Code
P1122
JAGUAR
P — Powertrain
Pedal Position Sensor A Circuit Low Input
Views:
UK: 34
EN: 67
RU: 41
AI status
Completed
Completed
100%
Causes
- Damaged or shorted wiring in pedal sensor A circuit (short to ground)
- Corroded, loose, or damaged connector at accelerator pedal or ECU
- Failed pedal position sensor (internal short or open)
- Loss of 5V reference or poor ground to the sensor circuit
- Water ingress or contamination in pedal assembly
- Intermittent ECU input fault (rare)
Symptoms
- Check Engine Light (MIL) illuminated
- Reduced engine power or limp-home mode
- Poor or no throttle response to accelerator pedal
- Hesitation or delayed acceleration
- Stored freeze frame data showing low pedal voltage
What to check
- Read stored/active DTCs and freeze frame data with a scan tool
- Monitor live pedal position A and B sensor values while operating the pedal
- Visually inspect harness, pins and connector at pedal and ECU for corrosion, damage or water
- Backprobe connector with key ON engine OFF and measure voltages (signal, 5V reference, ground)
- Wiggle test harness while monitoring sensor voltage to spot intermittent faults
- Check continuity and resistance between pedal sensor signal and ECU pin with connector disconnected
Signal parameters
- Sensor uses a 5 V reference supply from the ECU and returns a 0–5 V position signal
- Typical operating range (generic): ≈0.5–1.5 V at rest, increasing up to ≈3.5–4.5 V at full pedal travel
- Low-input fault threshold: signal significantly below expected minimum (often
- Sensor A and B should vary smoothly with pedal travel and not be identical (redundant but slightly offset)
Diagnostic algorithm
- Connect a scan tool, record DTCs and freeze frame data. Note conditions when code set.
- Clear codes and attempt to reproduce; monitor live data for Pedal Position Sensor A and B.
- Visually inspect pedal connector, pins and wiring for damage, corrosion, or moisture. Repair as needed.
- With ignition ON (engine OFF) backprobe the pedal A signal wire: verify 5V reference present and reliable ground at pedal connector.
- Measure signal voltage at rest and while moving pedal. If voltage is low or erratic, perform wiggle test to isolate intermittent wiring faults.
- If wiring and connectors are good, disconnect pedal assembly and measure continuity/resistance from pedal signal to ECU pin. Repair broken wires or poor crimps.
- If wiring/connector check out and signal still low, replace the accelerator pedal assembly (sensor).
- After repair, clear codes and road-test to confirm normal pedal voltage behavior and no reoccurrence. If fault persists, consider ECU input circuit diagnosis or replacement.
Likely causes
- Wiring/connector damage or corrosion in the pedal harness
- Failed pedal position sensor (accelerator pedal assembly)
- Faulty 5V reference or ground at the sensor
- Intermittent connection due to vibration or contamination
- ECU input circuit fault (least likely)
Fault status
Status
Pedal Position Sensor A Circuit Low Input — ECU detected abnormally low voltage on the accelerator pedal A signal; limp mode or reduced power may be enacted.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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