2003 Cadillac Seville.The codes are P0171 & P0174. Also cutting out at low speeds. Had the same two problems over a year ago. Was fixed by replacing the intake plenum coupler and the CPS. Are the two related? I'm just confused why I'm having the same two issues again at the same time. Any ideas?

 

If the P0171 is combined with the P0174 code, it's very likely that the problem is caused by an intake leak. If there are no intake leaks, the next step is to replaced the air filter and clean the air flow meter. If the problem persist the front oxygen (O2) sensor may need to be replaced.