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GM OBD Trouble Code 79

By Jim Taddei, May 1, 2009

Transmission fluid over temperature

The ECM monitors the automatic transmission fluid temperature via the transmission fluid temperature sensor. If the transmission fluid reaches a predetermined limit, code 79 will be set.

Fault Code Description

  • 79 - Transmission fluid over temperature

Symptoms

  • Transmission shifts may become more firm in an attempt to avoid slippage.

Common Problems

  • Low transmission fluid level
  • Transmission slipping

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