P0991 OBD II Trouble Code Transmission Fluid Pressure Sensor Switch E Circuit Intermittent

How to diagnose, repair, and info on causes of a P0991 transmission trouble code related to the trans fluid pressure sensor switch E Circuit that is intermittent.

Symptoms of P0991 OBD II Trouble Code

  • Malfunction Indicator Light On
  • Change in shift quality
  • Vehicle starts off in 2nd or 3rd gear (limp in mode)

Common Causes of P0991 OBD II Trouble Code

  • Intermittent open in the signal circuit to the TFPS sensor
  • Intermittent short to voltage in the signal circuit to the TFPS sensor
  • Intermittent short to ground in the signal circuit to the TFPS sensor
  • Failed TFPS Sensor ? likely
  • Internal mechanical transmission issue - possible
  • Failed PCM - unlikely (programming required after replacement)

Severity of P0991 OBD II Trouble Code

Severity depends upon which circuit the failure has occurred in. Since this could be an electrical failure or a mechanical failure, the PCM/TCM can compensate to some degree. The failure may mean that the PCM/TCM modifies the shifting of the transmission if electronically controlled.