I recently reset my fuel trims to 0 out long term trim, and I observe the short term trim bank 1 bounces from -25% to -10%. Bank 2 is generally +/-10%.
But based on the A/F sensor, Bank 1 has a much lower voltage, suggesting it is running more lean. Whether it is or isn't seems irrelevant, as my understanding is if the A/F sensor is reading low, this should trigger a positive fuel trim, not consistently negative ones, especially given that Bank 2 seems to be functioning at normal levels. Are there other sensors that impact the fuel trim that could explain this?
Other info:
- 2004 Nissan Armada
- The upstream B1 cat was replaced about 18 months ago and was leaking at the exhaust manifold gasket
- I've had this problem of lower B1 A/F voltage for years.
- I've replaced both the A/F and downstream O2 sensors on Bank 1, PCV valves
- I didn't find any vacuum leaks with the smoker
