P2106 – Throttle actuator control (TAC) system – forced limited power mode

Reinier

By Reinier (Contact Me)
Last Updated 2017-01-24
Automobile Repair Shop Owner

Trouble CodeFault LocationProbable Cause
P2106 Throttle actuator control (TAC) system - forced limited power mode Wiring, TAC motor, APP sensor, ECM

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What Does Code P2106 Mean?

OBD II fault code P2106 is defined by all manufact6urers as “Throttle actuator control (TAC) system – forced limited power mode”, and can be set when a fault occurs in the Throttle Actuator Control system on applications that employ drive-by-wire throttle control, or when the PCM (Powertrain Control Module) on such an application detects a fault in any other system, component, or controller that requires that a fail-safe, or limp mode be initiated to prevent further damage to the affected system, component, or controller.

Typical examples of this code setting as the result of failures and defects that do not involve actual throttle control could include the following, but take note that the few examples listed here does not represent a complete or exhaustive list of all possible examples. Always refer to the affected application’s manual for detailed information on all possible causes that could produce a fail-safe mode on that application.

– Engine overheating

When the PCM detects an abnormally high engine temperature on some applications, it could initiate a fail-safe mode by disabling both the ignition and fuel injection systems on some cylinders. This measure allows the intake air to absorb and carry away some of the engine’s heat by passing it through the exhaust system. The number of cylinders that can be disabled at any given moment depends on the application, and the degree of overheating.

– Coolant leaks

On some applications, such as some GM products, the PCM will initiate a fail-safe mode if it detects a significant loss of engine coolant. The advantage of this should be obvious, since the likelihood of the engine over heating is reduced, if not eliminated.

– Modifications to the drive axle

Altering final drive gear ratios or fitting oversized road wheels can cause the PCM to “detect” over -, or under speed conditions in the engine and/or transmission. In these cases, the PCM (and possibly other controllers) need to be reprogrammed to recognize the different ratios or wheel size(s). It is worth noting at this point that on some AWD applications, even a slight size difference between the front and rear wheels can trigger a fail-safe mode.

– ABS, Traction Control, Stability Control failures

It should be noted that whether or not a fail-safe mode is initiated when P2106 sets on some applications depends on the application as much as it does on the exact nature of the problem. Since both traction and stability control share many ABS components, including the wheel speed sensors, a problem in one or more wheel speed sensors can set this code and trigger the warning lights for all three systems, depending on the application.

– Automatic transmission problems

While the actual transmission problems that can trigger a fail-safe mode vary greatly between applications, three common problems are slipping transmission components, abnormally high transmission temperatures, and communication issues/failures between the transmission control module and other control modules.

– Abnormal system voltages

Although it is relatively rare for abnormal system voltages to be the root cause of a fail-safe mode, both low and high system voltages can damage one or more control modules. If this happens, the PCM could initiate a fail-safe mode when damaged controllers interrupt communication between controllers on the CAN (Controller Area Network) bus system.

In the examples listed above, the PCM may severely limit throttle response; in fact, it would be fair to say that the PCM effectively takes control of both throttle inputs and throttle response in order to prevent further damage to systems, components, or controllers from occurring, or to prevent potentially dangerous situations from developing that may be beyond an average driver’s ability to control or correct.

Fortunately, though, some causes of code P2106 are more mundane, such as failures of the stepper motor and/or the position switch (es) in the throttle control mechanism, or sometimes just carbon build-up in the throttle body that prevents free movement of the throttle plate throughout its range of movement. Many Ford applications are particularly susceptible to the latter problem and in most cases where this code is present on a Ford product, the problem is easily resolved simply by cleaning out the throttle body with an approved solvent to remove the carbon deposits.

What are the common causes of code P2106?

As stated elsewhere, the cause(s) of code P2106 does not have to involve the throttle control system, except in cases where it is certain that there are no other codes present along with P2106.

