Code 26 - Quad-Driver Error, (2 Of 3)
The ECM regulates its control devices by turning on and off circuits called "Quad-Drivers" The ECM also monitors each of these circuits by means of a fault line. When the driver is not being energized by the ECM there should be 12 volts present on the fault line. When a driver is energized by the ECM, the fault line will drop to near zero volts. If 12 volts is not present due to an open or shorted control circuit or an open component coil, or if the ECM does not recognize the low state, Code 26 will set in memory.
This chart determines which circuit is out of specification. All circuits EXCEPT "B1", the "SERVICE ENGINE SOON" light, "A18", and the hot light should have battery voltage when the key is on, engine not running and the ALDL "test" connector is not grounded.