Throttle sensor signal too low.
P0122 — also written PO122, P 0122, 0122 — is the OBD-II code for tps low input. Same code, same fix: this page covers every spelling of it.
P0122 means the ECU isn't seeing enough voltage from the throttle position sensor, usually because the sensor has a dead spot or the wiring has rubbed through. It’s a classic headache on aging Corsa and Fiesta petrol models.
P0122 is a sensors fault code, typically costing £80–£400 to put right in a UK garage.
What P0122 actually feels like to drive
- The car 'kangaroos' or jerks violently when you're light on the throttle in traffic.
- Engine suddenly drops into 'Limp Mode' with a 'Reduced Engine Power' dash message.
- A wandering or lumpy idle that feels like the car is about to stall at the lights.
- The accelerator pedal feels 'dead' for the first inch of travel before it suddenly kicks in.
- Unexpected surges in speed while you're trying to maintain a steady 30mph.
What causes P0122?
- TPS failure
- Wiring short
UK vehicles that throw P0122 most often
- Vauxhall Corsa D/E 1.2 & 1.4 (A12XER/A14XER) 2006-2018
- Ford Fiesta 1.25 & 1.4 Duratec 2008-2017
- Volkswagen Polo 1.2 12v (AZQ/BME engines) 2002-2009
- Peugeot 207/208 1.4 VTi (EP3 engine) 2007-2015
- Honda Civic 1.8 i-VTEC (R18A) 2006-2012
- Fiat 500 1.2 Fire engine 2008-2020
How P0122 is fixed
- Replace TPS
- Inspect wiring
The P0122 misdiagnosis that wastes money
I see so many DIYers and even some junior lads chucking a brand new throttle body at this immediately. On many modern Vauxhalls and Fords, you can't just swap the sensor; it’s a sealed unit, so you’re looking at £250 for the part alone. But half the time, it's actually just 'green death' (corrosion) in the multi-plug or a chafed wire where the loom rubs against the gearbox casing. I've seen blokes spend £400 on a genuine Bosch unit only for the light to pop back on before they've even finished their brew because the wiring was the real culprit.
What a UK garage should charge for P0122
For a basic diagnostic plug-in and 30 minutes of loom checking, expect to pay £60-£90 at an indie. If the sensor is separate (common on older Japanese cars), the part is about £40. But for most Euro cars where it's a built-in TPS, a quality OE-spec replacement (Hella, Pierburg, or VDO) runs between £140 and £220. With an hour's labour to fit and perform the 'throttle relearn' procedure, you're looking at £250-£350 total. Main dealers will easily double that for the exact same part in a branded box.
P0122 repair cost in the UK
Most P0122 repairs land between £80–£400 including parts and labour. The spread is wide because the cheap fix (a sensor, a hose, a leak) and the expensive fix (a major component) throw the same code — which is why a proper diagnosis before parts are bought saves the most money.
Bob's tip on P0122
If a garage tells you that you need a new throttle body right away, ask them if they've done a 'sweep test' on the TPS with an oscilloscope. A basic code reader only shows a snapshot. You want to know if there's a specific 'dead spot' in the sensor's voltage range. Also, check your floor mats! I’m not joking—I once had a customer with a P0122 because a thick rubber mat from Halfords was wedged under the pedal, preventing the sensor from returning to its base voltage, which confused the ECU into thinking the signal was implausibly low.
Can you drive with P0122?
Drivable.
Urgency: medium.