P0174 on Audi: Causes, Symptoms and Fix Cost
Quick Answer
Safe to drive (short-term)
P0174 on a Audi means the engine is running too lean on Bank 2, the cylinder bank that does not contain cylinder 1. It appears on V6, V8 and boxer engines, and on inline-six engines whose engine management splits the cylinders into two banks with an upstream oxygen sensor each, such as BMW's M54, N52 and N54. 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. The cheapest fixes, a MAF clean or a split vacuum hose, can cost under 100 euros; a gasket or PCV repair runs roughly 40 to 260 euros.
- Severity
- Moderate · Fuel System
- Typical repair cost, all makes
- €30-€700
Connect a standard OBD2 adapter (Bluetooth LE on iPhone) to your Audi and Skanyx tells you what P0174 means on that engine, whether it is safe to keep driving, and what the fix should cost. Free on iPhone and Android.
Get Skanyx freeWhat does P0174 mean on a Audi?
The Quick Answer above is the generic definition. What follows is the model-specific detail for the Audi models that log P0174.
Audi A4
2005-2024
Four-cylinder TFSI A4 models are single-bank and set P0171; P0174 shows up on the V6 cars such as the 3.2 FSI. On these the PCV/crankcase breather system is a known lean source, and the intake manifold seals on the Bank 2 side can 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 patterns noted for Audi models:
PCV/crankcase breather diaphragm failure on the V6 causing an unmetered vacuum leak
: Audi A4
Bank 2 intake manifold seal and vacuum hose cracking with age
: Audi A4
How to diagnose P0174 on a Audi with OBD2
- 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 sustained above about +10 percent shows the bank is correcting for a lean mixture, and the code typically sets near the ECU's limit of around +25 percent; 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.
| Repair | Parts Cost | Labor Cost | Total Estimate | DIY Difficulty |
|---|---|---|---|---|
| Fix vacuum leak (replace hose or gasket) | €5–€60 | €60–€200 | €65–€260 | Moderate |
| Clean or replace MAF sensor | €10–€200 | €20–€60 | €30–€260 | Easy |
| Replace PCV valve | €10–€80 | €30–€120 | €40–€200 | Easy |
| Replace fuel pump | €100–€400 | €100–€300 | €200–€700 | Professional |
| Clean fuel injectors | €15–€50 | €50–€150 | €65–€200 | Moderate |
Prices estimated as of October 2026. Costs vary by region, vehicle, and shop.
Codes related to P0174
These codes are often seen alongside P0174 or point to related issues, on any make:
Looking for the full P0174 reference (all makes, full diagnosis flow, complete repair cost matrix)? See the main P0174 guide