P2101 – Throttle actuator control (TAC) motor – range/performance problem

By Randy Worner (Contact Me)
Last Updated 2016-07-05
ASE/ACA World Class Technician

Table of Contents

1. What Does Code P2101 Mean?
2. What are the common causes of code P2101?
3. What are the symptoms of code P2101?
4. How do you troubleshoot code P2101?
5. Codes Related to P2101
6. Get Help with P2101

What Does Code P2101 Mean?

The engine computer (PCM) controls the Throttle Actuator Control (TAC) system. This includes the motors that move the throttle plate. The PCM looks at the throttle position sensor on the driver’s pedal to determine the driver’s intent and then calculates the appropriate throttle response. The PCM accomplishes this by pulsing a voltage signal for up to 2 TAC motors. This moves the throttle plate to the desired position.

The main component of this system is the throttle body, which is located between the intake manifold and the air filter. It will have up to 2 motors that move the throttle plate and one or more throttle position sensors to let the PCM know where the throttle plate is located at all times. Typically, when the command to the motors to move the plate does not correspond to the voltage signal sent back by the throttle position sensors (TPS), code P2101 can be set.

What are the common causes of code P2101?

• Dirty/obstructed throttle plates/throttle body – very common
• Faulty Throttle Actuator Control (TAC) module/Throttle Body (Very Common – especially if it was cleaned by someone not familiar with the correct cleaning procedure for the particular vehicle or if the TAC/ETC system relearn procedure was not carried out correctly)
• Failed PCM – unlikely

What are the symptoms of code P2101?

• Malfunction Indicator Light “ON”
• Electronic Throttle Control Indicator “On”
• No throttle response – engine will only idle

How do you troubleshoot code P2101?

First things first: make sure you are not fighting yourself from the get go. Take a look and see if there are any technical service bulletins (TSB) for your particular vehicle. There may be a known fix put out by the manufacturer and can save you from wasting time and money.

Next, note if there are any other diagnostic fault codes. Insure that the battery is fully charged and not weak. Weak batteries can cause the current at the electronic throttle motors to go up. Higher than normal under hood temperatures have been known to contribute to this as well. Marginal/weak batteries have been known to set intermittent P2101 fault codes. Diagnose current faults first, in the order in which they are stored. Look for any engine performance related issues, and diagnose those next. Misdiagnosis has been known to occur if a technician diagnoses this code before any engine performance / vehicle communication related system codes have been thoroughly diagnosed and dismissed. Also misdiagnosis occurs when this code is diagnosed when it is a stored code while other codes are active.

Next, locate the Throttle Actuator Control (TAC) system on your particular vehicle. Typically, it is located between the intake manifold and the air filter. Once located, remove the tube that runs from the TAC system to the air filter. Once removed, visually inspect the throttle plates to see if they are clean and free of debris. With the ignition switch off, you should be able to slowly rotate the throttle plate by pushing in on it. It should slowly rotate to the wide open position. If there is a considerable amount of sludge behind the plate, clean it while you are there, taking care not to damage the throttle body by pushing in very quickly or by doing so while the ignition switch is in the “Run” position (unless instructed to do so by the vehicle manufacturer). Clean behind the plate area by spraying a rag with carburetor cleaner and wiping it out. DO NOT SPRAY ANYTHING INTO THE INTAKE! This only causes all the sludge to travel into the cylinders, possible coating the spark plugs and worse. Once completed, reattach the hose from the TAC system to the air filter housing.

Clear the diagnostic trouble codes from memory, and see if this code returns. If it does not, then the sludge buildup was most likely your problem.

If the code does return, with a scan tool monitor Actual Throttle Plate Position versus Desired Throttle Plate Position. They should be within 2 degrees of each other. If this test passes, check your scan tool’s functional tests. See if some type of “Throttle Follower Test” is available. If so, remove the air filter to TAC system hose once again and watch the throttle plates move as you perform this test. If either test fails, a TAC system / Electronic Throttle Control / throttle body replacement is indicated.

If all tests have passed so far, and you continue to get a P2101 code, this would most likely indicate a failed Throttle Body Assembly, although a failed PCM could not be ruled out until the TAC/ETC system had been replaced. Anytime the throttle body is removed or replaced, the PCM will need to go through a idle system relearn procedure in order to relearn throttle plate position. Also, if a PCM must be replaced, it must be programmed in order it work on that particular vehicle. At this point it is probably wise to consult with a trained automotive diagnostician.

Codes Related to P2101

• P2110 – Throttle actuator control (TAC) system – forced limited rpm mode – Usually P2110 goes along with the P2101, as some of the same issues that set P2101 can set the P2110.
• P2101 is typically related to mechanical issues while the P2110 is almost strictly electrical / motor issues.

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