2005 BMW 645Ci Power Steering Control Module Replacement Cost

Power steering systems have developed over the past couple of decades, and are now responsible for assisting the driver with turning power and increasing subtlety at high speeds. To accomplish the first task, assisting with physically turning the wheels, mechanical components are sufficient. But, to assist with adding subtlety to steering at high speeds, an electronic means of control must be added. To control that system, the electronic power steering control module is used.

Electronic power steering is accomplished by placing a motor on the steering column or steering gear, and controlling the operation of that motor with, you guessed it, a control module. That control module will sense the position of the steering wheel, note which direction the steering wheel is turning, and how fast is is being turned. Also, the control module senses the speed of the vehicle, angle of headlights, and many other factors relating to driver control of the vehicle. It will then determine how much force to apply to the steering gear, what ratio it should turn the wheels at, and when to change those variables. This not only allows the driver to subtly or dramatically alter the path of the vehicle, but it allows the steering wheel to remain completely separate from the wheels.

Power steering control modules can fail causing a number of symptoms, including, but not limited to, power steering and other warning light illumination, steering wheel becoming stiff or nearly impossible to turn, speed sensitivity is no longer accurate, turning radius may seem to increase or decrease, an excessive number of turns of the steering wheel may be necessary to turn the vehicle. These result because the control module determines the ratio at which to turn the wheels. In other words, the steering control module will decide if turning the steering wheel a complete revolution will turn the wheels ten degrees or thirty degrees. It should be noted that erratic operation of the steering system or loss of steering ability is not common, but is possible.

Any issues with the power steering system should be addressed immediately when the vehicle uses electronic power steering assist. This is because many vehicles using electronic power steering do not have a steering wheel which connectes to the steering gear. Instead, these vehicles may use 'drive-by-wire' technology, and failure in these systems can be more dangerous than previous mechanically connected steering systems.

Power steering assist control module failure, like other electronic components, is random, and predictability is guesswork at best. Failure of this component is not as common as replacement, and this is because many manufacturers integrate the power steering control module into other control modules. Also, when the power steering assist motor is replaced, this can often call for replacement of the steering column, so the control module may be replaced as part of the assembly.

When diagnosing the power steering control module, the technician will simply compare actual conditions to electronic conditions. In other words, If the technician notes that the power steering motor is active, but the control module shows no voltage to the power steering assist motor, a discrepancy is noted. Discrepancies like this are commonly used as clues which map to the issue. If the technician finds that the issue originates with the control module, whether by physical or scan testing, the module will be verified defective and replaced.

Like any other control module, the location of the power steering control module will be identified, and the technician will then begin removing all obstructing components needed to access and remove the control module. Once accessed and removed, the connectors are cleaned and inspected, and the new module will be installed. After all components are reassembled on the vehicle, the technician will program the control module, if needed, and test the operation of the system to ensure the customer complaint has been corrected.

When dealing with electronic systems, especially if the issue pertains to the control module, we recommend thorough diagnostics before replacing parts. In effort to correct an electronic failure, it would be very easy to spend hundreds of dollars replacing components before realizing the issue is more advanced. In the case of electronic failures, diagnostics is a must.

Not all vehicles will have this component, and most vehicles with a power steering control module will also have electronic power steering. Except for some manufacturers, if the vehicle has a power steering fluid reservoir, power steering fluid pump or power steering fluid lines, it is unlikely that a power steering control module will be used. Also, be aware that most power steering control modules will likely be mounted on or near the steering column or the steering gear.

Except for the very advanced DIY mechanic with a strong understanding of computerized circuit diagnostics and testing, this repair should be left to a professional. Again, diagnostics of electronic systems are difficult for the untrained person to perform correctly. Unless safety and diagnostic methods are understood and followed properly, this should be left to a professional.