Code 26, Quad-Driver Circuit - 3.3L A & N Bodies: Notes

Fig 1: Code 26 Quad-Driver Circuit Diagram (3.3L A Body)

Courtesy of GENERAL MOTORS CORP.

Fig 2: Code 26 Quad-Driver Circuit Diagram (3.3L N Body)

Courtesy of GENERAL MOTORS CORP.

Each ECM Quad-Driver has a fault line which is monitored by the ECM. The ECM compares voltage values of the fault line with acceptable values in ECM memory. If the ECM senses other than accepted values, a Code 26 will set. QDM B will not set a Code 26.

1. The ECM does not know which controlled circuit set the Code 26. This tests SERVICE ENGINE SOON light driver and circuit.
2. QDM SYMPTOMS
   • TCC inoperative
   • Hot light on all the time, off during bulb check
   • Cooling fan on all the time or will not come on at all
   • Poor driveability due to 100 percent canister purge