Toyota RAV4 – P0171 – system to lean bank 1

This Toyota RAV4 with 2.4l engine was prolonged starting it took extra time to start the vehicle even after 15min switched off, the check engine light was on

Scan data revealed. P0171 system to lean bank 1.

Fuel trim graph

The fuel trim graph shows the fuel system is adding so much fuel to the mixture and can’t add anymore so the ecu report a p0171 code

Our thoughts on this was to run an volumetric efficiency test to prove the air entering the engine is correct and that the ecu is controlling fuel delivery as best as it can

Volumetric efficiency test

The chart shows that the air entering through air mass meter and that calculated air mass is correct.

This can only mean there is something outside the ecu control area that’s is the issue.

Manual checking of the fuel pressure was carried out.

Fuel pressure test


The fuel supply was not what it should be pressure to fuel rail should be 350kpa. We where well short of that

Installing a new fuel pump module

And a retest of fuel pressure shows all is well and that fuel trims are back to normal