Error code P0499

I cannot tell if you are stating what the mechanic wrote on the repair order or if that is what you did. The problem is diagnostic fault codes never say to replace parts or that one is bad. They only indicate the circuit that needs further diagnosis. In this case the code is caused by a break in the circuit, and that is most often due to a corroded connector terminal. Next would be a cut wire or a bad pump motor. The last thing on that list would be the engine computer. It tried to run the pump but detected the open circuit.

I wasn't clear in my explanation. The computer can detect hundreds of defects, and the fault codes get very specific as to which circuit has the problem. Don't worry about the battery cables and things like that. This code refers to the wires related to the leak detection assembly, and that assembly. Specifically, terminal number 8 at the Engine Computer is a white / dark green wire going to the leak detection assembly. That wire can have a break or cut in it, but a corroded or stretched connector terminal is a better suspect. The leak detection assembly also has a ground wire that competes the circuit that has the problem, therefore, that black wire also needs to be checked for breaks or a corroded terminal where it bolts to the body. This ground is listed as being near the battery. That is a good place to find a corroded connection from acid leaking from a battery that's about to fail.

The Engine Computer is part of this circuit too, but they cause very little trouble. Even the terminals in that connector are very reliable, so those should be the last suspects after everything else is ruled out.