P2138: Throttle/Pedal Position Sensor/Switch D/E Voltage Correlation
A generic powertrain (engine and transmission) trouble code, same meaning on every brand.
Drive gently to a shop - reduced power mode is normal with this fault.
Symptoms
- Reduced power mode
- Pedal feels dead or inconsistent
- Engine stuck at idle speed
Likely causes, most common first
- Accelerator pedal position sensor failing
- Connector or wiring fault at the pedal
- Water damage in the footwell harness
- Poor ground on the pedal circuit
Read P2138 yourself before paying for diagnosis
A basic Bluetooth OBD-II scanner ($20-40) plugs into the port under the dashboard and shows this code with live sensor data on your phone - useful both for confirming the fix and for talking to a shop from an informed position.
What is going on and how it gets diagnosed
P2138 is the pedal-side version of P2135: the two sensors inside the accelerator pedal no longer agree. The pedal assembly contains its own redundant pair for the same safety reason as the throttle body, and the computer treats disagreement as untrustworthy input.
The pedal sensor is normally sold as a complete assembly, so the repair is straightforward once the diagnosis is confirmed. Before ordering, check the footwell harness for water damage - a leaking windscreen seal or heater core soaks that area, and corrosion there mimics a failed pedal exactly.
Repair options and cost
Typical US independent-shop ranges, parts and labor. Dealers run higher; regional labor rates vary.
Owner reports mentioning P2138
“My Acadia went into limp Mode displaying low power mode on the screen and wouldn't start for a couple days after. Lights started illuminating on the dash as abs, traction control, and stanilitrack, then check engine light came on and my gmc app displayed code p2138. I have had since low power and extremely high gas consumption.”2017 GMC Acadia · Jul 2026
“For no apparent reason the truck goes into "low power mode" and gives off code p2138 often happens around 30-35 mph. Have had it happen to me also around 45 mph also. I have replaced sensors and parts to which a month or so goes by and it happens again.”2015 GMC Sierra 1500 · May 2026
“While driving on the highway at 60 mph, warning on dash came on saying "engine power reduced" and drop down speed to around 25 mph and I could not accelerate more than 25 mph on the highway which could have caused an accident because of the traffic flow behind me. I put a code scanner under the dash and it read code P2138, Throttle pedal position sensor switch.”2011 Buick Regal · May 2026
Show 7 more owner reports
“While traveling on vacation April 15, my 2025 F150 truck suffered a total loss of forward momentum on the highway and in city of Los Angeles -a severe safety failure. The repairing Ford dealership, diagnosed a factory-born "OPEN" in the main wiring harness (#14A005) behind the dash (DTCs P2128/P2138). To rectify this assembly-line defect, the dealership had to completely remove the dashboard (Instrument Panel). As an experienced truck owner, I know that an invasive repair of this magnitude on a brand-new vehicle significantly increases the risk of long-term electrical issues and permanent dashboard rattles. My confidence in this specific vehicle has been severely compromised.”2025 Ford F-150 · Apr 2026
“P2138 code. Gas pedal stops responding to inputs. Car goes into limp mode and managed to get car off the road. Shut off and waited 5 minutes, restarted and it works again. Associated P0500 code also present. First time this has happened on this car.”2005 Subaru Outback · Mar 2026
“The way the accelerator pedal sensor is positioned allows for water infiltration from wet carpet / tracked in snow and water. The component is available for inspection upon request. Once sufficiently saturated the sensor fails, and ceases function DURING VEHICLE MOVEMENT. The problem is reproducible but has not been confirmed as a pattern of failure by the dealership. As far as my recollection, the manufacturer hasn’t inspected the part. P2138 is the associated check engine code and the vehicle enters limp mode DURING TRAVEL. The check engine light (and subsequent problems) first appeared while in traffic on 2/10/2026.”2024 Toyota Prius · Feb 2026
“UNKNOWN While I'm driving my car will lose power and go into reduced engine power mode and slows me down to a crawl. I've almost been hit in the back many times for to this. The coffee is P2138”2016 Chevrolet Malibu · Dec 2025
“I was on the freeway when the check engine light came on with an alert I couldn't read in time before it disappeared. Then the gas pedal stopped working. I got to a safe place and shut off the car. My brother-in-law then drove the car the 5 miles back home on local roads - he videod the throttle ramping up when he was either braking or the foot wasn't on the gas pedal, which happened 4-5 times. Subaru service pulled fault code P2138.”2014 Subaru Forester · Jul 2025
“Reviving the p2138 code for throttle/accelerator sensor. Still getting code after replacing 3 accelerator peddles. Possible manufacture issue with wiring that water gets into connectors shorting out that system”2012 Chevrolet Sonic · Jul 2025
“Vehicle producing code P2138 then goes into limp mode stating to service stability, traction control off and engine reduced power. Replaced Throttle Body and Acceleration Pedal Position Sensor and error was still present.”2012 GMC Acadia · May 2025
Cars that report P2138 most often
Based on mentions of this code in NHTSA owner complaints.
Frequently asked questions
Can I drive with P2138?
Drive gently to a shop - reduced power mode is normal with this fault.
How much does it cost to fix P2138?
Typical US repair costs range from $80 for the simplest fix (accelerator pedal assembly) to $700 in the worst case. The right number depends on which cause your car has - see the causes list.
Related codes
The codes closest to P2138. They often appear together, and telling them apart is usually what narrows the diagnosis.
Definition per SAE J2012 standard nomenclature. Symptoms, causes and costs are editorial guidance - always confirm with a diagnosis of your specific vehicle.