GM OBD Trouble Code 28

By Jim Taddei, May 1, 2009

Auto Transmission Range Pressure Switch Error

The Auto Transmission Range Pressure switch is generally located inside the transmission, attached to the valve body. This switch uses hydraulic pressure to signal the ECM as to which gear the transmission is in.

Fault Code Description

  • 28 - Auto Transmission Range Pressure switch error


  • No symptoms may be noted or the transmission could shift erratically

Common Problems

  • A failed Transmission Range Pressure switch is the most common cause for a code 28

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