Nissan P0171

System lean on Nissan — Qashqai/Juke 1.6 HR16 and 1.2 DIG-T MAF and intake leaks.

Nissan P0171 — System lean on Nissan — Qashqai/Juke 1.6 HR16 and 1.2 DIG-T MAF and intake leaks. Typical UK independent garage cost: £25–£450.

What actually causes P0171 on a Nissan

Nissan HR16 P0171 is usually MAF contamination after 60k — these MAFs are unusually sensitive to oil mist from worn PCV systems. On HR12 DIG-T turbo, intake hose splits and PCV diaphragm failures dominate. The HR12 is a complicated little engine and P0171 with limp mode usually means a meaningful leak, not just a dirty MAF.

Nissan engines that log P0171

• HR16DE 1.6 (Qashqai/Juke)
• HR12DDT 1.2 DIG-T (Juke/Pulsar)
• MR20DE 2.0

How we diagnose P0171 on a Nissan

1. Log MAF and fuel trims with Nissan Consult or Autel
2. Smoke-test full intake from MAF to inlet manifold
3. Inspect HR12 charge pipes and PCV for splits
4. Clean MAF and re-test
5. Check intake manifold gasket integrity on HR16 over 100k

The common misdiagnosis to avoid

HR12 DIG-T P0171 with limp mode — smoke-test before MAF cleaning. These turbos crack intake hoses regularly.

Nissan P0171 repair cost in the UK

Expect £25–£450 including parts and labour at an independent garage. Main-dealer quotes on Nissan are usually higher for the same job, and the spread exists because the cheap cause and the expensive cause throw the same code — pay for the diagnosis before you pay for parts.

Bob's workshop tip

Worn PCV on HR16 oil-mists the MAF and you'll be cleaning it every 6 months — fix the PCV root cause and the MAF stays clean.

Codes usually seen alongside P0171 on Nissan

• P0174
• P0507
• P0300

Symptoms drivers report with P0171

• Hesitation or 'flat spot' pulling away from junctions and roundabouts when engine is warm
• Rough or lumpy idle, worse when air-con clicks in (extra load exposes the lean condition)
• Occasional cough or backfire through the intake when accelerating hard from low RPM
• MPG dropping 3–8 mpg over the last month with no change in driving style
• Faint hissing under the bonnet at idle (vacuum leak from cracked manifold or split hose)
• Paired codes: P0174 (bank 2 lean, V6/V8 only), P0507 (idle too high), P2187 (idle lean), P0300-series misfires

Repairs that clear P0171

• Smoke-test for vacuum leaks
• Clean MAF sensor with proper cleaner
• Test fuel pressure
• Replace fuel filter
• Replace failed sensor

For the generic, all-makes explanation of this code — meaning, every known cause and UK cost bands — see our P0171 guide.

Reading P0171 on a Nissan properly

A generic reader will show P0171 and nothing else. What matters is the freeze-frame data stored with it — engine speed, load, coolant temperature and fuel trims at the moment the fault was logged — plus whether any other module on the Nissan has logged something at the same time. Codes rarely arrive alone, and the order they were stored in usually points at which one is the cause and which are the consequences.

Clearing P0171 without fixing it

Erasing the code resets the Nissan's readiness monitors as well as the light. The fault returns on the next drive cycle if the cause is still there, and in the meantime the incomplete monitors can stop the car passing an emissions check. After a genuine repair, the car is driven until the relevant monitor completes before it is handed back.

Bob's Mechanical Repairs is an independent garage in Birnam, Dunkeld, Perthshire, with 32 years of Bob's experience on the tools. If P0171 is showing on your Nissan, bring any scan results with you — we will read the live data ourselves, confirm which cause it actually is, and price the repair before any work starts.