System to lean fuel bank 1, Service engine soon light always on

Hi,

The most common cause of a lean fuel mixture is an engine vacuum leak. In this case, it is limited to only one side of the engine. In that case, it could be fuel pressure or even an exhaust leak pre-catalytic converter.

First, here is a link that explains how to check for vacuum leaks. Try this.

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

As far as an exhaust leak, do you hear any ticking or loud exhaust from the engine?

Also, there could be an issue with a fuel injector or fuel pressure. You can actually perform a fuel injector balance test. Here are the directions for it. It does require some specialized tooling.

1996 Chevy Truck K 1500 Suburban 4WD V8-5.7L VIN R
Fuel Injector Balance Test
Vehicle Powertrain Management Computers and Control Systems Testing and Inspection Component Tests and General Diagnostics Fuel Injector Balance Test
FUEL INJECTOR BALANCE TEST
Fuel Injector Balance Test (1 Of 2)

pic 1

Fuel Injector Balance Test (2 Of 2)

pic 2

Fuel System Controls

pic 3

CIRCUIT DESCRIPTION

The Fuel injector Tester J 39021-301 and the injector switch box J 39021-210 energize the injector for a precise amount of time allowing a measured amount of fuel into the manifold. This causes a drop in fuel rail pressure that can be recorded and used to compare each injector. All injectors should have the same pressure drop 10 kPa (1.5 psi).

TEST DESCRIPTION

The numbers below refer to the step numbers on the diagnostic table.
2. This step checks for the proper fuel pressure.
3. This step checks for a decrease in the fuel pressure after energizing each injector.

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Let me know if this helps or if you have other questions.

Take care and God Bless,

Joe