Code 26, Quad-Driver Circuit 3.8L C & E Bodies: Notes

Fig 1: Code 26 Quad-Driver Circuit Diagram (3.8L C Body)

Courtesy of GENERAL MOTORS CORP.

Fig 2: Code 26 Quad-Driver Circuit Diagram (3.8L E Body - Reatta & Riviera)

Courtesy of GENERAL MOTORS CORP.

Fig 3: Code 26 Quad-Driver Circuit Diagram (3.8L E Body - Trofeo & Toronado)

Courtesy of GENERAL MOTORS CORP.

Each PCM Quad-Driver has a fault line which is monitored by the PCM. The PCM compares voltage values of the fault line with acceptable values in PCM memory. If the PCM senses other than accepted values, a Code 26 will set.

Some QDM circuits will normally cycle between high and low, such as depressing the brake pedal. Some "Scan" testers may set a false Code 26 if engine is running, tester is installed and brake pedal is depressed for more than 30 seconds.

NOTE: Test numbers refer to test numbers on diagnostic chart.

The PCM does not know which controlled circuit set the Code 26 so this chart will go through each of the circuits to determine which is at fault. This step tests SERVICE ENGINE SOON light driver and circuit.