The MAF sensor signal is within range but doesn't match expected values.
P0101 — also written PO1O1, P 0101, 0101 — is the OBD-II code for mass air flow range/performance. Same code, same fix: this page covers every spelling of it.
Mass Airflow (MAF) Sensor Range/Performance — the ECU is telling you the airflow value it's reading from the MAF sensor doesn't correlate with the engine load it expects (RPM, throttle position, MAP). On UK cars this is the #1 airflow-related code we clear in the workshop, and 6 out of 10 times it's a dirty MAF hot-wire that a £5 can of MAF cleaner brings back to life — NOT a failed sensor. Most-affected are Nissan Qashqai / Juke 1.5 dCi, VW/Audi 2.0 TDI, Ford EcoBoost, and Peugeot / Citroën 1.6 HDi.
P0101 is a sensors fault code, typically costing £20–£300 to put right in a UK garage.
What P0101 actually feels like to drive
- Hesitation and flat-spot from 1,500–2,500 RPM, worst under gentle acceleration
- Slight power loss and 2–5 mpg drop over the last 5,000 miles
- Slow to respond to throttle, especially warm
- Occasional cold-start stall or lumpy idle for the first 20 seconds
- Black smoke on hard acceleration from diesels (MAF under-reading, ECU over-fuelling)
- Limp mode above 3,500 RPM that clears on key cycle then returns
- Paired codes: P0102 (MAF low), P0103 (MAF high), P0299 (turbo underboost via MAF drift), P0401 (EGR flow miscalculation from MAF)
What causes P0101?
- Dirty MAF sensor
- Air leak after MAF
- Blocked air filter
- Failed MAF
UK vehicles that throw P0101 most often
- Nissan Qashqai / Juke / X-Trail 1.5 dCi & 1.6 dCi (K9K / R9M) — MAF failure epidemic
- VW Golf / Passat / Audi A3 / A4 / Skoda Octavia 2.0 TDI CR — MAF drift, contaminated by EGR soot
- Ford Fiesta / Focus / Kuga 1.0 & 1.6 EcoBoost — MAF plus split intake boot
- Peugeot 208 / 308 / 3008 1.6 HDi / 1.2 PureTech — MAF cleaning or replacement
- Vauxhall Astra / Corsa 1.4 Turbo (A14NET) — cracked intake manifold reads as MAF fault
- BMW 320d / 520d N47 / B47 — MAF plus swirl flap issues
- Fiat 500 / Panda / Punto 1.3 MultiJet — MAF sensor
- Mini Cooper / Cooper D — MAF drift with age
How P0101 is fixed
- MAF cleaner spray
- Replace air filter
- Check intake boots
- Replace MAF
The P0101 misdiagnosis that wastes money
P0101 is the classic 'garage fits a £180 MAF sensor and the code comes back' code. Bob's 32 years on the tools rule: before spending anything on a new MAF, three things need doing. One — clean the existing MAF properly. Not with brake cleaner (kills the hot-wire), not with WD-40 (leaves residue), not with a rag (breaks the wire). Only with a proper CRC MAF sensor cleaner or Wurth MAF cleaner — three long sprays down each side of the hot-wire, air-dry 10 minutes, refit. On around 60% of P0101s we see, that alone clears the code for another 30,000+ miles. £5 job. Two — inspect the entire intake tract between the MAF and the turbo/throttle body for a split intake boot or a loose jubilee clip. Unmetered air entering AFTER the MAF makes the engine ingest more air than the MAF reports, and the ECU stores P0101 blaming the sensor. Common split points: Ford EcoBoost degas hose, Nissan Qashqai 1.5 dCi rubber concertina boot, VW 2.0 TDI intake pipe joint at the turbo. Three — check for EGR soot contamination on diesels. On any 2.0 TDI CR / 1.6 HDi / 1.5 dCi with P0101, the MAF hot-wire gets coated by recirculated EGR carbon and reads 15–25% low. Clean the EGR at the same time or the P0101 returns within 2,000 miles. Nissan 1.5 dCi is the one exception — genuine MAF failure is common enough on these that if cleaning doesn't clear it, a Bosch replacement (never eBay-cheap unbranded) is the right call.
What a UK garage should charge for P0101
Diagnostic + live-data MAF plausibility check £45–£70. MAF sensor professional clean £20–£45 (this fixes the majority). Genuine Bosch / Denso / Hitachi MAF replacement £90–£220 fitted — Nissan Qashqai / Juke 1.5 dCi Bosch MAF around £120–£180 fitted. Cracked intake boot / split turbo hose £35–£120 fitted. Full 'EGR + MAF service' on diesel (EGR clean + MAF clean + air filter + freeze-frame check) £140–£280.
P0101 repair cost in the UK
Most P0101 repairs land between £20–£300 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 P0101
Bob's real workshop rule on P0101: NEVER fit a MAF as the first move. Cleaning first is a five-minute job that saves the customer between £90 and £220 in 6 out of 10 cases. The one exception is Nissan Qashqai / Juke 1.5 dCi and 1.6 dCi — those MAFs genuinely fail, and if a proper clean doesn't clear P0101 within 100 miles of driving, fit a Bosch (never budget eBay units — they read wrong from day one and re-store the code inside 500 miles). On any Ford EcoBoost with P0101, always check the degas hose (small crankcase breather to the intake) for a split at the crimp — a 60p O-ring or a £25 hose kit clears the code. On any VW / Audi / Skoda 2.0 TDI CR with P0101, the code is a symptom of a bigger EGR carbon problem — clean the EGR properly at the same time or the P0101 is back within 2,000 miles. And on any BMW N47 / B47 diesel with P0101, do NOT ignore paired codes for swirl flaps — flap fragments in the intake damage the MAF and turbo simultaneously, and 'just cleaning the MAF' on one of these ends up as a £1,400 turbo job three months later.
Can you drive with P0101?
Drivable.
Urgency: medium.