how to fix transmission codes P0700 to P0799 in BMW 3 Series E90/E91 (2005-2012)

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Ensure the vehicle is on a level surface and securely lifted with jack stands if necessary.
• Disconnect the negative battery terminal to avoid electrical shorts.

2. Transmission Fluid Change

1. Drain the Old Fluid

   • Remove the transmission drain plug and allow the fluid to drain into a container.
   • Replace the drain plug once all fluid has drained.

2. Replace the Filter

   • Remove the transmission pan by unscrewing the bolts.
   • Carefully detach the pan and replace the transmission filter.
   • Clean the pan and ensure the magnet is free of debris.

3. Add New Fluid

   • Reinstall the transmission pan with a new gasket and torque the bolts to manufacturer specifications (typically around 8-10 Nm).
   • Add the appropriate type and amount of transmission fluid (refer to the owner's manual, usually ATF Dexron III or suitable equivalent).

3. Electrical Check

1. Inspect Wiring and Connectors

   • Visually inspect the wiring harness for any signs of fraying or damage.
   • Clean and secure any corroded connectors to ensure proper electrical connection.

2. Test Transmission Control Module

   • If necessary, reprogram or update the transmission control module using specialized software if there are known updates from BMW.

4. Valve Body Inspection

1. Remove Valve Body
   • If issues persist, remove the valve body by unscrewing the necessary bolts and carefully lifting it out.
   • Inspect for any worn or damaged solenoids and replace as needed.

5. Reassembly

• Once repairs are completed, ensure all components are reassembled correctly.
• Reconnect the negative battery terminal.