What Causes the "P0172 - Fuel Trim Too Rich (bank 1)" Code in a 2001 Honda CR-V?

The most common cause for a P0172 code on a 2001 Honda CR-V is a faulty mass air flow sensor. Begin diagnosis with the power control module.

Fault code P0172 indicates that the computer in a 2001 Honda CR-V is no longer able to properly adjust the mixture between fuel and air. The term "too rich” means that the computer is subtracting too much fuel from the fuel/air mixture. The fault occurring on bank 1 indicates that the problem is located on the side of the engine that has the #1 cylinder.

The mass air flow sensor monitors the amount of air entering the fuel line. Air changes in density as it expands and contracts with temperature and pressure changes, and the mass air flow sensor monitors those changes, ensuring that the proper air/fuel mixture is maintained. When the mass air flow sensor becomes faulty, it delivers incorrect information to the power control module. Based upon this incorrect information, the power control module compensates for the difference, which triggers the P-0172 code.

While the most common cause for the P-0172 code is the mass air flow sensor, the power control module should be closely examined on a 2001 Honda CR-V. Modern automobiles rely on a computer that must be updated with the latest software to function properly. Outdated fuel map software will often inaccurately compensate for engine wear, causing the air/fuel mixture to grow rich, triggering the P-0172 code.

Other possible causes for a P-0172 code include a defective manifold absolute pressure sensor, engine mechanical problems, ignition misfires, a defective fuel pressure regulator or a defective or restricted fuel return line.