The Quad Driver Module is the part of the PCM that switches grounds to certain components when necessary. Some examples of these components are the Check Engine light, cooling fan, TCC solenoid, etc. Code 26 is a gereral code meaning that the voltage is not correct on one or more circuit. Unfortunately, the PCM will not tell you which specific component to check so a manual that is specific to your year will be very helpfull. You can order a Factory Service Manual from
www.helminc.com . They are only $30 through April 31 instead of the usual $90 so order fast.
Some causes for this can include a faulty PCM, poor connections at PCM, blown fuses or shorted circuits or solenoids. The QDM is protected internally and works like a circuit breaker. Say for instance, the wire that grounds the cooling fan relay is frayed and shorting out on some bare metal. This would cause the fan to run when the ignition is on and throw a Code 26 because the PCM is seeing a ground in that circuit when it should be +12v.
Confused? It can be. That's why the FSM is so important if you are going to tackle this problem yourself.
04-26-2005, 05:27 PM
