Code 23 is a TPS code. Out of self test range. In the link above it requires an adjustment of the TPS if its Out of range. I just like to cover all the bases. If his idle was set too low, it may have the TPS voltage out of range. He could possibly just raise the IDLE screw and Kill 2 birds with one stone(Idle problem and TPS code). But Im not sure. Thats why its easier to go through the whole process. For me anyways.:bigthumbsupSounds more like a TPS problem.