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Home >> GMC >> 1991 >> Forward Control 4.3 Z, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes - Transmission >> Component Check Charts >> Output Speed Sensor Circuit Check (2WD - "C" & "K" Series) >> Notes

Output Speed Sensor Circuit Check (2WD - "C" & "K" Series): Notes

The output sensor circuit consists of a magnetic induction-type sensor, digital ratio adapter located in the instrument cluster, and wiring. Gear teeth pressed on the outside diameter of the output carrier assembly induce an alternating current in the sensor.

This current is transmitted to the instrument cluster, where it is passed on to the PCM. The digital ratio adapter compensates for various axle ratios, and converts the signal to a square wave for use by the speedometer, cruise control and anti-lock brake system.

NOTE: Test numbers refer to test numbers on diagnostic chart.
  1. This test verifies output speed sensor voltage at PCM.
  2. This test directly verifies operation of output speed sensor.
  3. This test checks circuits No. 821 and 822 up to the instrument cluster.
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