Pedal sensor voltages don't match.
P2138 — also written P2138, P 2138, 2138 — is the OBD-II code for throttle/pedal position sensor voltage correlation. Same code, same fix: this page covers every spelling of it.
This is the ECU getting two different stories from the sensors in your accelerator pedal and having a panic attack because it doesn't know how much throttle you're actually asking for. It's a classic plague on Vauxhalls and Nissans where the internal tracks in the pedal assembly pack up.
P2138 is a sensors fault code, typically costing £150–£600 to put right in a UK garage.
What P2138 actually feels like to drive
- The car suddenly drops into 'Limp Mode' with a 'Service ESC' or 'Engine Power Reduced' message.
- The accelerator pedal feels completely dead, like it's disconnected from the engine.
- The car 'hiccups' or jerks violently for a split second while you're cruising at motorway speeds.
- Erratic idling where the revs jump up to 1,500rpm on their own to keep the engine from stalling.
- The fault clears if you turn the ignition off and back on, but comes back the moment you hit a bump.
What causes P2138?
- Failed pedal assembly
- Wiring
UK vehicles that throw P2138 most often
- Vauxhall Astra J / GTC 1.4 & 1.6 Turbo (2009-2015) - Very common.
- Vauxhall Insignia A 2.0 CDTi (A20DTH) 2008-2017.
- Nissan Qashqai J10 1.5 dCi (2007-2013).
- Chevrolet Aveo / Cruze 1.4 (2011-2015).
- Ford Transit Custom 2.2 TDCi (2012-2016).
- Honda Civic 2.2 i-CTDi (2006-2011) - Often wiring related.
How P2138 is fixed
- Pedal assembly replacement
The P2138 misdiagnosis that wastes money
The biggest mistake I see "parts cannons" making with P2138 is blindly replacing the throttle body on the engine. They see 'Throttle' in the description and drop £300 on a new unit, but this code is almost always about the pedal under your foot. I’ve also seen lads swap the pedal only for the code to return because the real culprit was water ingress in the fuse box or a corroded multi-plug near the bulkhead. On Vauxhalls, especially, it’s often a poor connection at the J2 connector, not the pedal itself.
What a UK garage should charge for P2138
At an indie like mine, you’re looking at £50-£80 for the initial diagnostic. A genuine Hella or Bosch pedal assembly usually sits between £120 and £220 depending on the car. Labour is a doddle—usually 30 to 60 minutes—so another £60. All in, you’re looking at £250-£350. If you go to a Vauxhall or Nissan main dealer, they’ll sting you closer to £500 or £600 once they’ve added their 'premium' labour rates and VAT on top.
P2138 repair cost in the UK
Most P2138 repairs land between £150–£600 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 P2138
Before you let a garage bill you for a new pedal, tell them you want a 'live data sweep' test. A decent tech will plug in their Snapon or Autel tool and watch the two pedal tracks on a graph. They should move perfectly in sync; if one drops out while the other rises, it’s a dead pedal. If both are dancing about like a bairn on Lucozade, you've got a wiring or earthing issue. Also, check your floor mats! I’ve had customers swear the car is broken when a thick rubber mat was just jamming the pedal travel and confusing the ECU.
Can you drive with P2138?
Limp mode.
Urgency: high.