Tripac APU Eng Code Help!

Eng code appears about 10 seconds after I press the APU button. I have tried turning off/on the APU, reseting it, and checking the fuses, but nothing. I am guessing the problem may be the wiring. What is strange is that my APU was working yesterday, but after 11 hours of driving, I noticed it was already on ENG code.

 

I should add that the Eng code comes on so fast it won’t even let the APU engine start.

 

Well, I took it to TK, and the problem was a corroded wire behind the on/off switch inside the APU housing. I need to start inspecting all the wires for corrosion on both my APU and truck. The bill was $500. It’s always hundreds of dollars with those guys. I’m gonna clean all my wires with a wire brush and put some grease on them so hopefully they won’t corrode too easily.

 

Inside the APU. There are actually lots of wires. Water seems to find its way inside the APU and mess up the wires, I think.