OBD-II Diagnostic Trouble Code
P0221 — Throttle/Pedal Position Sensor/Switch B Circuit Range/Performance
P0221 means pedal or throttle position sensor B is reading in a range that does not agree with expected values or with sensor A. The circuit is electrically intact but the signal is implausible. The ECM detects this by comparing the two redundant sensors during pedal movement.
Severity 4/5
Truck-relevant
Stop within 50 mi
Severity
Stop within 50 mi
Throttle/Pedal Position Sensor/Switch B Circuit Range/Performance
Code
P0221
Category
Powertrain
Subsystem
Throttle
Truck-relevant
Yes
What this means for truckers
Stop within ~50 miles on a Cummins X15, Detroit DD15, PACCAR MX-13. Driving longer risks damaging adjacent components (turbo housing, head gasket, aftertreatment) and turning a $300 fix into a $3,000 fix.
Before you replace parts — try this first
P0221 on the Throttle system is most often worn or faulty accelerator pedal assembly — not a dead part. On commercial diesels especially, work these in order before spending money on parts:
- Confirm the symptoms. Match what your truck is doing to the Symptoms section below. If the code is set but the symptoms are not there, clear the code and re-test after a drive cycle — it may not return.
- Clean and dry the sensor connector. Water, road salt, or oil seeping into a connector is the #1 fake sensor failure. Disconnect, look for green corrosion or moisture, spray with electrical contact cleaner, dry, reseat. Many faults clear here for $0.
- Inspect the wiring harness. Trace the wire from the sensor toward the ECM — look for chafing against the engine block, melted insulation near the turbo or exhaust, or pinch points where a clamp has rubbed through.
- Test the sensor before swapping it. Most Common Causes (below) list the expected voltage or resistance range — a $20 multimeter saves a $300 sensor swap that does not fix the problem.
- Only then, replace the part. Use the OEM or a tier-1 aftermarket. Cheap sensors throw the same code in two weeks.
Symptoms
Limp mode, limited rpm, hesitation, surging or delayed response to the pedal. The truck may run normally at times and fall into reduced power while driving.
Common causes
- CommonWorn or faulty accelerator pedal assembly ($150–$500)
- CommonHigh resistance in the wiring or connector ($100–$350)
- OccasionalWater intrusion or corrosion in the pedal connector ($100–$300)
- RareECM fault ($1200–$3500)
How to fix
Graph sensor A and B voltages while sweeping the pedal and compare with specification
When to use: First step
Perform voltage drop tests on reference, ground and signal circuits
When to use: When signals disagree only slightly or intermittently
Replace the accelerator pedal assembly
When to use: When the sensor signal is erratic with good wiring
Affects most
No specific vehicle pattern found in our complaint database. This code can appear on any vehicle that supports OBD-II diagnostics.
Related
- → Browse all DTC trouble codes
- → Decode a VIN to check codes for your truck
- → Owner-operator maintenance guides
- → P0200 — Injector Circuit Malfunction
- → P0201 — Injector Circuit Malfunction - Cylinder 1
- → P0202 — Injector Circuit Malfunction - Cylinder 2
- → P0203 — Injector Circuit Malfunction - Cylinder 3
- → P0204 — Injector Circuit Malfunction - Cylinder 4
Frequently Asked Questions
Can I drive with code P0221?
Drive with caution. P0221 is severity 4 — stop within ~50 miles. Most commercial diesel codes at this severity (turbo, fuel rail, transmission solenoid) can damage adjacent expensive components if left unrepaired. Get to a service location before highway-speed loads.
How much does it cost to fix P0221 on a commercial truck?
Total repair cost ranges $100–$3500 depending on the root cause. The cheapest fix is usually the first one listed below — Worn or faulty accelerator pedal assembly — which is also the most common. On commercial trucks the cost is usually higher than passenger vehicles due to part availability and shop labor rates ($120–185/hour at most truck shops, vs $90–130 at general auto shops). DIY-capable fixes (sensors, hoses, filters) are at the low end; major component replacements (turbo actuator, high-pressure fuel pump, transmission solenoid pack) are at the high end. Always diagnose with a scan tool BEFORE replacing parts — guessing wrong on a $1,500 turbo actuator when the actual issue was a $30 boost hose is a common expensive mistake.
Will P0221 fail a DOT inspection?
P0221 is generally not a direct DOT inspection fail item by itself. Inspectors focus on safety-critical systems (brakes, steering, tires, lights, hours-of-service). However, the check engine light alone can trigger additional inspection scrutiny. Best practice: fix the code and clear it before a planned inspection.
What's the difference between P0221 and related codes?
P0221 is closely related to: P0200 (Injector Circuit Malfunction), P0201 (Injector Circuit Malfunction - Cylinder 1), P0202 (Injector Circuit Malfunction - Cylinder 2), P0203 (Injector Circuit Malfunction - Cylinder 3). These codes share the same subsystem (throttle) and often appear together. If you see this code, scan for the full code list — fixing the root cause usually clears multiple companion codes at once. If only P0221 is set without the companions, the issue is more isolated.
How do I prevent P0221 from coming back after a repair?
For P0221 (Throttle/Pedal Position Sensor/Switch B Circuit Range/Performance), prevention centers on the throttle system. Clean throttle body at 100K mile intervals. Don't let carbon build up. Avoid extended idle time.