Code 26 - Quad-Driver Error, (1 Of 3): Notes

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, an open component coil, or if the ECM does not recognize the low state, Code 26 will set in memory.

The ECM does not know which controlled circuit caused Code 26 to set, so this diagnostic chart series will go through each of the circuits to determine which is at fault. An EGR circuit problem should also set a Code 32, however, after repairing the EGR fault, Code 26 chart should be performed.