This is a generic powertrain code, which means it covers all makes/models, 1996-newer. However, specific troubleshooting steps will vary depending on the vehicle.

The code P2096, post catalyst fuel trim system too lean on bank 1 simply translates to a lean (too much air and not enough fuel) condition the PCM recognized through the signals from the oxygen sensors. Bank 1 has no meaning on a four or straight six cylinder engine with a single exhaust. On a V-6 or V-8 engine it refers to the oxygen sensor on the number one cylinder side of the engine as bank 1.

A series of oxygen sensors in the exhaust system signal the fuel mixture ratio at all times. Each exhaust system with a catalytic converter will have two sensors — one between the engine and the converter and one after the converter.

Oxygen sensors signal the engine management computer the amount of oxygen present in the exhaust, which is used in determining and controlling the fuel ratio. The higher the oxygen content the leaner the fuel mixture, conversely the opposite is a rich mixture. It does so in a series of pulses called "cross counts." There is zirconium on the tip of the sensor that reacts to oxygen in a way that when hot, creates its own voltage. It must be around 250 degrees F to operate and will produce up to 0.8 volts.

In operation the oxygen sensor will cycle once every second and send a voltage to the computer that ranges from 0.2 rich to 0.8 for a rich mixture. The perfect mixture will average the signals around 0.45 volts. The computer’s target fuel/air ratio is 14.7:1. An oxygen sensor will not function at low temperatures such as start up — for this reason most forward sensors have a pre-heater to reduce their warm up time.

The mission of the oxygen sensors are twofold — to indicate the unburned oxygen in the exhaust and secondly, to indicate the proficiency of the catalytic converter. The engine-side sensor signals the mixture entering the converter and the rear sensor signals the mixture exiting the converter.

When the sensors and converter are operating properly, the front sensor will have a higher count than the rear sensor indicating a functioning converter. When the front and rear sensor agree, the front oxygen sensor has failed, the converter is plugged or another component is causing the oxygen sensor to give an erroneous signal.

This code may and may not be noticeable less for the check engine light. It depends on the cause, however, there isn’t anything that can fail on a vehicle without adversely effecting something else. Trace the problem to correct the code as soon as possible to avoid damage to any other components.

The symptoms of a P2096 code will vary depending on the component or system causing the disruption in the fuel trim. Not all will be present simultaneously.

The causes for this DTC may include:

To make a point as to the cause and effect on vehicles, consider this scenario. A simple air leak forward of the number one oxygen sensor will add additional air to the mixture un-metered by the computer. The oxygen sensor signals a lean mixture due to the un-metered air.

Immediately the computer enriches the mixture to prevent a lean mixture from causing damage due to detonation among other factors. The unnecessarily rich mixture begins to foul the plugs, contaminate the oil, heats up the converter and drops the fuel economy. These are only a few of the things that transpire under these circumstances.

It’s wise to go online and acquire the technical service bulletins (TSBs) associated with these codes and a description. Although all vehicles suffer from similar causes, some may have a service history of problems with a particular component associated with this code.

If you have access to an advanced diagnostic scan tool such as a Tech II or Snap-On Vantage, this will save you a lot of time. The scanner has the ability to graph and display digital information in real-time of each sensor’s performance. It will show the oxygen sensors in operation to easily recognize one that is malfunctioning.

Jeeps and some Chrysler products seem to suffer from poor electrical connectors, so inspect them thoroughly. Additionally, Jeeps have had several PCM updates on the later models. The reprogramming of the updates as well as oxygen sensor replacement for any reason is covered under the 8 year / 80,000 mile warranty. To check if the update has been completed, look next or behind the battery and there will be a serial number with the date of updating the computer. If it hasn’t been done it is free for the above period.