01 Stiff Pedal, Stalling Engine? 6 Potential Fixes for High RP… • 02 P0070: Ambient Air Temperature Sensor Circuit • 03 You Can Tell A Lot About A Car By Listening To Its Engine I… • 04 Electric Vehicles: The Future of Transportation Is Here, an… • 05 The Mitsubishi Outlander PHEV: A Plug-in Hybrid SUV That Ch… • 06 The Little-Known Reason Mechanics Don’t Always Reset Your E… • 07 P0116 – Engine Coolant Temperature Range Fault: Causes and … • 08 This Is Why The Air Recirculation Button Is So Important • 09 Why Does Your Car Shake When Braking at High Speeds? • 10 Is Your Car Burning Oil? Signs & Solutions for Oil on Spark… •

DTC codes / BMW codes / P1734

P1734 · BMWPressure Control Solenoid B Electrical

P1734 on a BMW means the transmission control module has detected an electrical fault in the circuit for pressure control solenoid B, which is one of the electro-hydraulic valves that regulates hydraulic pressure inside the automatic gearbox. The computer monitors the solenoid's electrical circuit for open circuits, short circuits, or out-of-range resistance and sets this code when the expected current or voltage does not match what it commands.

SystemPowertrain
Code typeBMW specific
SeverityHigh
Fix difficultyProfessional
AreaTransmission

Symptoms you may notice

  • Illumination of the transmission malfunction warning light or check engine light
  • Harsh or delayed gear shifts, especially when the transmission is cold
  • The gearbox may enter limp mode and stay in a single gear or neutral
  • Slipping or flaring during upshifts or downshifts
  • Often no symptoms besides the warning light if the electrical fault is intermittent
  • Rough engagement when selecting drive or reverse

Common causes, most likely first

  1. Faulty pressure control solenoid B itself, with an open or shorted internal coil
  2. Damaged or corroded wiring harness or connector at the transmission valve body
  3. Transmission fluid contamination or degradation causing solenoid sticking and abnormal current draw
  4. Valve body wear or debris blocking the solenoid's hydraulic circuit
  5. Loose or damaged ground connection for the transmission control module
  6. Internal fault in the transmission control module (mechatronics unit) driver circuit
  7. Low transmission fluid level due to a leak, causing aeration and erratic solenoid operation

How to diagnose and fix it

  1. Scan all modules with a BMW-capable diagnostic tool and record freeze-frame data and any companion codes before clearing anything
  2. Check transmission fluid level and condition according to BMW's specified procedure for the gearbox fitted
  3. Inspect the transmission wiring harness and connector for chafing, corrosion, or pushed-out pins
  4. Measure the resistance of pressure control solenoid B at the valve body connector and compare with BMW's specification
  5. Perform a voltage drop test on the solenoid's power and ground circuits while commanding the solenoid with the scan tool
  6. If electrical integrity is confirmed, remove the valve body and inspect solenoid B and its hydraulic passages for debris or wear
  7. After repair, clear adaptations and perform a relearn drive cycle, then verify the code does not return

What BMW technicians check before replacing solenoid B

  • A P1734 is frequently caused by a chafed harness section near the transmission bellhousing or a corroded connector pin rather than by the solenoid itself, so always inspect the wiring before condemning the valve body.
  • On many BMW gearboxes the pressure control solenoids are part of the mechatronics assembly, and replacing just the solenoid without addressing contaminated fluid or a worn valve body often leads to a repeat failure.
  • An intermittent P1734 that appears only when the transmission is hot can be caused by a solenoid coil that changes resistance with temperature, which will not show up on a cold resistance test.
  • Low fluid level or aerated fluid from a slow leak can mimic a solenoid electrical fault because the solenoid current fluctuates when it is not fully submerged in fluid.
  • Do not overlook the transmission control module ground and power supply, since a poor ground can set multiple solenoid circuit codes including P1734 without any fault in the solenoid itself.

Can I keep driving with P1734?

If the transmission is in limp mode or shifting harshly, avoid driving because continued operation can cause internal mechanical damage. If the only symptom is the warning light and the car drives normally, you can drive cautiously to a workshop for diagnosis, but do not tow heavy loads or drive at high speed.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for BMW vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

Running on fumes Free guides aren't free to make. Top up the tank. Any amount, one time. Fuel the Garage