P0840 Code - Transmission Fluid Pressure Sensor/Switch 'A' Circuit

Discussion in 'P - Powetrain Codes' started by fault code, Mar 26, 2018.

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    fault code Administrator Staff Member

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    What does P0840 Mean?

    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.

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    What are the common causes of P0840 ?

    Common causes include a faulty electronic pressure control solenoid, transmission fluid pressure sensor, hydraulic blockages inside the internal transmission fluid passages, mechanical internal transmission failures, low transmission fluid, dirty or contaminated transmission fluid, a faulty PCM or transmission control module.

    View attachment 498

    How do you troubleshoot P0840 ?


    With the valve disconnected, the red voltmeter lead should be attached to the IMRC valve power wire and the black voltmeter lead connected to ground. If all testing has passed so far yet you still have the same code, check your scan tool and see if it can open and close the IMRC valve. If the engine displays a miss and there wasn't a code, determine which cylinder is misfiring. If the exhaust manifold is visible, spay or pour a small amount of water on each cylinder exhaust port. Water will evaporate immediately on good cylinders and slowly on the missing cylinder. If this can't be accomplished pull the plugs and check the condition.

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