P0121: How to Diagnose & Fix — Throttle/Pedal Position Sensor Circuit Range/Performance
12 vehicles · 6 makes · $50-$1,800 repair
How to diagnose and fix P0121: most-reported vehicles
Ranked by owner reports. Each card gives the symptoms, how to confirm the cause, the fix, parts and sources for that vehicle.
Volvo S40 · 2004–2011
The electronic throttle module (ETM) on S40/V50 models with the 2.4L non-turbo (B5244S) and early T5 engines fails due to internal solder joint cracking from thermal cycling. The ETM controls the throttle blade electronically, and when it fails, the engine enters limp mode with severely limited power or refuses to rev above idle. The issue primarily affects pre-2008 models, as Volvo updated the ETM design. Volvo issued an extended warranty program for the ETM on affected models. The ETM failure is distinct from the P2 platform (older S60/V70) ETM issue but has similar symptoms.
Common Symptoms
- Check engine light with throttle position codes (P0121, P0122, P0123)
- Engine enters limp mode with limited power
- Engine won't rev above 2,000-2,500 RPM
- Hesitation or surging during acceleration
- Engine stalling at idle
How to Fix
Replace the electronic throttle module (ETM). Updated Volvo part 30711552 or 31216665 depending on engine type. Bosch aftermarket units are also available. Clear fault codes after replacement and perform throttle body adaptation using VIDA diagnostic tool. Check for Volvo extended warranty coverage, which covered the ETM replacement for up to 10 years on some model years. The repair is straightforward - the ETM bolts to the intake manifold and can be replaced in under an hour.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Genuine Volvo 31216327 non-turbo five-cylinder throttle body
replace a scan-data-confirmed internal throttle-body failure on the non-turbo gasoline branch Fitment/availability: Applicable Volvo S40 P1 non-turbo five-cylinder gasoline branch using OE 31216327; confirm VIN, engine code and installed…
- Genuine Volvo 30711552 T5 fuel-injection throttle body
replace a scan-data-confirmed internal T5 throttle-body failure after boost-control and wiring faults are excluded Fitment/availability: Applicable 2004.5-2011 Volvo S40 P1 T5 gasoline branch using OE 30711552; confirm VIN, B5254T engine…
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Ford Transit Connect · 2014–2021
Owners report sudden reduced power, poor throttle response, and limp-home behavior due to electronic throttle body contamination/wear or throttle actuator control faults. The issue can be intermittent and may clear after a key cycle, then recur, which is a common pattern in NHTSA complaints and owner reports. It often sets throttle/ETC-related DTCs and can be triggered by carbon buildup or failing throttle position sensing.
Common Symptoms
- Reduced engine power message/limp mode
- Poor throttle response or no acceleration
- Stalling or near-stalling at idle
- Intermittent issue resolved by key cycle
- Check engine light on
How to Fix
Confirm DTCs and perform throttle body inspection/cleaning if contamination is present; if faults persist, replace the throttle body assembly and perform the required idle/throttle relearn procedure. Inspect related wiring/connectors and verify PCM updates if applicable.
Sources for this issue (1)
Cadillac Escalade · 2007–2014
GMT900 Escalades commonly throw 'Service StabiliTrak' and 'Service Traction Control' together with a reduced-engine-power event, and owners chase it for months because three unrelated root causes present identically. The most common is the electronic throttle body - carbon buildup on the blade and a worn throttle position sensor track make the two APP/TPS signals disagree, the PCM defaults to limp mode, and StabiliTrak disables itself because it can no longer command torque reduction. The second is the brake pressure sensor or the EBCM internally, which sets a chassis code and disables ESC without any engine symptom. The third is a weak battery or corroded ground causing a low-voltage brownout that trips every chassis module at once. CarComplaints lists 'Stabiltrak Light On' as the #3 problem on the 2007 Escalade at an average of $1,800 and 75,000 miles, and the 2007 model year carries 41 NHTSA engine complaints alongside a large ESC-related brakes group on 2011.
Common Symptoms
- Service StabiliTrak and Service Traction Control messages appear together
- Engine Power Reduced message with the vehicle limited to low speed
- Warning lights clear after an ignition cycle then return under load
- ABS and traction control lights on with normal braking otherwise
- Rough or surging idle after the throttle fault
How to Fix
Scan for chassis codes, not just powertrain codes - a generic OBD2 reader that only sees P-codes will miss the C-codes that actually identify the fault. C0561 alone means the module disabled itself because something else failed and is not the root cause; look for the code that set alongside it. If the event includes reduced engine power with a throttle-correlation code, remove and clean the throttle body with throttle-body cleaner and a soft cloth (never scrape the bore coating), then perform the idle relearn; if the fault returns, replace the throttle body, roughly $250-$450 installed. Before any of that, load-test the battery and clean the battery terminals and the engine-to-frame grounds - low voltage is the single most common cause of a multi-module StabiliTrak complaint and costs nothing to rule out. If the codes point at brake pressure sensing, the sensor is serviceable on many of these and is far cheaper than the EBCM; only condemn the EBCM after the sensor and its wiring check out. EBCM replacement or rebuild runs about $500-$1,200.
Sources for this issue (2)
Volvo S70 · 1999–2000
Pontiac G6 · 2006–2010
Find P0121 by make
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P0121 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0121 mean?
P0121 stands for "Throttle/Pedal Position Sensor Circuit Range/Performance." This code means the throttle position (or accelerator pedal position) sensor's signal does not match what the computer expects compared with other inputs like airflow, RPM, and the second throttle/pedal sensor. The sensor tells the computer how far the throttle or pedal is open; when its range or performance is off, the computer can't trust how much power you're requesting. You may notice hesitation, surging, poor acceleration, rough idle, or the vehicle dropping into a reduced-power 'limp' mode. It indicates an out-of-range or implausible signal rather than a complete loss of signal.
What are the most common causes of P0121?
The most common causes of P0121 are: Worn or failing throttle position sensor, Dirty or carboned-up throttle body affecting plate position, Damaged, frayed, or shorted sensor wiring, Corroded or loose sensor connector, Poor sensor ground or reference voltage, Faulty throttle body / electronic throttle actuator, Mismatch between the two throttle or pedal sensor signals. The specific cause varies by vehicle.
How much does it cost to fix P0121?
Repair costs for P0121 range from $50 to $1,800, depending on the vehicle and root cause.
Which vehicles are affected by P0121?
Au7o has documented P0121 across 12 vehicle models from 6 manufacturers: Cadillac, Chevrolet, Ford, Jeep, Pontiac, Volvo.
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.