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Code 26, Quad-Driver Circuit 3.8L: Notes

WARNING: This page does not describe the selected car, but rather 24 other vehicles, including the 1993 Pontiac Trans Sport, 1993 Oldsmobile Silhouette, 1993 Oldsmobile Bravada, 1993 GMC Vandura, and 1993 GMC Value Van. However, it is still accessible from the selected car via links, so may be relevant.

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

Some QDM circuits will normally cycle between high and low, such as when brake pedal is depressed. 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 number refers to number on diagnostic chart.
  1. PCM does not know which controlled circuit set Code 26, so this chart checks each circuit to determine which is at fault. This step tests SERVICE ENGINE SOON light driver and circuit.
  2. This determines which circuit is out of specification.
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