The upstream oxygen sensor heater circuit has failed.
P0030 — also written POO3O, P 0030, 0030 — is the OBD-II code for ho2s heater control circuit (bank 1 sensor 1). Same code, same fix: this page covers every spelling of it.
O2 sensor heater control circuit — Bank 1 Sensor 1 (upstream lambda). This is the heater element inside the pre-cat sensor, not the sensor's air/fuel signal (that's P0130). The heater warms the ceramic element so it reaches operating temperature within 30 seconds of a cold start; without it the ECU runs open-loop rich and stores a code. On UK cars P0030 is a failed heater element four times out of five, but a blown 15A ECU-relay fuse looks identical on the scan tool and costs 50p to fix — always check the fuse before condemning the sensor.
P0030 is a sensors fault code, typically costing £80–£350 to put right in a UK garage.
What P0030 actually feels like to drive
- Engine warning light comes on within 1–3 miles of a cold start every time
- MPG drops 3–6 in short-trip city driving (ECU can't close-loop until the sensor's warm)
- MOT emissions test failure on CO or HC when the tester samples cold
- Sooty smell from the exhaust on start-up, especially on frosty mornings
- No drivability issue — car pulls normally, no misfire, no limp
- Sometimes clears itself after a 30-minute motorway run then returns overnight
- Often paired with P0031 (heater low) or P0032 (heater high) — same sensor circuit
What causes P0030?
- Failed O2 sensor heater
- Blown fuse
- Wiring damage
UK vehicles that throw P0030 most often
- Vauxhall Astra H / J / Corsa D / E 1.2 / 1.4 / 1.6 petrol — Bosch LSU4 heater failure at 70–100k
- Ford Fiesta / Focus / EcoSport 1.0 EcoBoost — heater element burns out early on stop-start cars
- VW Polo / Golf / Skoda Fabia 1.2 / 1.4 / 1.6 petrol — genuine sensor failure
- Toyota Yaris / Auris / Prius hybrid — sensor internal failure past 100k
- Honda Jazz / Civic / CR-V — plug corrosion from wet-belly road salt
- Mini Cooper / One (R56 / F55 / F56) — sensor plug seal fails, water ingress
- Nissan Qashqai / Micra 1.2 / 1.5 petrol — heater failure
- Suzuki Swift / Vitara 1.2 / 1.4 — genuine sensor wear
How P0030 is fixed
- Replace O2 sensor
- Check fuse and wiring
The P0030 misdiagnosis that wastes money
Bob's 32 years on the tools rule for P0030: BEFORE spending £180 on a new lambda, spend two minutes on the fuse box. On Vauxhall Corsa D / Astra H the O2 heater feed shares a fuse with the fuel-injection relay in the under-bonnet box — a blown fuse stores P0030 identically to a failed sensor. Same on Ford 1.0 EcoBoost (fuse F27 or F42 depending on year). A 50p fuse fixes 15% of these cars outright. Second most common miss: the plug on the sensor. On any car older than 8 years, unclip the connector at the sensor and inspect for green corrosion, water inside the shell, or a burnt pin — clean and re-terminate with dielectric grease before condemning the sensor. Third miss: fitting a cheap unbranded eBay lambda. Every P0030 sensor MUST be a genuine Bosch, Denso, NGK or NTK to match the OE heater resistance (usually 8–14Ω cold). A £22 eBay 'universal 4-wire' has the wrong heater spec and re-stores the code inside a fortnight. Fourth: never assume P0030 alone. Always check for P0031 (heater circuit low — usually shorted wiring to ground) and P0032 (heater circuit high — usually open circuit). The trio together points to loom damage or a burnt ECU driver, not the sensor.
What a UK garage should charge for P0030
UK independent garage: diagnostic + fuse check + heater-circuit resistance test £30–£60 (this is the appointment that saves the money). Fuse replacement 50p to £5, five minutes. Sensor plug clean + dielectric grease £20–£45. Upstream (pre-cat) O2 sensor: Genuine or Bosch/NGK/Denso/NTK £75–£180 fitted for most UK petrols, £180–£320 fitted on premium German cars where the sensor is buried under a heat shield. Wiring repair (splice, heat-shrink, re-loom away from exhaust heat) £45–£120. Full pair (upstream + downstream) £160–£360 fitted — sensible if the car is over 100k because they typically fail within 20k of each other. On a Toyota / Honda hybrid, insist on the OE part number for the correct ceramic warm-up time. Main dealer: 40–60% more.
P0030 repair cost in the UK
Most P0030 repairs land between £80–£350 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 P0030
Bob's real workshop shortcut for P0030 in 5 minutes: multimeter across pins 3 and 4 of the disconnected sensor plug (the two white or grey wires — heater circuit). Cold reading should be 8–14Ω (varies by manufacturer — check the workshop spec, but always finite). Open circuit (OL / infinity) confirms a burnt heater element inside the sensor — replacement is the only fix. Reading within spec means the sensor is fine and the fault is upstream: check the fuse, check the plug for corrosion, check the wire from the sensor back to the ECU for chafing where it crosses the exhaust manifold. On a Ford 1.0 EcoBoost, if P0030 arrives alongside coolant loss you have a much bigger problem than a lambda — stop driving and get it compression-tested. On any hybrid (Toyota, Honda, Lexus) the pre-cat lambda works overtime because the engine cycles on and off constantly, and the OE spec matters more than on a conventional car — never fit anything other than the exact part number listed on the sticker. If a garage quotes you £180 for a lambda without checking the fuse or the plug first, walk away. Not sure whether yours is a £5 fuse or a £160 sensor? <a href="/ask-a-mechanic-uk?code=P0030">Ask Bob about your P0030</a> for £14.99 with the make, model, mileage and any paired codes — you'll get a straight answer before you spend the money.
Can you drive with P0030?
Yes, but emissions and MPG will suffer.
Urgency: low.