The P2189 code on your 2023 Acura MDX indicates the fuel system is running too lean at idle on bank 2. This code affects your MDX's 3.5L V6 or available Type S 3.0L turbo V6 engine, signaling excessive lean condition on the rear cylinder bank at idle speeds.
Understanding P2189 on Acura MDX
Code P2189 is the bank 2 counterpart to P2187. It indicates the ECM is making maximum positive fuel trim corrections at idle for bank 2 but still cannot achieve proper air-fuel ratios. This typically indicates unmetered air is entering the engine on the bank 2 side.
Common Symptoms
- Check engine light on
- Rough idle, especially when cold
- Idle speed variations
- Possible lean misfire at idle
- Engine may run fine at higher speeds
- May feel slight vibration at idle
Primary Causes
- Vacuum leak affecting bank 2
- Intake manifold gasket leak on bank 2 side
- Bank 2 injector O-ring leak
- Cracked vacuum hose on bank 2
- EGR system leak affecting bank 2
- Bank 2 oxygen sensor reading incorrectly rich
- Brake booster vacuum leak
Diagnostic Procedure for 2023 Acura MDX
Monitor bank 2 fuel trim at idle - high positive values confirm lean condition. Compare to bank 1 trims; large difference indicates bank-specific leak. Perform smoke test focusing on bank 2 intake runners, injector O-rings, and gasket area. Check vacuum hoses routed to bank 2 components. Swap O2 sensors between banks to verify sensor isn't causing false readings.
Repair Solutions
Repair vacuum leaks found during smoke testing. Replace leaking intake manifold gasket. Replace damaged vacuum hoses. If injector O-rings are leaking air, replace them during fuel injector service. Address any EGR system leaks. Replace faulty oxygen sensor if swap test confirms sensor issue. Clear codes and verify normal fuel trims at idle after repair.