P2189: System Too Lean at Idle (Bank 2)
P2189 means the engine computer sees too much air or too little fuel on bank 2 at idle and low load, so it is adding extra fuel to compensate. It is not usually an emergency, but it turns on the check engine light and should be diagnosed soon because it affects emissions and idle quality.
You can drive, but get it checked soon
The reference does not list limp mode for this code, so the car usually drives, but a lean mixture can cause a rough idle and increases emissions. Have it checked soon, and stop driving if the engine runs badly or the check engine light flashes.
What it means
A V6 or V8 engine has two banks, which are the two sides of the engine. On engines with a front oxygen sensor on each bank, the computer watches how much fuel it has to add over time on each side. This adjustment is called long-term fuel trim. P2189 sets when bank 2 needs more added fuel than allowed at idle and low load, which means the mixture is running lean (too much air for the fuel). The reference lists GM thresholds such as an additive correction above 7 % on the 2005 2.8 and 3.6 V6, above 6.1 % on the 2008 3.6 LLT, and above about 5.5 % over two trips in GM's 2024 tables. Both banks share the throttle, crankcase ventilation and brake booster vacuum, so a leak there normally sets P2187 (the bank 1 version) and P2189 together. If P2189 appears alone, the cause is more likely something that only bank 2 sees.
Likely causes
- Intake gasket or runner leak on the bank 2 sidePossible
Unmetered air entering at the bank 2 side of the intake makes only that bank run lean.
- Shared vacuum leak, usually with P2187 present tooPossible
A leak at the throttle, crankcase ventilation or brake booster vacuum affects both banks and normally sets both codes.
- Bank 2 front sensor, its wiring or an injector on that bankLess likely
A faulty sensor, damaged wiring or a weak injector can make bank 2 look or run lean while bank 1 stays normal.
What you may notice
- Check engine light (malfunction indicator lamp) on
- Rough or hunting idle, meaning the idle speed rises and falls
What to check, cheapest first
- 1Read all stored codes and note whether P2187 is also present, since both codes together point to a shared leak. · you can do it
- 2Look over the intake hoses, crankcase ventilation hoses and the brake booster vacuum line for cracks, loose clamps or disconnected fittings. · you can do it
- 3Listen for a hissing sound at idle around the intake manifold and throttle body. · you can do it
- 4Compare long-term fuel trims for both banks at idle and at 2500 rpm with a scan tool to see where the extra fuel is needed. · mechanic
- 5Smoke test the intake to find leaks at the manifold gasket, runners and shared vacuum connections. · mechanic
- 6Check the bank 2 front oxygen sensor readings and wiring, and test the injectors on that bank. · mechanic
Related codes
Frequently asked questions
Can I drive with P2189?+
Usually yes for a short time, since limp mode is not listed for this code. Get it diagnosed soon, and avoid driving if the engine runs rough or the check engine light flashes.
Can a loose gas cap cause P2189?+
The reference does not list the gas cap as a cause. P2189 is about extra fuel being added on bank 2, so look at intake leaks and the bank 2 sensor, wiring and injectors first.
Will P2189 pass an emissions test?+
Probably not. The code is emissions-related and turns on the check engine light, which normally causes a failed test until the repair is done and the light stays off.
What does it mean if P2187 is also set?+
Both codes together usually mean a leak shared by both banks, such as at the throttle, crankcase ventilation or brake booster vacuum.
Written with the help of AI from the public OBDex definition (CC0). Each make may use the code differently. Updated: 2026-11-10