The Quick Answer above is the generic definition. What follows is what is documented for the Audi models that log P0174, checked against manufacturer data and owner reports.
DTC/P0174·Audi
P0174 on Audi: Causes, Symptoms and Fix Cost
Quick Answer
Moderate SeveritySafe to drive (short-term)Audi
P0174 on a Audi means the engine is running too lean on Bank 2, the cylinder bank that does not contain cylinder 1, so this code only appears on V6, V8, and boxer engines. The computer added the maximum extra fuel it can (long-term fuel trim past roughly +25 percent) but still measured too much air against the ideal 14.7:1 ratio. The most common cause is an unmetered air leak: a cracked vacuum hose or leaking gasket. Most repairs cost under 100 euros.
Repair cost on Audi€30 - €700
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Audi A4
2005-2024Four-cylinder TFSI A4 models are single-bank and set P0171; P0174 shows up on the V6 cars such as the 3.0 and 3.2 FSI. On these the PCV/crankcase breather system is a notorious lean source, and the Bank 2 side of the intake manifold and its gaskets crack with age and heat. Carbon build-up on direct-injection valves can worsen the lean reading.
What causes P0174 on a Audi?
Beyond the generic causes listed on the main P0174 page, these are the documented Audi-specific patterns:
Audi A4PCV/crankcase breather diaphragm failure on the 3.0/3.2 V6 causing a metered vacuum leak
Audi A4Bank 2 intake manifold seal and vacuum hose cracking with age
How to diagnose P0174 on a Audi with OBD2
Follow these steps to pinpoint the root cause of P0174:
- Check whether P0171 is also stored. Both codes together points to a whole-engine cause (dirty MAF, low fuel pressure, or a large central vacuum leak), not a Bank 2-specific fault, so start there
- Read short-term and long-term fuel trims on Bank 2 with a scan tool. A long-term trim above roughly +15 percent confirms the bank is running lean; trims that worsen at idle suggest a vacuum leak, trims that worsen under load suggest a fuel-delivery problem
- Smoke-test the intake, or spray a small amount of carburettor cleaner around the Bank 2 intake manifold gaskets, vacuum hoses, and PCV connections, watching for an RPM change that pinpoints the leak
- Inspect and clean the MAF sensor with dedicated MAF cleaner, then recheck trims; a clogged sensor element is a frequent and cheap fix
- Check fuel pressure at the rail with a gauge and compare against the manufacturer specification, both at idle and under a snap-throttle load
- Inspect for an exhaust leak ahead of the Bank 2 upstream O2 sensor and verify the sensor is switching correctly before condemning any parts
- Compare Bank 1 and Bank 2 trims side by side - a large gap between the two banks isolates the problem to Bank 2 hardware rather than a shared cause
How much does P0174 cost to fix on a Audi? (EUR)
Estimated repair costs for P0174 in EUR, compiled across makes. Expect Audi parts and labour towards the upper end of each range.
Prices estimated as of March 2026. Costs vary by region, vehicle, and shop.
Related codes that often appear with P0174 on Audi
These codes commonly cluster with P0174 on Audi vehicles:
Looking for the full P0174 reference (all makes, full diagnosis flow, complete repair cost matrix)?
See the main P0174 guideSkanyx · Audi
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