P2122: Throttle/Pedal Position Sensor/Switch D Circuit Low
A generic powertrain (engine and transmission) trouble code, same meaning on every brand.
Surface streets only - reduced power is survivable in town, but a pedal fault can worsen to idle-only without warning, and the highway is the wrong place to find out.
Symptoms
- Reduced power warning
- Pedal feels dead or delayed
- Idle-only running if the second sensor also reads implausibly
- Code sets immediately at key-on when the fault is hard
Likely causes, most common first
- Accelerator pedal position sensor D failed
- Open or short in the sensor wiring
- Corroded or backed-out connector pin
- Loss of the 5-volt reference feeding the sensor
Read P2122 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
P2122 says the voltage from accelerator pedal sensor D dropped below the plausible window - the electrical signature of an open circuit, a short to ground, or a dead sensor track. Drive-by-wire pedals carry two sensors reading the same motion on different scales; the computer compares them constantly, and this code names the D channel specifically.
The pedal is sold as an assembly and replacement is usually a fifteen-minute job, which tempts people to skip diagnosis. Resist once: check the 5-volt reference at the pedal connector first. That reference is often shared with other sensors, and a chafed wire elsewhere can drag it down - in which case a new pedal changes nothing. Reference present, signal absent: pedal. Reference absent: wiring, and the pedal was never guilty.
Repair options and cost
Typical US independent-shop ranges, parts and labor. Dealers run higher; regional labor rates vary.
Owner reports mentioning P2122
“The contact owns a 2021 GMC Acadia. The contact stated while driving 50 MPH, the vehicle suddenly decelerated to 35 MPH. The vehicle stalled, and the "Steering Assistance Reduced" message was displayed. The vehicle was restarted. The vehicle was taken to the local dealer the following day, where it was diagnosed that the accelerator pedal and terminal connector were bent. The dealer retrieved DTC codes: P2138, and P2122. The vehicle was repaired. The manufacturer was notified of the failure. The approximate failure mileage was 27,792.”2021 GMC Acadia · Jul 2024 · 27,792 mi
“Code p2128 Code p2122 Have replaced TPS, THROTTLE BODY, ACCELERATOR PEDAL (Ã-3) AND bypassed connectors WITH DIRECT WIRING from ACCELERATOR PEDAL TO ECM Continue to get codes with CHECK ENGINE LIGHT with DECREASED ENGINE POWER, CHECK STABILITRAK, and STABILITRAK DISABLED. HAVE TO CLEAR CODES WITH BLUEDRIVER MULTIPLE TIMES EVEN WHILE DRIVING SHORT DISTANCES AND SOMETIMES ON START UP.”2007 Chevrolet Avalanche · Jul 2024
“Throttle body sensor, throttle body injector, and acceleration pedal are failing. I was in traffic and my car went into limp mode because of a code P2122 which is the throttle body sensor. My car did not want to go faster than 10 miles an hour.”2019 Jeep Renegade · Dec 2023
Show 7 more owner reports
“The check engine light came on and lost power and fuel. Took it in mechanic shop pulled up code p2122 throttle/ pedal sensor failure”2017 Jeep Renegade · Jul 2023
“Constant random recurrence of error codes P2122 and P2138 (either together or on their own) which results in the car switching to low power mode, with very low acceleration which makes it very dangerous to merge into traffic, pull out of stops, red lights, etc. Technically supposed to require changing the throttle pedal sensor, but changing it does not solve the issue, which is electrical. This is a known issue for GM cars.”2004 Saab 9-3 · Jun 2022
“Driving along and Reduced Engine Power warning message came on said can not go above 20 mph but yet car still could be accelerated above 20mph. Pulled over when could. Stopped car and turned it off and on. message gone but engine warning light still on. OBD2 stated P2122 error. Upon reviewing internet there are class action lawsuits going on because can create a very dangerous scenario if car suddenly stops in the middle of the highway.”2016 Chevrolet Malibu · Feb 2022
“The P2122 OBD-II trouble, or fault, code means that the vehicle's on-board computer has detected low voltage in the throttle position sensor (TPS), which is usually below 0.17 volts. The battery is also at 8.3 volts indicating a potential short somewhere and potentially a faulty alternator. This is not what you want while driving a vehicle.”2019 Jeep Cherokee · Sep 2021
“Service stabilitrak message displayed and reduced engine power to 0 mph while driving. Throttle body, Accelerator pedal position sensor (whole pedal assembly), and ecm replaced. Issue continues. P2138, P2122, P2127 codes present. Stonebriar chevrolet incompetent to resolve.”2010 Chevrolet Impala · Aug 2021
“During any type of moisture ie (fog, rain) vehicle goes into reduced engine power mode codes from the ecm p2122 and p2138 both relating to app. First time it happened was in rain storm in motion, app pedal was replaced with new oem part but the problem persists. I suspect water intrusion from wiper cowling affecting electric harness. This problem does not exist during dry season. After many hours of online research I have found that this is a widespread problem in chevrolet vehicles.”2016 Chevrolet Colorado · Jan 2021 · 126,000 mi
“2016 sonata with 103,000 mile. Increased oil consumption. Regular full synthetic oil changes have been followed. The engine burns out oil well before oil change is due. Oil lamp flickers. Mechanic states oils is burning up and released through exhaust therefore no leaks detected. 2nd issue: p2122 check engine code. Diagnostics reveals pedal acceleration sensor faulty. Part was $202. Not sure if this is misdiagnosed and related to sluggish engine due to oil consumption.”2016 Hyundai Sonata · Aug 2020 · 103,000 mi
Cars that report P2122 most often
Based on mentions of this code in NHTSA owner complaints.
Frequently asked questions
Can I drive with P2122?
Surface streets only - reduced power is survivable in town, but a pedal fault can worsen to idle-only without warning, and the highway is the wrong place to find out.
How much does it cost to fix P2122?
Typical US repair costs range from $60 for the simplest fix (accelerator pedal assembly) to $450 in the worst case. The right number depends on which cause your car has - see the causes list.
Related codes
The codes closest to P2122. 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.