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First off, are these fuel trim readings at idle or while driving? But the -17 indicates that you are running rich, -25% is max and ideally you want to be close to 0% at all times. You mentioned that you were losing fuel pressure with the key on and the engine off. Leaky injectors could cause you to run rich for sure but there are many other possibilities as well. Your fuel pressure shouldn't be decreasing like that and I would start troubleshooting that first. I agree with what you said about it affecting both banks but you never know you might have more then one leaky injector. Currently I am dealing with running lean in my truck (+25% fuel trims) so i have been doing a lot of research on fuel trims haha.

I would look up the codes PO172 and PO175 and take a look at the common causes. I don't believe these codes would come on until you hit the max of -25% but you are getting close and the same would apply.
 

ForaBot's answer is created from summarizing the responses in this thread.

Based on the information provided by members of the community, it is correct to assume that since both banks are reading the same, the issue is likely something that affects all cylinders and not something like a bad injector. Short term fuel trims should be close to the same numbers as long term fuel trims, and ideally should be 0%. Positive readings mean the engine has to add fuel, indicating a lean condition, while negative readings mean the engine is subtracting fuel indicating a rich condition. Long term fuel trims use the fuel trim table to determine how to control the short term, and can take time to adjust.
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GMT604 said:
If you clear the memory, idling for about ten minutes should tell you.
Should short term fuel trims and long term fuel trims be close to the same numbers? I haven't been able to find an answer to this question but aren't the long term fuel trims just an average over a longer period of times and the short term is real time data? Or am I thinking of this completely wrong? Its not making sense that my short term trims are bouncing around from 0 to +7 while my long term trims are +20 to +25. Maybe a reset is in order? I will fully understand these trims someday haha.
 
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