Faulty secondary pressure solenoid, including a worn coil or stuck valve inside the solenoid; Damaged or corroded wiring harness between the TCM and the solenoid, often due to heat, oil contamination, or chafing; Loose or corroded electrical connector at the solenoid or at the transmission case pass-through; Low or contaminated transmission fluid causing pressure deviations that the TCM interprets as a communication fault; Internal transmission mechanical wear, such as a sticking valve body or worn seals, that prevents the solenoid from achieving commanded pressure; A failing TCM or a software issue in the transmission control module; Aftermarket or incorrect transmission fluid that alters hydraulic behavior and triggers the monitoring logic

DTC codes / BMW codes / P1749

P1749 · BMWSecondary Pressure Solenoid Communication Error

Q: What does code P1749 mean?

Secondary Pressure Solenoid Communication Error. P1749 on a BMW indicates that the transmission control module (TCM) has lost reliable communication with the secondary pressure solenoid, which is responsible for regulating hydraulic pressure inside the automatic gearbox. The TCM monitors the solenoid's electrical circuit and expected pressure response, and it sets this code when the signal is missing, intermittent, or outside the expected range.

P1749 on a BMW indicates that the transmission control module (TCM) has lost reliable communication with the secondary pressure solenoid, which is responsible for regulating hydraulic pressure inside the automatic gearbox. The TCM monitors the solenoid's electrical circuit and expected pressure response, and it sets this code when the signal is missing, intermittent, or outside the expected range.

SystemPowertrain

Code typeBMW specific

SeverityMedium

Fix difficultyProfessional

AreaTransmission

Symptoms you may notice

Illumination of the transmission warning light or check engine light, often with no other noticeable symptoms at first
Harsh or delayed gear shifts, particularly when the transmission is cold or under load
The transmission may enter limp mode, sticking in a single gear or refusing to shift
A noticeable clunk or jolt when selecting Drive or Reverse
Reduced fuel economy and higher engine rpm at cruising speed due to improper shift points

Common causes, most likely first

Faulty secondary pressure solenoid, including a worn coil or stuck valve inside the solenoid
Damaged or corroded wiring harness between the TCM and the solenoid, often due to heat, oil contamination, or chafing
Loose or corroded electrical connector at the solenoid or at the transmission case pass-through
Low or contaminated transmission fluid causing pressure deviations that the TCM interprets as a communication fault
Internal transmission mechanical wear, such as a sticking valve body or worn seals, that prevents the solenoid from achieving commanded pressure
A failing TCM or a software issue in the transmission control module
Aftermarket or incorrect transmission fluid that alters hydraulic behavior and triggers the monitoring logic

How to diagnose and fix it

Scan all modules with a BMW-capable diagnostic tool to confirm P1749 is current and check for related transmission codes
Inspect the transmission fluid level and condition, looking for dark color, burnt smell, or metal debris
Visually inspect the solenoid wiring harness and connectors for chafing, corrosion, or oil intrusion, and perform a wiggle test while monitoring live data
Measure the resistance of the secondary pressure solenoid at the connector and compare it to the manufacturer's specification
Check the solenoid's electrical circuit for shorts to ground or power and for excessive voltage drop under load
If electrical checks pass, remove the transmission pan and inspect the solenoid and valve body for contamination or mechanical sticking
Replace the faulty solenoid or repair the wiring as needed, then clear the code and perform a transmission adaptation reset and road test

What the pressure solenoid code hides

A communication error does not always mean the solenoid is dead; a poor ground or a voltage drop in the shared power feed can mimic a failed solenoid and fool a parts-swapping diagnosis.
On many BMW transmissions, the secondary pressure solenoid shares a connector with other solenoids, so oil wicking through the harness can cause intermittent faults that only appear when the transmission is hot.
Low fluid level from a slow leak often sets this code before the driver notices any shifting problem, so always check the fluid level and pan for seepage before condemning electrical parts.
The TCM may set P1749 as a consequence of a mechanical pressure problem, such as a sticking valve body, even when the solenoid itself tests good on the bench.
Clearing the code without performing the transmission adaptation reset can leave the TCM with old shift learning values, causing the code to return immediately after repair.

Can I keep driving with P1749?

You can usually drive the vehicle to a workshop if the transmission still shifts and the warning light is steady, but avoid heavy acceleration, towing, or long highway trips. If the transmission enters limp mode or shifts harshly, stop driving and arrange a diagnostic scan to prevent further internal damage.

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.