P0840 - OBD II Trouble Code

Our automotive experts have put together the following information about the P0840 diagnostic trouble code. We've provided the common symptoms that occur when this code is set along with the frequent repairs that address the issues related to the P0840 code.

OBD II Fault Code

• OBD II P0840

OBD-II Code Transmission may not shift properly is defined as a Transmission Fluid Pressure Sensor/Switch "A" Circuit

The Transmission Fluid Pressure Switch allows the engine's control module (PCM) or Transmission Control Module (TCM) to use hydraulic fluid to engage the clutches in the transmission to allow for smoother shifting while driving. If the PCM or TCM detects an issue with the hydraulic clutch or the pressure switch, the PCM or TCM will set code P0840.

Transmission may not shift properly Symptoms

• Increased fuel consumption
• Transmission may not shift properly

Common Problems That Trigger the P0840 Code

• Transmission Control Module (TCM) failure
• Transmission fluid level is low
• Transmission fluid pressure sensor failure
• Wiring issue