What does it mean?
SPECIAL NOTES: Non-professional mechanics should take note that although code P0639 “Throttle actuator control, bank 2 -range/performance problem” is sometimes repairable on a DIY basis, this code is often the result of failures, malfunctions, or defects in the CAN (Controller Area Network) bus system that may not be directly related to the throttle actuator.
In simple terms, the CAN system can be thought of as a sort of intranet that connects the sometimes-several dozen control modules that control every imaginable electrical function on a modern vehicle. To complicate matters, this system is composed of literally thousands of circuits that are interconnected by tens of thousands of connections in an incredibly complex system that most generic code readers cannot access.
The net result of this is that in some cases, code P0639 may be the only code a generic code reader can display, when in fact, there may be other CAN system related codes present that cannot be displayed.
In such cases, code P0639 may only be the result of other, inaccessible codes, which means that if the few generic diagnostic/repair steps outlined in this guide do not resolve code P0639, the wisest option would be to refer the vehicle to the dealer, or other competent repair shop for professional diagnosis and repair.
In light of the above, non-professional mechanics should take note that this guide cannot provide detailed diagnostic and repair information for this code, other than a few generic steps that may, or may not resolve code P0639. In the event that the information provided in this guide does not resolve P0639, suspect a more serious failure, malfunction, and/or defect in the CAN bus system. END OF SPECIAL NOTES.
OBD II fault code P0639 is a generic code that is defined as “Throttle actuator control, Bank 2 -range/performance problem”, and is set when the PCM (Powertrain Control Module) detects a problem with the operation of the throttle control actuator on drive-by-wire systems.
In this definition, “range/performance problem” refers to the fact either that the throttle control actuator does not perform as expected given a particular set of operating conditions, or, that the actual throttle position does not agree with the desired throttle position given a particular set of operating conditions. “Bank 2” refers to the bank of cylinders that does not contain cylinder #1 on engines with two cylinder heads.
Note that on some applications, as many as eight failure cycles need to occur before the PCM will store a trouble code and illuminate a warning light.
On systems that use drive-by-wire technology, there is no physical link between the accelerator pedal and the throttle, and throttle control on these applications is accomplished with a stepper motor that is “instructed” by the PCM to open or close the throttle, using input data from several control modules, which might include the following- transmission control module body control module ABS control module fuel control module turbo control module cruise control module traction control module stability control module proximity alert module On some applications, there may be other control modules involved, but in all cases, the process of controlling the throttle starts when the driver depresses the accelerator pedal.
A position sensor in the pedal assembly communicates both the position of the pedal, and the rate at which the pedal is being depressed. This basic information is transmitted to the PCM via the CAN bus system, but also to all other affected modules (see list above).
Moreover, this information is also shared between all affected modules and the PCM via feedback circuits to ensure that all affected modules that are involved with the safe operation of the vehicle “know” that a throttle input had been made. However, before the application will actually begin to accelerate, the PCM will verify that all affected control modules have received the throttle input data, and that all affected m