Mazda 323/MX-3/626/MX-6/Millenia/Protégé 1990-1998 and Ford Probe 1993-1997

Engine Control Unit (ECU)

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OPERATION



The Engine Control Unit (ECU) does exactly what its name suggests; it controls the engine. By reading input signals from various sensors, it interprets the signal, then makes adjustments by controlling various output devices, such as the fuel injectors or an EGR solenoid. In this manner, the ECU can monitor and control the air/fuel ratio, ignition timing, idle speed, engine temperature, etc. By doing so, the ECU is able to run the engine at an optimal level at all times, giving fuel economy, power and stringent emission control.

REMOVAL AND INSTALLATION



See Figure 1


WARNING
Whenever working on or around the ECU, ensure that the negative battery cable has been disconnected. The ECU is a sensitive micro-computer and susceptible to electrical shock damage.

  1. Disconnect the negative battery cable.
  2.  



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Fig. Fig. 1: The ECU is mounted under the center console. Typical ECU mounting shown

  1. On all models except the 1993-98 626/MX-6/Probe models, proceed as follows:
    1. If necessary, remove the driver side under dash cover.
    2.  
    3. Remove the passenger and driver side cover walls from the center console unit. On 1995-98 Protege, this includes the front center console cover as well.
    4.  
    5. If applicable, detach the rear heater ducts behind the side covers to gain access to the ECU electrical connectors.
    6.  

  2.  
  3. On 1993-98 626/MX-6/Probe models, remove the center console trim plate around the gear select lever.
  4.  
  5. Remove the ECU mounting bolts/nuts and detach the ECU electrical connectors.
  6.  
  7. Installation is the reverse of the removal procedure.
  8.  

 
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