After making a pcb for my friends car, I started to look at more info on the OBDII standard used most cars built after 1996. By tapping into the OBDII system, you are able to view and control many different parameters in a car. While interfacing into OBDII systems is possible with a PIC, it seems much simpler to use an OBDII IC that takes care of most of the protocol. There are a few IC’s on the market that range from $8-20, but I was able to get my hands on a few samples for free from OBDSolutions. The chip is basically and OBDII to RS232 interpreter, allowing control over various car sensors and DTC codes. When the fans quit working on the Malibu, a DTC code showed the problem was that the fan relays had failed. By simply unplugging the ETC sensor it trips an error in the ECU that activates both fans immediatley. Since both fans came on we knew the relays were working fine. By checking the internet I found a lot of these cars have this problem. It has something to do with ECU burning on a certain section of the pcb.