The 4 common causes of the Mazda and Ford EAC FAIL

Especially for the Mazda and Ford connoisseurs the 'EAC FAIL' is a well-known problem: with different models this error can appear on the display of the instrument panel. As soon as you search the internet for 'EAC', several stories appear. ACtronics has developed several solutions for this problem, because the underlying problem of the EAC fail can be different. In this article we will discuss this further!

What does 'EAC fail' mean?

The term EAC stands for Electronic Accelerator Control, which means that there is a problem with the transmission of the electronic signal from the accelerator pedal. This problem is mainly known in the following cars:

  • Mazda 2 DY (2003-2007)
  • Ford Fiësta 1.25 Duratec
  • Ford Fiësta 1.4 Duratec
  • Ford Fiësta 1.6 Duratec
  • Ford Fusion 1.25 Duratec
  • Ford Fusion 1.4 Duratec
  • Ford Fusion 1.6 Duratec

The throttle system of these cars is completely electronic. Operation is controlled by various sensors (such as potentiometers) and actuators. When you press the accelerator pedal, there is no steel cable that opens the valve of the throttle body. The throttle pedal has a Hall sensor that emits an electrical signal that is sent to the ECU. The ECU also receives a signal from the potentiometer on the throttle valve and then compares these two values. If necessary, the ECU will send a signal to the throttle valve's adjustment motor, with the result that the throttle valve opens further and the car will accelerate.

The connection between the engine and the accelerator pedal is purely electronic. The EAC FAIL will appear on the dashboard if the communication between the two is disturbed. The car will go into emergency mode, so that the car cannot go faster than 30 kilometres per hour, no matter how deep the driver presses the accelerator pedal.

What are the symptoms of an EAC error code?

Contrary to several other dashboard reports, the EAC fail can in some cases be detected prematurely: a (too) high idle speed with a warm engine is such a recognizable symptom that the car will probably get the EAC error code.

What causes an EAC fault code?

The EAC fail can have different causes. The car model (type) can also be of great importance. Therefore we will describe the common causes of the EAC fault code below:

Cause 1: a defective ECU

With the Ford Fiësta V and Fusion produced before June 30, 2002, the ECU (also known to Ford experts as the 'PCM' or powertrain control module) is often the cause of the EAC fail. This is the Siemens SIM 22 PCM that often generates the error codes P2138 in combination with P2122, P2123 or P2127.


Fortunately, ACtronics can help with this problem, because remanufacture is possible. Note the following: after revision of this part, the keys and the instrument panel need to be reprogrammed. Also here ACtronics can help. At least, when both components are sent in to us with the ECU.


Cause 2: A defective throttle body

A common cause of the EAC FAIL in the Ford Fiesta V and Ford Fusion is a defective throttle body (and specifically the throttle position sensor). To be 100% sure that the throttle body is the cause of the malfunction, it is best to study the live data. If it turns out that the throttle body is indeed defective, then the component will have to be removed. To do this, remove the throttle body from the inlet manifold, remove the inlet air hose, unscrew the torx screws, disconnect the connector and look for the serial number and the product date. If the serial number is less than 400 000, the throttle body is very likely to be defective. ACtronics can help by performing a remanufacture of the throttle body. Use the search bar on our website to find the OE number.

Cause 3: wiring

Another cause of the defect could be the wiring. To determine if this is the case, all connectors between the throttle pedal, the PCM (ECU) and the throttle body must be cleaned. This can cause deposits or slight corrosion on the pins. If the error code has disappeared after cleaning the instrument panel, this means that the problem has been solved.

Cause 4: A defective accelerator pedal

If the accelerator pedal is depressed, but the engine speed does not change at all, there is also a real chance that a defective accelerator pedal is the problem. The signal that is normally sent from the accelerator pedal to the ECU is also visible in the live data of some diagnostic testers. In this way, the operation can easily be checked.

Overview of related error codes

When diagnosing the EAC FAIL, there are a number of error codes that often occur in the event of a defective throttle body as well as in the event of a defective one. These are the following error codes:

Throttle body error codes

  • P0120 – TPS "A" circuit fault
  • P0122 – Throttle position sensor switch / switch (TPS) A Circuit Low Input
  • P0123 – Throttle position control pedal / switch (TPS) A Circuit High Input
  • P0220 – Throttle position sensor / switching circuit throttle lever B malfunction
  • P0222 – Gas pedal position switch / sensor B Low input circuit
  • P0223 – Throttle position sensor / switch pedal switch B Circuit high input
  • P2135 – Throttle position sensor switch / switch A / B Voltage relation
  • P2119 – Throttle actuator Regulation Throttle body / performance
  • Check the wiring and connectors of this error code again.

  • P2176 – Throttle control system Control - In rest position. Not learned
  • P2100 – Throttle drive control circuit - Circuit opener (TACM)
  • See the circuit between the throttle body motor and the PCM.

ECU error codes

  • P2107 – Throttle drive control module processor
  • P0641 – Reference voltage sensor “A”, interruption
  • P0642 – Sensor reference voltage "A" signal too weak
  • P0643 – Sensor reference voltage "A" signal too high
  • P0651 – Reference voltage sensor "B" interruption
  • P0652 – Sensor reference voltage "B" signal too weak
  • P0653 – Sensor reference voltage "B" signal too high