So, My GF’s 2003 Tacoma SR-5 4x4 extra-cab (3.4l V6, auto) has been throwing code P0456 “Evaporative emissions leak detected (very small leak)“. None of the mechanics that have looked at it have been able to find the leak and they’ve all just shrugged, reset the MIL and moved on. This includes the Toyota dealer. Last autumn they replaced her rusty frame under the terms of her extended warranty and tried to track it down then too. The best they could come up with is “we can try replacing your fuel tank ($800) and see if it goes away...” or “we can just reset the light again...”

It goes away in cold weather, and never throws the code as long as the ambient temperature stays below about 40 degrees F. Now that spring is here, so is the code. It comes back within 2 or 3 drive cycles, and near as we can tell doesn’t care how full the gas tank is.

The gas cap, filler tube and purge valve have been replaced. Any “classic” places this could be coming from or are we just destined to keep resetting the light until the leak gets big enough to detect with a sniffer?