Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
The car has a sensor that checks the air pollution coming from the engine. This sensor is not working because its wires are touching each other in a bad way.
The NOx sensor is responsible for measuring nitrogen oxide levels in the exhaust. A short circuit in its wiring can cause incorrect readings.
The P122F code indicates that there is a short circuit in the wiring of the NOx sensor's binary oxygen sensor signal circuit for Bank 1. This can lead to incorrect data being sent to the engine control module (ECM), affecting emissions control.
• Check Engine Light is on
• Poor fuel economy
• Increased emissions
• Damaged wiring or connectors
• Faulty NOx sensor
• Corrosion in the sensor connector
NOx Sensor: A sensor that measures nitrogen oxides in the exhaust gases.
Short Circuit: An electrical circuit that allows a current to travel along an unintended path.
• Use an OBD-II scanner to confirm the code
• Inspect the wiring and connectors for damage or corrosion
• Test the NOx sensor for proper function
• Repair or replace damaged wiring
• Clean or replace corroded connectors
• Replace the NOx sensor if faulty
• OBD-II scanner
• Multimeter
• Basic hand tools
$200 - $500
Moderate
• BMW 3 Series
• Volkswagen Passat
• Mercedes-Benz C-Class
• Regularly inspect and maintain exhaust system components
• Keep sensor connectors clean and dry
• Use high-quality fuel to reduce emissions
Sensor Issue
• Do not ignore the Check Engine Light
• Have the vehicle inspected by a professional
• Consider regular maintenance checks
Check with your vehicle manufacturer for emissions-related warranty coverage.
This code has been more common in diesel engines due to their higher NOx emissions.
Moderate – Driving with this issue can lead to increased emissions and potential engine performance problems.
Ignoring emissions-related issues may lead to failing emissions tests and potential fines.
• Engine at operating temperature
• Vehicle in a safe, stationary position
The NOx sensor is typically located in the exhaust system, near the catalytic converter.
Q: Can I drive with a P122F code?
A: It's not recommended to drive for long periods with this code, as it can affect emissions and engine performance.
Q: How do I reset the Check Engine Light after repairs?
A: Use an OBD-II scanner to clear the code after repairs. If the issue is fixed, the light should stay off.
High-End · Full-system diagnostics
A full-system bidirectional platform aimed at advanced DIY users and professional diagnostic workflows.
Network faults often require full-system access instead of a generic code reader alone.
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Universal · Digital multimeter
A solid entry-level multimeter for voltage, continuity, resistance, and basic electrical troubleshooting.
Helpful for checking voltage drops, grounds, and basic circuit health when modules are not communicating.
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Universal · Wire connectors and repair kit
Useful when diagnosis points toward damaged wiring, corroded terminals, or connector repairs.
Useful if diagnosis points toward damaged connectors, wiring, or terminal repairs.
View on AmazonThese are optional diagnostic tools, not guaranteed fixes. As an Amazon Associate I earn from qualifying purchases.
Fitment Required · Vehicle-fitment part
Relevant when the code or supporting diagnostics point toward upstream or downstream oxygen-sensor faults.
This code family often involves upstream or downstream oxygen-sensor diagnosis.
Verify exact sensor position and vehicle fitment before buying.
View options on Amazon
Fitment Required · Vehicle-fitment part
Relevant when catalyst-efficiency or emissions faults persist after proper diagnosis.
Catalyst-efficiency faults sometimes point toward converter problems after proper testing.
Catalytic converters are highly vehicle-specific and should not be purchased by code alone.
View options on AmazonThese parts may be related to this fault category, but a code by itself does not confirm exact fitment or guarantee that replacing a part will solve the problem.