Vacuum leak from a cracked or disconnected intake boot, hose, or intake manifold gasket on bank 2; Faulty pre-catalyst oxygen sensor on bank 2 giving a false lean reading; Leaking fuel injector seals or a clogged injector on bank 2; Low fuel pressure from a weak fuel pump or restricted fuel filter; Mass air flow sensor contamination or failure causing an incorrect air measurement; PCV valve or crankcase ventilation hose leak on bank 2; Exhaust leak before the oxygen sensor on bank 2 allowing outside air into the exhaust

DTC codes / BMW codes / P1092

P1092 · BMWPre-Catalyst Fuel Trim Too Lean Bank 2

Q: What does code P1092 mean?

Pre-Catalyst Fuel Trim Too Lean Bank 2. P1092 on BMW vehicles means the engine computer has detected a lean fuel mixture on bank 2 before the catalytic converter, based on oxygen sensor feedback. The computer has added fuel to compensate, but the long-term fuel trim has exceeded the lean limit, indicating unmetered air or insufficient fuel reaching the cylinders on that bank.

P1092 on BMW vehicles means the engine computer has detected a lean fuel mixture on bank 2 before the catalytic converter, based on oxygen sensor feedback. The computer has added fuel to compensate, but the long-term fuel trim has exceeded the lean limit, indicating unmetered air or insufficient fuel reaching the cylinders on that bank.

SystemPowertrain

Code typeBMW specific

SeverityMedium

Fix difficultyIntermediate

AreaFuel and air metering and auxiliary emission controls

Symptoms you may notice

Often no symptoms besides the warning light, especially in early stages
Rough idle or misfire that may be more noticeable when cold
Hesitation or stumble during acceleration
Reduced engine power or limp mode in severe cases
Poor fuel economy despite the lean condition
Occasional backfire or popping from the exhaust

Common causes, most likely first

Vacuum leak from a cracked or disconnected intake boot, hose, or intake manifold gasket on bank 2
Faulty pre-catalyst oxygen sensor on bank 2 giving a false lean reading
Leaking fuel injector seals or a clogged injector on bank 2
Low fuel pressure from a weak fuel pump or restricted fuel filter
Mass air flow sensor contamination or failure causing an incorrect air measurement
PCV valve or crankcase ventilation hose leak on bank 2
Exhaust leak before the oxygen sensor on bank 2 allowing outside air into the exhaust

How to diagnose and fix it

Inspect all intake hoses, boots, and vacuum lines on bank 2 for cracks or loose connections
Check fuel pressure with a gauge and compare to BMW specifications
Perform a smoke test on the intake system to locate hidden vacuum leaks
Examine the pre-catalyst oxygen sensor on bank 2 for contamination or damage and test its signal with a scan tool
Clean or replace the mass air flow sensor if contaminated
Test fuel injectors for flow and spray pattern, and replace faulty seals or injectors
Check for exhaust leaks before the oxygen sensor on bank 2 and repair as needed

Before you replace the bank 2 oxygen sensor

A lean code on only one bank often points to a vacuum leak specific to that bank, such as a cracked intake manifold gasket or a disconnected PCV hose, rather than a global fuel delivery issue.
The pre-catalyst oxygen sensor can be misled by an exhaust leak before it, which draws in outside air and creates a false lean signal that mimics a genuine lean condition.
BMW engines are prone to crankcase ventilation valve failures that cause unmetered air to enter the intake, triggering lean codes on one or both banks.
Fuel trim readings should be monitored live; if bank 2 long-term fuel trim is maxed out positive while bank 1 is normal, the fault is almost certainly bank-specific.
A contaminated mass air flow sensor can skew fuel trim across both banks, but sometimes the adaptation affects one bank more due to intake design, so do not overlook it.

Can I keep driving with P1092?

You can drive cautiously to a repair shop, but avoid heavy acceleration or sustained high speeds because a lean condition can cause overheating and catalytic converter damage. If the engine is misfiring or overheating, stop driving and have it towed.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for BMW vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.