My truck has an Allison Transmission and won't shift out of park. Can someone please help me?

Question

Our truck is not shifting properly. It is showing shift range inhibited on the DIC. It's also throwing PO171 & PO174 codes. Are these related? Would it cause the Allison Transmission to do that? I'm stuck and need some help. Please!!!!!

Answer 1

Hi there

These codes are for a lean condition on bank 1 and bank 2 of the engine. These are not associated with the shifting issue. The shifting issue could be the result of a faulty brake light switch or a problem with the neutral safety switch. Check the brake lights and make sure they are working. If they aren't, then it's likely causing the problem of not shifting out of park.