In cases where other codes are present, refer to the application’s repair manual for detailed information on the implications of all recorded codes for that application.

What are the symptoms of code P2106?

Symptoms of code P2106 could include the following-

  • Stored trouble code and illuminated warning light(s)
  • Little, or no throttle response
  • Automatic transmission may not shift at all
  • Additional codes will be present along with P2106, but take note that any symptom(s) not listed already will be dependent on the application, as well as on the actual problem(s) that caused code P2106 to be set, and a fail-safe mode to be initiated.

How do you troubleshoot code P2106?

SPECIAL NOTES: Code P2106 is an “informational” code, and in many, if not most cases, this code’s only function is to alert a driver that the PCM has initiated a fail-safe mode due a malfunction or failure in a system that is very often not directly related to the Throttle Control Actuator in any way. Unless it turns out that the throttle actuator (or its control system) is actually defective, the only other reason why the throttle actuator is referred to in the code definition at all is because a fail-safe mode can most easily be accomplished by “disconnecting” the throttle actuator from the accelerator pedal.

In practice, this means that once this code is set, the application is forced into a fail-safe mode and the engine will NOT respond to throttle inputs made by the driver. Non-professional mechanics should therefore take note that if code P2106 is present on a vehicle and the code definition displayed on a cheap, generic code reader does not include a reference to a specific system or component, that code reader will almost certainly not be able to extract manufacturer specific codes from the OBD II system, and especially not codes that involve the CAN (Controller Area Network) bus system.

Put in another way, if only code P2106 is displayed on any code reader or scanner, it means that the root cause of P2106 can likely not be diagnosed with that reader/scanner. Therefore, in cases where suitable diagnostic equipment is not available, the wisest option is to refer the vehicle to the dealer or other competent repair shop for professional diagnosis and repair.

In light of the above, it must be understood that this guide cannot provide detailed diagnostic and repair information for code P2106 that will be valid for all applications under all possible conditions. Non-professional mechanics should therefore always consult the manual for the application for detailed information on the exact definitions of all codes (including pending codes), as well as their relationship to each other, and to P2106. END OF SPECIAL NOTES.

Step 1

If suitable diagnostic equipment is available, record all fault codes present, as well as all available freeze frame data. This information could be of use should an intermittent fault be diagnosed later on.

NOTE: Pay particular attention to “soft” or pending codes during the scanning process. While it is highly unlikely that one or even two pending codes will initiate a fail-safe mode, one or two pending codes in combination with one or more active codes other than P2106 very well might.

Step 2

Consult the manual for the application being worked on for detailed information on the most likely causes of code P2106 on that particular application. As stated elsewhere, some applications are more sensitive to issues with the throttle control system that others, so investigate this possibility first if the manual recommends it.

Perform all diagnostic and testing procedures recommended by the manufacturer to either confirm or eliminate the throttle control system as the root cause of code P2106. Make repairs as required, clear the code, and operate the vehicle to see if the code returns.

Step 3

If the code and symptoms persist but the throttle control system is known to be good, and free of defects, failures, malfunctions, and/or intermittent electrical issues, consider the option of referring the vehicle to a repair shop for professional diagnosis and repair.

While it is possible for non-professional mechanics to diagnose and repair code P2106 successfully through a process of resolving all other codes in the order in which they were stored, this course of action is NOT recommended where complete and unambiguous fault data cannot be extracted from the OBD II system.

Additionally, bear in mind that due to the high number of possible root causes of code P2106, a non-professional mechanic would also require access to a complete set of reference data for the affected application, some of which is extremely difficult to obtain. Therefore, if Step 1 does not resolve the problem, the best option by far is to refer the application for professional diagnosis and repair.

Codes Related to P2106

  • P2104 – Relates to “Throttle Actuator Control System – Forced Idle”
  • P2105 – Relates to “Throttle Actuator Control System – Forced Engine Shutdown”

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