Error Code P2196 is defined as O2 Sensor Signal Stuck Rich (Bank 1 Sensor 1)

This error code is a generic trouble code, meaning it applies to all vehicles equipped with the OBD-II system, especially those made since 1996 up to present. Specifications on the definition, troubleshooting, and repairs, of course, vary from one make and model to another.


Error Code P2196 means there is an excessive amount of fuel measured by Bank 1 Sensor 1. Bank 1 is the bank cylinder that contains the number 1 cylinder. Sensor 1 is the sensor before the catalytic converter.

This code is set when there is too much fuel being injected into the combustion chamber, which can be caused by a variety of factors and failures.

For some vehicles like Toyotas, this code refers to A/F (Air/Fuel ratio) sensors, which are basically more sensitive versions of oxygen sensors.

Other similar codes include:

Common Symptoms

As with other error codes, this code activates the Check Engine light and registers the code to the vehicle’s memory system. Other symptoms include:

  • Black smoke coming out of the tailpipe
  • Engine misfires
  • Poor fuel mileage
  • Rough running
  • Low fuel output

Possible Causes

As said earlier, many factors lead to the excessive fuel in the combustion chamber. The most common is defective fuel pressure regulator diaphragm. Other possible causes include:

  • High fuel pressure
  • Damaged ECT (Engine Coolant Temperature) sensor
  • Damaged wiring to the ECT
  • Stuck open fuel injector

How to Check

As with other error codes, diagnosing this code requires a scan tool to monitor both the short term and long term fuel trim values and the O2 sensor or Air/Fuel ratio sensor readings. Technicians also look at the freeze frame data to see the conditions when the code was set. This will help them determine whether the O2 A/F sensor is working properly. Then, they will compare their data with the values set by the manufacturers.

Whenever there is no available scan tool, a multimeter scanner can be used to back probe the terminals on the O2 sensor wiring connector. Technicians will check for ground, short to power, open circuits, etc. Then compare the specs to the specs set by the manufacturer.

Next, they inspect the connectors and wirings that lead to the sensor. They look for loose connections, chaffed or rubbed wires, melted wires, etc. and repair as needed.

Next, they check the vacuum lines and look for leaks. Carburetor cleaner or propane can also be used to check for vacuum leaks for the hoses while the engine is running. If the RPM changes when the vacuum leak is being checked, then there’s likely a leak. This step can be tricky and dangerous, which is why technicians usually have a fire extinguisher within reach in case something goes wrong.

If it’s been determined that vacuum leak is the problem, then all vacuum lines must be replaced, especially if they’re older and getting brittle.

Next, technicians perform fuel pressure test to verify the readings and compare them with the specs set by the manufacturers.

If you have the budget and you only have an engine with more than one bank, and the problem is only with one bank, you can simply swap the sensor from one bank to the other. Then clear the code, and see if the code is followed to the other bank. This will tell you if it’s the sensor/heater itself that’s failed.

How to Fix

  • Replacement of fuel pressure regulator
  • Replacement of MAF (Mass Air Flow) sensor
  • Replacement of ECT(Engine Coolant Temperature) sensor
  • Repair damaged wiring to the ECT
  • Replacement of leaking or stuck open fuel injector or injectors
  • Replacement of O2 sensor
  • Tune up. Replace the spark plugs, plug wires, cap and rotor, coil pack or ignition wires

It is advisable to always check for outstanding TSB (technical service bulletins) for your vehicle, in cases the PCM can be recalibrated to fix this problem. Though not a common fix, there are some cases that it can be solved this way. TSBs could also call for replacement of the sensor.

When replacing O2 or AF sensors, make sure to use a high-quality sensor. In most cases non-OEM sensors are of lesser quality will not perform correctly and will cause the problem. Thus, it’s highly recommended that you stick with OEM brand replacements.