Ford Check Engine Code
P2138 on Ford
Throttle / Pedal Position Sensor D / E Voltage Correlation
Also covers: Lincoln, Mercury
P2138 on Ford: what makes it different
P2138 signals a voltage correlation mismatch between the two throttle/accelerator pedal position sensor circuits in Ford's electronic throttle control (ETC) system, used across most drive-by-wire Ford models since the mid-2000s.
Most-affected engines
- Duratec 2.0L/2.5L I4 (Focus, Fusion)
- Duratec 3.0L/3.5L V6 (Escape, Edge)
- EcoBoost 1.6L/2.0L (Escape, Fusion)
Common model years: 2008–2016
Most likely cause on Ford
A worn or internally degraded accelerator pedal position (APP) sensor assembly causing the two internal sensor signals to drift apart.
Known Ford engine-family issues
Ford's APP sensor assemblies are a known wear item over high mileage, and intermittent voltage correlation faults are commonly traced back to the pedal sensor itself rather than the throttle body.
Ford-specific causes (most common first)
- Worn APP sensor assembly under the pedal producing mismatched sensor A/B voltages
- Wiring harness rubbing or chafing near the pedal bracket or floor pan
- Corroded or loose APP sensor connector pins
- Electronic throttle body sensor drift or contamination
- Low or fluctuating system voltage from a weak battery or alternator affecting sensor readings
Ford-specific diagnostic tip
With the key on, watch APP sensor A and B live voltage on a scan tool while slowly depressing the pedal through its full travel — a healthy pair moves in a smooth, proportional ratio; a lag or jump in one signal points to the pedal sensor, not the throttle body.
Symptoms drivers report
- Check engine light
- Reduced engine power / limp mode
- No throttle response
- Stalling
Typical repair cost on Ford
Most Ford owners fix P2138 for between $150 and $450, depending on which underlying cause turns out to be at fault. Start with the most-likely cause for your vehicle — A worn or internally degraded accelerator pedal position (APP) sensor assembly causing the two internal sensor signals to drift apart. — before throwing parts at it.
Ford P2138 FAQ
Does P2138 mean I need a new throttle body on my Ford?
Not usually. On most Fords this code points to the accelerator pedal sensor assembly rather than the throttle body itself, so check pedal sensor voltages first before replacing the throttle body.
Can a weak battery cause P2138 on a Ford?
Yes, low or unstable system voltage can cause the pedal position sensors to report inconsistent readings, triggering a correlation fault even if the sensor itself is fine.
Related codes
Drive a different make? See the general P2138 guide for cross-vehicle causes and symptoms.
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