P2138 on SUBARU LEGACY
Throttle/Pedal Position Sensor/Switch D/E Voltage Correlation
Methodology: Reviewed against the SAE J2012 generic DTC definition and NHTSA owner-complaint patterns, then scoped to Subaru Legacy context without treating complaints as confirmed diagnoses.
Sources: SAE/OBD-II definitions, manufacturer service information, and public reliability reports (including NHTSA where applicable).
- SAE J2012 Diagnostic Trouble Code Definitions — Generic diagnostic trouble code definition reference for P2138.
- NHTSA recalls, complaints, and manufacturer communications — Used to check public owner complaint context, recall status, and safety-related manufacturer communications by VIN or vehicle.
Limits: Guidance is informational and may not match every model-year or revision. Confirm with the official manual and diagnostics before replacing parts. For safety-critical or electrical work, use a qualified technician.
What P2138 Means on Your SUBARU LEGACY
P2138 is a diagnostic trouble code indicating: Throttle/Pedal Position Sensor/Switch D/E Voltage Correlation. This code relates to the fuel, air, emissions, or auxiliary powertrain control system. The vehicle's computer detected a condition outside normal operating parameters and stored this code.
Real SUBARU LEGACY Owner Reports
Source: NHTSA Complaints Database
"Driving southbound on hwy 17 at 60mph 11/15/2020 engine suddenly went to idle. throttle became unresponsive. check engine light illuminated. i drifted to safety off the highway. engine still idling, throttle unresponsive."
"While pressing the accelerator there was no response. the car continued at it's normal idle, but pressing on the gas gave no response. i was able to coast to a stop off the road and turn the car off and back on, which fixed the problem the first time."
"I was driving on the highway, and the car seem to loose power, luckily i noticed it, as i was able to cost over to the side of the rode. i own a carmd, and attached it to my car, it gave me code p2138 which means the throttle position sensors (2 of them) not being in agreement."
"For the second time my check engine light has come on and my car has gone into a fail safe mode while driving (eliminating the ability to accelerate). the code the computer provides is p2138, which refers to the throttle position sensors (there are two) not being in agreement."
"Car has been very slow to reduce rpms when shifting gears or when stopped (and in neutral) for the past few weeks. today, when pulling into a starbucks, the car surged forward. luckily i have a stick shift and just pushed the clutch in. after surging, the check engine light came on."
All reports filed by vehicle owners directly with the U.S. Department of Transportation.
📊 Complaint Trend by Model Year
Common Causes on SUBARU LEGACY
Based on NHTSA complaint component analysis for this vehicle.
What To Do Next
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1
Check for recalls on YOUR VIN
Go to nhtsa.gov/recalls and enter your VIN. If your vehicle is covered, repairs are free.
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2
Get a proper diagnosis
A code alone doesn't tell you the exact failed part. A diagnostic at a shop ($50–$150) pinpoints the root cause before you spend money on parts.
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3
Compare repair quotes
Get 2–3 quotes. Dealer vs. independent shop prices often differ 30–50% for the same repair.