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 October 15, 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.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

• Scan tool with live data
• Digital multimeter
• APPS assembly (pedal position sensor)
• Dielectric grease
• Basic hand tools

Tools you’ll need

• OBD-II scan tool — Reads P0221 and live APPS sensor A/B voltages during a pedal sweep to confirm out-of-range or erratic sensor B behavior.
• Digital multimeter — Checks APPS reference voltage, ground integrity, and sensor B signal voltage at the connector to find wiring faults or out-of-range readings.
• Back-probe kit — Allows safe measurement of APPS sensor B signal while wiggling the harness to detect intermittent opens or corrosion without damaging terminals.
• Inspection mirror and flashlight — Provides clear view of the APPS connector and harness routing near the pedal assembly for corrosion, moisture, and chafing inspection.

Rough cost and difficulty

Typical US independent-shop figures; labor runs about $120–$180 per hour (dealers charge more). Confirm the diagnosis before buying parts.

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.

Check for recalls

Recalls are tied to your truck’s VIN, so check yours directly: enter the VIN at NHTSA’s recall lookup. Open safety recalls are repaired free at a dealer.

Sources