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Home >> GMC >> 1995 >> Forward Control 6.5 Y, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes - 6.5L Diesel. >> Diagnostic Trouble Code Charts >> DTC 23, App No. 1 Circuit Range Fault >> Notes
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DTC 23, App No. 1 Circuit Range Fault: Notes

Accelerator Pedal Position (APP) module provides a voltage signal that changes relative to accelerator position. There are 3 sensors located within APP module that are scaled differently. DTC 23 will set when PCM has recognized a skewed (mis-scaled) sensor. PCM compares all 3 sensors to each other and determines if there is a 6 percent difference between APP No. 1 and APP No. 2, and a 10 percent difference to APP No. 3.

PCM will default to input from APP No. 1 sensor being ignored. A current and history DTC will set but will not turn on SERVICE THROTTLE SOON light. Throttle will operate normally as long as there is only one sensor malfunctioning. If 2 different APP sensors have a malfunction, SERVICE THROTTLE SOON light will light and PCM will limit power. If 3 APP sensors malfunction, SERVICE THROTTLE SOON light will light and PCM will only allow engine to operate at idle.

NOTE: Test numbers refer to numbers on diagnostic chart.
  1. This step determines if a good 5-volt reference is present.
  2. This step checks for an open in ground circuit.