Diesel Trouble Codes

P0221 — Throttle/Pedal Position Sensor/Switch B Circuit Range/Performance (5.9 Cummins Common Rail)

Throttle/Pedal Position Sensor/Switch B Circuit Range/Performance

Updated September 2, 2026

What it means

The engine control module has detected that the signal from throttle/pedal position sensor/switch B is outside the expected range or is not performing as expected. On the 5.9L Cummins Common Rail 2003-2007 Dodge Ram 2500/3500 ISB, the accelerator pedal position sensor (APPS) is still used and P0121/P0122/P0221-type faults remain common per platform facts.12

Most likely causes

  1. APPS sensor internal wear or out-of-range voltage on sensor B — APPS signal drift or internal failure causing range/performance error for sensor B.12
  2. APPS wiring/connector corrosion, chafing, or poor ground causing erratic sensor B signal — Intermittent or noisy signal to ECM from sensor B circuit.12
  3. ECM pedal input processing anomaly for sensor B — ECM detects sensor B performance outside expected range despite wiring integrity.1

How to diagnose

  1. Verify code and freeze frame; confirm P0221 is present on 5.9 Cummins Common Rail 2003-2007 with APPS still used.
  2. Inspect APPS connector and wiring for corrosion, moisture, chafing, and secure pin engagement; check harness routing near pedal assembly.
  3. Monitor live APPS sensor A and sensor B voltages with a scan tool while slowly pressing pedal from idle to wide open; look for smooth, proportional change and expected correlation between A and B.
  4. Check reference voltage and ground supplies to APPS per service information; verify no voltage drop or intermittent opens during wiggle test of harness.
  5. If voltages are out of range or erratic, replace APPS assembly; clear codes and retest pedal sweep for consistent sensor B performance.

Parts and tools you may need

Rough cost and difficulty

Parts and labor vary by region and shop; APPS replacement is typically moderate cost compared with diagnostic time.

When to see a pro

If pedal signal remains erratic after APPS and wiring checks, have a diesel technician evaluate ECM inputs and harness integrity to avoid misdiagnosis.

Sources

  1. Curated DTC seed — 5.9 Cummins Common Rail (curated) ↩︎ ↩︎ ↩︎ ↩︎

  2. Curated DTC seed — 5.9 Cummins Common Rail (curated) ↩︎ ↩︎ ↩︎