01 Why Does My Car Go Faster Than the Speed Limit? • 02 People Cannot Believe The Secret Function Of The Small Arro… • 03 The Common Mistake Nearly Half of Drivers Are Making Withou… • 04 The Business of Car Importation: Profits and Risks Explained • 05 This Is How to Fix a Car That Won’t Start After Replacing t… • 06 Does Your Car Hesitate When Accelerating? Here's What The P… • 07 Adapting to Autonomous Transmissions: How Self-Shifting Car… • 08 Valve Adjustment: The Essential Tune-up for a Healthy and H… • 09 Symptoms of a Bad Oxygen Sensor • 10 Is Your Car Blowing Hot Air? Signs of a Failing Air Conditi… •

DTC codes / BMW codes / P1164

P1164 · BMWFuel Trim Adaptation Additive Per Ignition Bank 2 Low

P1164 on BMW vehicles indicates that the engine control module has detected an excessively low additive fuel trim adaptation value for bank 2 during ignition-on or idle conditions, meaning the computer is adding maximum fuel to compensate for a lean condition that it cannot correct within normal limits. The additive adaptation specifically affects low-load, low-rpm operation, so the fault points to a vacuum leak or fuel delivery issue that is most pronounced at idle.

SystemPowertrain
Code typeBMW specific
SeverityMedium
Fix difficultyProfessional
AreaFuel and air metering

Symptoms you may notice

  • Illuminated check engine light, often with no other noticeable symptoms
  • Rough or unstable idle, especially when the engine is cold
  • Occasional hesitation or stumble when accelerating from a stop
  • Slightly elevated fuel consumption as the engine control module adds extra fuel
  • In severe cases, a lean misfire code or reduced engine power may accompany the warning light

Common causes, most likely first

  1. Vacuum leak on bank 2, such as a cracked intake boot, deteriorated vacuum hose, or leaking intake manifold gasket
  2. Faulty or contaminated mass air flow sensor reporting less air than actually enters the engine
  3. Leaking or stuck-open fuel injector on bank 2 causing an imbalance that the oxygen sensor interprets as lean
  4. Weak fuel pump or restricted fuel filter reducing fuel delivery at low demand
  5. Failed oxygen sensor on bank 2 providing a false lean signal to the engine control module
  6. Crankcase ventilation system leak, including a torn valve cover diaphragm or failed PCV valve
  7. Intake manifold runner control fault or sticking swirl flap causing uneven air distribution to bank 2

How to diagnose and fix it

  1. Connect a scan tool and read live fuel trim data for both banks to confirm bank 2 additive trim is pegged high while bank 1 remains normal
  2. Perform a visual inspection of all intake and vacuum lines on bank 2, including the intake boot, valve cover breather hoses, and intake manifold gaskets
  3. Smoke test the intake system to pinpoint any vacuum leaks that are not visible to the eye
  4. Clean or replace the mass air flow sensor if its reported airflow does not match expected values at idle
  5. Check fuel pressure and delivery volume at the rail to rule out a weak pump or restricted filter
  6. Swap the bank 2 oxygen sensor with the bank 1 sensor to see if the lean trim follows the sensor, confirming a sensor fault
  7. If all external causes are ruled out, perform an injector balance test or remove injectors for professional cleaning and flow testing

Why bank 2 additive trim runs lean

  • Additive fuel trim only affects idle and very low load, so a vacuum leak that seals itself as the engine moves under load can set P1164 without ever triggering a lean code at cruise.
  • A failing crankcase ventilation diaphragm on BMW inline-six engines often leaks unmetered air into bank 2 specifically, and the leak is hidden inside the valve cover so a visual inspection misses it.
  • Technicians sometimes replace the bank 2 oxygen sensor first because the code names bank 2, but a sensor that reads lean when the mixture is actually correct will also set this code and is easily misdiagnosed.
  • The additive adaptation value is stored per ignition cycle, so the code may only set after several cold starts and short idle periods, which makes intermittent vacuum leaks hard to reproduce in a quick shop visit.
  • A dirty or failing mass air flow sensor on BMW engines often under-reports airflow at idle, causing the engine control module to add fuel and push additive trim beyond its limit on both banks, but bank 2 may hit the threshold first.

Can I keep driving with P1164?

You can usually drive the vehicle short distances to a repair shop, but avoid prolonged idling and heavy acceleration because a persistent lean condition can overheat the catalytic converter and cause misfires. If the check engine light begins flashing or the engine runs rough, stop driving and arrange a tow.

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.

Running on fumes Free guides aren't free to make. Top up the tank. Any amount, one time. Fuel the Garage