VW Check Engine Code
P0122 on VW
Throttle Position Sensor / Switch A Circuit Low Input
Also covers: Volkswagen, Audi, SEAT, Skoda
P0122 on VW: what makes it different
On VW/Audi (and most VAG-platform vehicles), P0122 means the throttle position signal is below the expected range. The cause is almost always carbon buildup on the throttle valve or a failing G79/G185 pedal-position sensor — both well-documented EA888/EA113/EA111 issues.
Most-affected engines
- 1.8T/2.0T EA888 (Golf, Jetta, Passat, GTI, A3, A4)
- 2.0T EA113 (older GTI/A4)
- 1.4T EA211 (Jetta, Golf)
- VR6 24V (older Passat, R32)
Common model years: 2005–present
Most likely cause on VW
Carbon buildup on the throttle valve or contaminated electronic throttle body
Known VW engine-family issues
EA888 engines (used in 2008+ GTI, Jetta, Tiguan, A3, A4, Q3) build carbon on the throttle plate and intake valves due to direct injection — there's no port injection to wash detergent across the valves. Walnut-blasting at 60–80k miles is a common preventive procedure. P0122 with a sticking pedal feel is a classic symptom.
VW-specific causes (most common first)
- Carbon buildup on the throttle plate — VAG direct-injection engines (EA888 in particular) have notorious intake-valve and throttle-body coking; the throttle plate ends up sticking partially open
- Throttle body needing adaptation (basic settings) reset via VCDS/OBDeleven after a clean or battery disconnect
- Failed J338 throttle body unit (typical $200–$450 part)
- G79 accelerator pedal sensor failure — sends bad signal to PCM, which then doesn't trust the TPS feedback
- Wiring fault or corroded T6 connector at the throttle body
VW-specific diagnostic tip
After cleaning the throttle body on any VAG vehicle, you MUST run a throttle-body adaptation (basic settings, channel 060 on older modules) using VCDS or OBDeleven. Skipping this leaves the ECU with the old learned values and P0122 will return within a drive cycle.
Symptoms drivers report
- CEL
- Limp mode
- No throttle response
- Stalling
Typical repair cost on VW
Most VW owners fix P0122 for between $0 and $500, depending on which underlying cause turns out to be at fault. Start with the most-likely cause for your vehicle — Carbon buildup on the throttle valve or contaminated electronic throttle body — before throwing parts at it.
VW P0122 FAQ
Will P0122 cause limp mode on my GTI?
Yes. VW's ETC system drops to limp mode when it can't trust the throttle signal — typical symptoms are EPC light, no-boost, and RPM limited to ~3000. After fixing the underlying cause (clean or replace throttle body, run adaptation), clear the code and the EPC light goes out after one successful key cycle.
Do I need VCDS to fix P0122 on a VW?
Strongly recommended. Cleaning or replacing the throttle body without running a basic-settings adaptation will leave the ECU calibrated for the old (dirty) values, and P0122 typically returns within 50–200 miles. OBDeleven (~$40 dongle + free adaptation channel) is the cheapest path; VCDS is the gold standard.
Related codes
Drive a different make? See the general P0122 guide for cross-vehicle causes and symptoms.
Confirm P0122 on your VW in 60 seconds
AXLY.pro is a free iPhone app that pairs with any Bluetooth OBD2 adapter to read P0122 along with freeze-frame data and live engine readings. No subscription.