Q: 2008 chevy malibu code p0641

There are two 5 volt reference circuits for vehicle sensors (denoted circuit 1 and 2) each of which are monitored by the vehicle computer. When the code P0614 sets that means that the voltage on Circuit No. 1 is out of range (too far off from the nominal 5 volts), high or low. Typically, this is due to either a wiring fault (short, high resistance, etc.) but it can also be caused by an internally shorted sensor. Check your battery first though. A faulty battery will cause out of range voltages (on the low side, of course) and potentially set codes. On your car, the No. 1 five volt reference circuit supplies the manifold absolute pressure (MAP) sensor, the fuel tank pressure (FTP) sensor, the air conditioning (A/C) refrigerant pressure sensor, the accelerator pedal position (APP) sensor No. 2, and the intake camshaft position (CMP) sensor (this list should be confirmed with the wiring diagram prior to diagnostics). If it is a sensor issue (versus a wiring fault), unplugging sensors, one at a time, will show a large voltage change on the reference circuit as the circuit voltage is monitored on a scan tool and that can help narrow the diagnostic. As necessary, circuit wiring integrity must be checked, too. Typically, you will need to have in hand the factory wiring diagram from the Shop Manual to perform the required circuit traces. If you desire a speedy resolution, you can just request a Check Engine Light diagnostic and the responding certified mechanic will get the code resolved for you at your location. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.