Tip & How-To about Mercedes-Benz E-Class

Throttle Actuator Control - drive by wire

1.5) TAC - Throttle Actuator Control
What is it? Some vehicles have indirect throttle control "drive by wire". Instead of the accelerator pedal position being conveyed directly to the throttle plate by cable linkage, it is detected by an electrical sensor and this is fed to the ECU. The ECU in turn sets the position of the throttle plate appropriate to the sensed position using an electric motor. The throttle plate position is, in turn, checked by the throttle position sensor and this signal is sent to the ECU to confirm that the requested throttle plate setting and its recorded position are in agreement.

Where is it located? The first part of the TAC is located on the inner wing/fender and consists of rotary device to which the accelerator cable is attached; the degree of rotation (pedal depression) is detected electrically and this is signalled to the ECU. The second part of the TAC is located on the throttle body and acts on the throttle plate shaft.

Symptoms of a faulty TAC
Associated OBD2 error codes DTCs: P0120, P0124, P1516; P2102, P2103;P2111 - P2118

  • Sudden power loss/limp home: If the ECU detects any fault with the throttle actuator control directly or with the position feedback via the TPS it engages an immediate engine shut-down to either idle speed or limp-home speed.

How to fix? The TAC is part of complex systemand the failure of the TPS has to be eliminated first as a possible source of error. A simple electrical connection failure can also give rise to the shutdown so all associated connections should be checked to ensure that they are clean and bright to allow electrical continuity.

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Flash computer 2010 chevy equinox Abs, traction control, ck engine lights all come on. Vehicle goes into "safe" mode Drives at about 5 mph until I turn off & restart after 5 mins

Probably caused by the electronic throttle control . How many miles on the vehicle ? The gas pedal has position sensors that the PCM - engine computer uses to know how much to open the throttle plate .
Drive by Wire Function and diagnostics by Wells
What engine ?
The throttle actuator control (TAC) system is used to improve emissions, fuel economy, and driveability. The TAC system eliminates the mechanical link between the accelerator pedal and the throttle plate. The TAC system eliminates the need for a cruise control module and idle air control motor. The following is a list of TAC system components:
• The accelerator pedal assembly includes the following components:
- The accelerator pedal
- The accelerator pedal position (APP) sensor 1
- The APP sensor 2
• The throttle body assembly includes the following components:
- The throttle position (TP) sensor 1
- The TP sensor 2
- The throttle actuator motor
- The throttle plate
• The engine control module (ECM)

May 29, 2017 | Cars & Trucks

1 Answer

Buick lucerne starting disable throttle causes car not to crank

Drive by wire , electronic throttle control . What is it you would like to know Mr. Woods ? Can throttle cause car not to crank ? What year Buick ?
Throttle Actuator Control (TAC) System Description for the 4.6L engine or Throttle Actuator Control (TAC) System Description for the 3.8L engine.

The throttle actuator control (TAC) system delivers improved throttle response and greater reliability and eliminates the need for mechanical cable. The TAC system performs the following functions:
• Accelerator pedal position (APP) sensing
• Throttle positioning to meet driver and engine demands
• Throttle position sensing
• Internal diagnostics
• Cruise control functions
• Manage TAC electrical power consumption
The TAC system includes the following components:
• The APP sensors
• The throttle body assembly
• The powertrain control module (PCM)

Drive by Wire training

Jan 01, 2017 | Buick Cars & Trucks

4 Answers

It will not accelerate. I push on the gas and it won't go. I changed the oil a week ago and about a year ago i changed the fuel pump

Well an oil change is probably not the cause.
What IS it doing? You're telling me what it isn't doing...
Does the motor rev up?

Jun 10, 2015 | 2002 Chevrolet Tahoe

1 Answer

loss of power on dash and operates only at idle no matter how far i press on the gas pedal

Throttle Actuator Control (TAC) System Description
You have APP- accelerator pedal position sensors or one of the Throttle position sensors is going bad ! In the (TAC) system ! This is drive by wire or electronic throttle control . If you take it to the dealer or a ASE certified repair shop they can check the DTC'S - diagnostic trouble codes ! This is nothing for a DIYer to mess with ! This system can set 7 different DTC'S

Reduced Engine Power Mode When the PCM detects a condition with the TAC system, the PCM may enter a reduced engine power mode. Reduced engine power may cause one or more of the following conditions:
Acceleration limiting--The control module will continue to use the accelerator pedal for throttle control; however, the vehicle acceleration is limited.

Limited throttle mode--The control module will continue to use the accelerator pedal for throttle control; however, the maximum throttle opening is limited.

Throttle default mode--The control module will turn off the throttle actuator motor and the throttle will return to the spring loaded default position.

Forced idle mode--The control module will perform the following actions:

Limit engine speed to idle by positioning throttle position, or by controlling fuel and spark if throttle is turned off.

Ignore accelerator pedal input.

Engine shutdown mode--The control module will disable fuel and de-energize the throttle actuator.

Drive by Wire Function and Diagnostics by Wells

May 14, 2015 | 2004 Chevrolet Silverado 2500 Crew Cab

3 Answers

engine power loss message

You need to have it checked for DTC'S - diagnostic trouble codes , There is a problem with throttle actuator control (TAC) - electronic throttle control !
Throttle Actuator Control (TAC) Overview
The throttle actuator control (TAC) system uses vehicle electronics and components to calculate and control the position of the throttle blade. This eliminates the need for a mechanical cable attachment from the accelerator pedal to the throttle body. This system also performs the cruise control functions as well.
The TAC system components include, but are not limited to the following:
The accelerator pedal position (APP) sensors

The throttle body

The powertrain control module (PCM)
Each of these components interface together to ensure accurate calculations and control of the throttle position (TP).

Drive by Wire Function and Diagnostics by Wells

Mar 29, 2015 | Cars & Trucks

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