pin
Diagnostic algorithm
- Read and record all DTCs and freeze frame data. Note when code set (idle, accel, temp, voltage).
- Clear codes and attempt to reproduce while monitoring TP signal with a scan tool (live data) or multimeter. Look for intermittent low voltage events.
- Visually inspect sensor, connector, and harness for damage, corrosion, loose pins or water intrusion. Repair obvious issues.
- Backprobe sensor: verify stable 5V reference and good ground. If reference or ground is intermittent, trace and repair those circuits first.
- Measure TP signal voltage while slowly moving throttle from closed to open—confirm smooth, monotonic change and expected range.
- Wiggle harness and connector during step 5 to try to reproduce intermittent condition. If signal drops with movement, repair/replace wiring or connector.
- Check continuity and resistance between sensor pins and PCM pins. Check for short to ground or battery. Repair wiring as needed.
- If wiring and connector check good but intermittent low persists, replace the throttle position sensor (or pedal sensor where applicable).
- After repairs, clear codes and road/test to confirm permanent fix. If problem persists and wiring/sensor verified, consider PCM input fault and test/replace PCM as last resort.
Likely causes
- Loose or corroded connector at TP sensor
- Frayed wiring harness with intermittent contact (near hinge points or heat sources)
- TP sensor internal intermittency (worn wiper/contact)
- Short to chassis ground on the signal wire
- Poor/loose PCM ground or terminal
Fault status
Status
Intermittent low voltage detected on throttle position sensor signal circuit. ECM recorded sporadic drops below expected range.
Repair difficulty: Medium
Diagnostic time: 0.5-2.5 hours
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