Code
P1221
JAGUAR
P — Powertrain
Pedal Demand Sensor B Circuit Range Performance
AI status
Completed
Completed
100%
Causes
- Open or shorted wiring in Pedal Demand Sensor B circuit
- Poor, corroded or loose connector at the pedal position sensor or wiring harness
- Faulty accelerator pedal position sensor (Pedal Demand Sensor B element)
- Contamination or water ingress at connector or pedal assembly
- Incorrect reference voltage or ground (powertrain control module side)
- Intermittent internal sensor fault or mechanical damage inside pedal assembly
Symptoms
- Check Engine Light (MIL) illuminated
- Possible reduced engine power or limp mode
- Poor or delayed throttle response
- Unstable idle or hesitation under throttle
- Intermittent loss of drive or sudden changes in engine response
What to check
- Read and record freeze frame and MIL status with a diagnostic scan tool
- View live data for Pedal Demand Sensor A and B while operating pedal
- Visually inspect pedal connector and wiring for damage, corrosion, or moisture
- Wiggle test wiring harness and connector while watching live data for intermittent changes
- Backprobe connector to verify reference voltage (typically ~5 V) and signal voltage ranges
- Check continuity and resistance to ground on the sensor ground circuit
Signal parameters
- Reference (supply) voltage: typically ~5.0 V (verify vehicle-specific value)
- Sensor output voltage range: typically ~0.5 V (closed) to ~4.5 V (fully depressed) — verify exact spec
- Sensor B should track Sensor A with a consistent relationship; rapid divergence or values outside spec triggers the code
- No more than ~50–200 mV unexpected offset between A and B under the same pedal position (vehicle-specific tolerance)
Diagnostic algorithm
- Use a scan tool to confirm P1221 and review freeze frame and live data. Clear the code and attempt to re-create; note if fault is steady or intermittent.
- With ignition on (engine off), monitor Pedal Demand Sensor A and B voltages. Slowly depress pedal and ensure both signals change smoothly and correlate; note any dead zones, spikes, or out-of-range voltages.
- Inspect the pedal connector and wiring harness for physical damage, corrosion or moisture. Repair or clean as needed.
- Backprobe the pedal connector: verify reference supply (≈5 V) and ground are present and stable. Measure signal at connector while operating pedal.
- If reference or ground are missing/unstable, trace and repair harness, grounds, or ECM connector as required.
- Perform continuity/resistance checks from pedal connector to the ECM connector for signal, reference and ground circuits to find opens or high resistance.
- Wiggle the wiring and connector while watching live data to find intermittent faults. Repair harness or secure routing if fault appears under movement.
- If wiring and connectors test good but sensor B output remains out of range or does not follow sensor A, replace the accelerator pedal assembly (or the pedal sensor module per factory procedure).
- After repair, clear codes and road test to confirm the fault does not return. If code persists after sensor replacement, investigate ECM input circuitry or perform ECU testing/replacement per factory guidance.
Likely causes
- Damaged/frayed wire where harness passes through firewall or near pedal
- Corroded terminal or pushed-out pin at pedal connector
- Failed pedal assembly (sensor element B)
- Moisture ingress into pedal connector causing intermittent shorts
- Loose ground or poor chassis/ECM ground connection affecting sensor reference
Fault status
Status
P1221 - Pedal Demand Sensor B Circuit Range/Performance. Pedal sensor channel B output is outside expected range or not correlating with channel A. Possible wiring, connector, sensor or ECM input fault.
Repair difficulty: Medium
Diagnostic time: 1.0-2.0 hours
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