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P2191 OBD-II Trouble Code: System Too Lean at Higher Load Bank 1

Check Engine Light

P2191 code definition

System Too Lean at Higher Load Bank 1

What the P2191 code means

P2191 is an OBD-II generic code for the engine control module (ECM) detecting that the fuel control has reached its rich limits when the engine is under load on bank 1.

What causes the P2191 code?

  • The engine control module (ECM) controls the fuel using a closed loop feedback system. If the system is trying to enrich the fuel mixture and the O2 sensor keeps saying the system is too lean on bank one, or if the system reaches 25% enrichment and the O2 sensor still indicates the system is lean, then the Check Engine Light is turned on and the code P2191 is set.

  • The fuel injection system on bank one is clogged causing the lean condition.

What are the symptoms of the P2191 code?

  • The Check Engine Light will be illuminated and the code is set in the ECM’s memory as a fault.
  • The engine will run lean on bank one and the engine may run rough and misfire.
  • The engine may hesitate on acceleration.

How does a mechanic diagnose the P2191 code?

  • Scans for codes and documents the code in the ECM, then looks at the freeze frame data for failure

  • Monitors the O2 sensors for bank 1 while manually enriching the mixture with propane to see if the O2 sensor indicates rich

  • Removes all spark plugs on bank one of the engine and checks to see what plug is running lean

  • Follows the manufacturer pinpoint tests for diagnosis and replaces the clogged or defective injector for the lean running cylinder

Common mistakes when diagnosing the P2191 code

  • Clearing ECM memory codes before checking the freeze frame data for the main failure problem, so the failure may be duplicated and repaired

  • Failing to clear the ECM codes after the codes are fixed so the ECM will enable the system to be normal again

How serious is the P2191 code?

Code P2191 is a code indicating the engine is running lean on only one side, and this lean condition can cause internal engine damage or cause the engine to misfire.

What repairs can fix the P2191 code?

Additional comments for consideration regarding the P2191 code

Code P2191 is for a lean running engine on bank one and the most common problem is the injectors getting clogged over time. As they clog over time, the engine will compensate by running the injectors rich to bring the system back to normal.

Need help with a P2191 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
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