B0840 BMW Fault Code

Description:

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 BMW PCM or TCM will set code B0840

B0840 Code Symptoms :

The B0840 Check Engine lamp is perhaps the most troubling of lights because it could mean so many different things, from you didn't screw the gas cap on tightly enough to look out for pistons flying through the hood and into the stratosphere. The easiest way to find out what this light is telling you is to hook your vehicle up to a scan tool. B0840 diagnostic tool looks a little like an oversized calculator and plugs into a communication port inside the car. After you instruct it to perform the scan, it speaks with your car's computers to find out exactly what's prompting the light to turn on.

Diagnosis And Repairing B0840

B0840 OBD2 may also be triggered by faults earlier down the line. For example, a dirty MAF sensor might be causing the car to overcompensate in its fuel-trim adjustments. As a result, oxygen sensors are likely to report fuel mixture problems.

How to fix B0840 code ?

• Exhaust tube
• Damaged ECM
• Fuel tank leaking
• Foreign matter caught in fuel filler cap

In most cases, the TCM is integrated into a single housing with the BMW PCM. Nevertheless, the section of the module which controls (automatic) transmission function may be powered up separately.

In any case, the TCM is typically powered using switched (only present with the ignition switch in the ON, start, or run position) voltage. This circuit is normally equipped with a fuse, fusible link, and/or a relay. Frequently, the PCM and TCM are powered using the same relay albeit by separate circuits. Access to a reliable vehicle information source will yield necessary details of the TCM power circuit for the specific vehicle in question.