Are you getting rich or lean mixture codes?
The mixture issue can be caused by various components, it can also be triggered by faulty wiring to a given component. So even if you were to replace that part it will not fix the issue as the problem will still exist.
Let me know what are those code numbers. This can help us diagnose the issue and find a solution.
As for the diming of headlights, it can be due to low alternator output or faulty wiring.
Test the alternator to see if it is producing the right amount of output to the battery.
Here is a helpful guide of how to test the alternator:
Please let me know of any questions.
Images (Click to enlarge)
Friday, September 10th, 2021 AT 1:23 PM