Hi there,
P0170 indicates a fuel trim malfunction. If you have the P0171 with it, then it indicates a lean fuel mixture on bank 1. This can be the result of several items, but typically the front O2 sensor or the mass air flow sensor is to blame. Intake manifold vacuum leaks can cause it as well as exhaust leaks. P0171 TOYOTA - Air/Fuel Mixture System Lean Bank 1 Read more: https://www.autocodes.com/p0171_toyota.html
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