I have a 91 Buick Century limited 3.3L with a 3300 engine. I ran a diagnostic scan of which produced the two-digit codes 12, 26, and 27, and In attempting to look up these codes, I found a website on...
DTC 26 and 27 refers to a QDM (Quad Driver Module) fault.
The Quad Driver is a "safety valve" for the ECM controlled circuits, the quad driver controls up to 4 circuits.
There are multiple quad drivers in the ECM. The QDM shuts down a shorted circuit to prevent high current flow from damaging the ECM. So the DTC 26 or 27 will isolate the problem to 1 QDM. You will need a repair manual with electrical diagrams and DTC flow charts to determine which of the circuits controlled by that QDM are failing.
Usually DTC 26 refers to the Torque Converter Clutch solenoid and related circuit. Most likely you have a shorted TCC solenoid or the harness connected to it, The solenoid is internal in the transmission accessible from the side cover.
Also, keep in mind the single most cause for any code will be a power or ground problem. Clean all the battery cables, and any and all cables or wires that attach from the engine to the firewall.
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Nov 28, 2011 |
1991 Buick Century