OBD-II Diagnostic Trouble Code
P2128 — Throttle/Pedal Position Sensor/Switch E Circuit High Input
P2128 means the accelerator pedal position sensor E signal is above the maximum voltage the ECM expects. An open sensor ground or a signal wire shorted to voltage are the usual reasons.
Severity 4/5
Truck-relevant
Stop within 50 mi
Severity
Stop within 50 mi
Throttle/Pedal Position Sensor/Switch E Circuit High Input
Code
P2128
Category
Powertrain
Subsystem
Throttle
Truck-relevant
Yes
What this means for truckers
P2128 — see existing entry.
Before you replace parts — try this first
P2128 on the Throttle system is most often open or corroded sensor ground — 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
The check-engine light is on and the engine typically goes to idle or reduced power, ignoring part or all of the pedal input.
Common causes
- CommonOpen or corroded sensor ground ($80–$300)
- CommonFailed pedal sensor ($180–$550)
- OccasionalSignal shorted to reference or battery voltage ($100–$400)
- RareECM fault ($800–$2500)
How to fix
Check sensor ground continuity and voltage drop
When to use: First check
Unplug the sensor and see whether the signal stays high to find a harness short
When to use: To separate wiring from sensor faults
Replace the pedal assembly
When to use: When wiring tests good
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
- → P2100 — Throttle Actuator Control Motor Circuit/Open
- → P2101 — Throttle Actuator Control Motor Circuit Range/Performance
- → P2120 — Throttle/Pedal Position Sensor/Switch D Circuit
- → P2127 — Throttle/Pedal Position Sensor/Switch E Circuit Low Input
- → P2138 — Throttle/Pedal Position Sensor/Switch D/E Voltage Correlation
Frequently Asked Questions
Can I drive with code P2128?
Drive with caution. P2128 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 P2128 on a commercial truck?
Total repair cost ranges $80–$2500 depending on the root cause. The cheapest fix is usually the first one listed below — Open or corroded sensor ground — 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 P2128 fail a DOT inspection?
P2128 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 P2128 and related codes?
P2128 is closely related to: P2100 (Throttle Actuator Control Motor Circuit/Open), P2101 (Throttle Actuator Control Motor Circuit Range/Performance), P2120 (Throttle/Pedal Position Sensor/Switch D Circuit), P2127 (Throttle/Pedal Position Sensor/Switch E Circuit Low Input). 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 P2128 is set without the companions, the issue is more isolated.
How do I prevent P2128 from coming back after a repair?
For P2128 (Throttle/Pedal Position Sensor/Switch E Circuit High Input), prevention centers on the throttle system. Clean throttle body at 100K mile intervals. Don't let carbon build up. Avoid extended idle time.