I own a '94 FZJ80, I recently had it serviced at Toyota and was curious if the shop could have done something to the EGR system to make my code 71/PO401 to come on? I'll explain, I had a terrible leak on the back of the engine but couldn't tell or see the location of the leak. I took the truck to Toyota and they had to replace the valve cover gasket. My question is this, would it be possible of them to have knocked something loose inside the EGR or anything else to cause this code. I've not had any engine code prior to taking it in to the professionals. Any help or idea would be appreciated.