I have a 2007 Saturn Sky Red Line. While at wot. boost dropped suddenly from 22lbs. to 14lbs. and engine light came on. Auto Zone found Error Code P2178. I disconnected the battery to reset the engine light but after driving easy for about 20 minutes it came on again. The only thing I did before this happened was fill up at Shell with 93 octane. Any ideas?
Thanks for the information. Now that AFR is mentioned I also noticed that the engine does not start as cleanly as before and there is a slight carbon rich odor. This all happened after I filled up with 93 octane at a Shell. Could it be some junk fuel?
Work the P2178 first. Running rich could be the A/F sensor or MAF faulty. Need to test by observing engine parameters with scan tool. Can you post the engine parameters/freeze frame data for the P2178? Could take a fuel sample if suspect bad fuel.
Potential causes for this code to set are: Faulty air/fuel ratio sensor/oxygen sensor (AFR/O2) Faulty mass airflow sensor (MAF) Rarely - faulty Powertrain Control Module (PCM) Read more: p2178