You could have a bad Power train Control Module, (PCM), Body Control Module, (BCM) which is also referred to as the body control computer which you will see in the attached information, or the Programmable Communication Interface, (PCI) bus. In the attached information you will see that the BCM controls the VIC, Immobilizer or anti-theft system and the instrument cluster. The proper signal depends on the PCI. Another possibility is the CCD, see attached.
These modules or the PCI bus could be causing the vehicle to go into limp mode and then it explains the electrical light if the PCI bus has a transmission issue. Also the increased fuel consumption can be the BCM or PCM getting the wrong signal or they might be failing. It is hard to diagnose electrical problems as you have to start at one point in the circuit and trace it and test components on its path. The circuit is very seldom a 1 wire path but a parallel path.
The best place to start is to have the trouble codes pulled. Advance Auto or Auto Zone will do this for free.
Thursday, August 15th, 2013 AT 10:07 PM