
P1090 (Volkswagen, Audi, Skoda, Seat) Exhaust gas bank 2 – mixture adaptation range 2, mixture too lean
Content
P1090 - OBD-II Trouble Code Technical Description
Fault code P1090 indicates that the mixture is too lean in the mixture adaptation range 2 (exhaust bank 2) in Volkswagen, Audi, Skoda, Seat vehicles.
What does the fault code mean P1090?
Trouble code P1090 indicates a problem with the fuel-air mixture in exhaust bank 2, namely in mixture adaptation zone 2, in Volkswagen, Audi, Skoda, Seat vehicles. This means that the mixture control has not reached the lower lean limit, indicating insufficient combustion, an intake manifold leak, or faulty sensors.

Possible reasons
Possible causes of DTC P1090:
- Defective oxygen sensor: The oxygen sensor measures the oxygen content of the exhaust gases and helps control the fuel-air mixture. If the sensor is faulty, it may send incorrect data to the engine control module, resulting in a P1090 code.
- Intake air leaks: Intake air leaks can result in an incorrect air/fuel mixture ratio, which can cause P1090.
- Fuel injection system malfunctions: Faulty fuel injectors or problems with fuel pressure regulation can cause improper fuel distribution in the engine cylinders, causing P1090.
- Problems with the engine control module (ECU): If the engine control module is not working properly or has errors in the software, this can also cause the P1090 code.
- Incorrect signals from other sensors: Problems with other sensors, such as the coolant temperature sensor or air pressure sensor, can cause the engine management system to malfunction and cause P1090.
What are the symptoms of a fault code? P1090?
Symptoms for DTC P1090 may include the following:
- Loss of engine power: If the fuel/air mixture is not rich enough (lean mixture), it may cause the engine to lose power when accelerating or idling.
- Unstable idle: Incorrect fuel/air mixture ratio can result in rough idle or even no idle.
- Increased fuel consumption: A lean mixture can result in increased fuel consumption as the engine may consume more fuel to maintain normal operation due to insufficient combustion.
- Increased emissions of harmful substances: Incorrect combustion of the mixture can lead to increased emissions of harmful substances such as nitrogen oxides and hydrocarbons.
- Unstable engine operation during cold start: During a cold start, the engine may run unsteadily due to an insufficiently rich mixture of fuel and air.
These symptoms can manifest differently depending on the specific vehicle and its condition, so it is important to contact a professional to diagnose and fix the problem.
How to diagnose a fault code P1090?
The following steps are recommended to diagnose DTC P1090:
- Scanning trouble codes: Use the OBD-II diagnostic scanner to determine all fault codes in the engine control module.
- Oxygen sensor test: Check the operation of the oxygen sensor (lambda probe) for the presence of signals and its response to changes in the fuel and air mixture. If necessary, the sensor may need to be replaced.
- Checking for Intake Air Leaks: Check the intake manifold and connections for air leaks that could cause the mixture ratio to be incorrect.
- Checking the fuel injection system: Check the operation of the fuel injectors for even distribution of fuel in the cylinders and correct fuel pressure. Faulty injectors can cause the mixture to become lean.
- Engine Control Module (ECU) Diagnostics: Check the operation of the engine control module for errors and the correctness of its software. If necessary, reprogram or replace the ECU.
- Checking other sensors and pressure sensors: Check the operation of other sensors, such as the coolant temperature sensor and air pressure sensor, which may affect the operation of the engine management system.
- Visual inspection and wiring check: Carefully inspect the wiring and connectors associated with the fuel injection system and sensors for damage or corrosion.
After completing these steps, you can determine the cause of the P1090 code and begin making the necessary repairs or replacing parts. If you do not have experience in diagnosing and repairing vehicles, it is recommended that you contact a qualified auto mechanic or service center.
Diagnostic errors
When diagnosing DTC P1090, the following errors may occur:
- Misinterpretation of data: Incorrect interpretation of data from sensors or scanner may lead to incorrect determination of the cause of the error.
- Faulty Components: Malfunctions of the oxygen sensor, fuel injectors or other engine management system components may cause misdiagnosis.
- Missed leaks: Failure to detect intake air leaks or other fuel leaks may result in incorrect diagnosis.
- Wiring problems: Damaged or broken wires can cause sensors to be misread and cause misdiagnosis.
- Problems in the control module: If the problem is due to a faulty engine control module (ECU), this may be missed during diagnosis.
- Lack of specialized equipment: Some problems, such as ECU software or reprogramming problems, may require specialized equipment that private car enthusiasts may not have.
It is important to contact an experienced technician or service center for diagnosis and repair, especially if you are unsure of your skills or experience working on vehicles.
How serious is the fault code? P1090?
Trouble code P1090 can be more severe or less severe depending on the specific circumstances and why it occurs. In general, an incorrect fuel/air mixture ratio can lead to a number of problems that affect engine performance and a vehicle's environmental performance; several factors that can influence the severity of the P1090 code are:
- Loss of power and efficiency: Incorrect combustion of the mixture may result in loss of engine power and poor engine efficiency, which may adversely affect vehicle performance.
- Increased fuel consumption: If the fuel/air mixture is not rich enough, it may result in increased fuel consumption, which in turn will negatively affect the vehicle's economic efficiency.
- Emissions of harmful substances: Incorrect combustion of the mixture can lead to increased emissions of harmful substances such as nitrogen oxides and hydrocarbons, which can negatively affect the vehicle's environmental performance and lead to violation of environmental safety standards.
Overall, although the P1090 code itself does not indicate a catastrophic failure, its presence requires careful attention and timely repair to prevent more serious engine and vehicle performance problems.
What repair will help eliminate the code? P1090?
Resolving the P1090 trouble code may require several steps depending on what caused it, some possible steps to resolve this issue are:
- Replacing the oxygen sensor (lambda probe): If the oxygen sensor is faulty or fails, it must be replaced. The oxygen sensor plays a key role in regulating the fuel/air mixture, and its proper operation is essential for optimal engine performance.
- Checking and eliminating intake air leaks: Check the intake manifold and connections for air leaks as they may cause an incorrect fuel/air mixture ratio. Leaks should be repaired and new seals or gaskets installed if necessary.
- Checking and replacing fuel injectors: Check the condition and functionality of the fuel injectors. If the injectors are faulty or do not function properly, they should be replaced.
- Diagnostics and reprogramming of the engine control module (ECU): If the problem is with the ECU or engine control module software, it may need to be diagnosed and, if necessary, reprogrammed or replaced.
- Checking and replacing other engine management system components: Check the condition and functionality of other engine management system components such as coolant temperature sensors, air pressure sensors and others. If necessary, they should be replaced.
It is important to contact a qualified technician or service center for repair work. It is also recommended to maintain regular vehicle maintenance and regularly check the operation of the engine management system to prevent similar errors from occurring in the future.

