Mazda Trucks 1994-1998 Repair Guide

Powertrain Control Module (PCM)/Electronic Control Module (ECM)

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OPERATION



The PCM/ECM performs many functions on your car. The module accepts information from various engine sensors and computes the required fuel flow rate necessary to maintain the correct amount of air/fuel ratio throughout the entire engine operational range.

Based on the information that is received and programmed into the PCM's memory, the PCM generates output signals to control relays, actuators and solenoids. The PCM also sends out a command to the fuel injectors that meters the appropriate quantity of fuel. The module automatically senses and compensates for any changes in altitude when driving your vehicle.

REMOVAL & INSTALLATION



See Figure 1



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Fig. Fig. 1: Typical PCM module

B Series Pick-up and Navajo Models

See Figures 2 and 3

The module is mounted under the hood on the firewall. On 1994 models, it is mounted low on the firewall, near the left-hand fender (drivers side). On 1995-98 models, it is mounted high on the firewall offset to the right-hand side of center.



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Fig. Fig. 2: Exploded view of the firewall PCM mounting for 1994 models



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Fig. Fig. 3: Exploded view of the firewall PCM mounting for 1995-98 models

  1. Disconnect the negative battery cable.
  2.  
  3. Disengage the wiring harness connector from the PCM by loosening the connector retaining bolt, then pulling the connector from the module.
  4.  
  5. Remove the two nuts and the PCM cover.
  6.  
  7. Remove the PCM from the bracket by pulling the unit outward.
  8.  

To install:
  1. Install the PCM in the mounting bracket.
  2.  
  3. Install the PCM cover and tighten the two nuts.
  4.  
  5. Attach the wiring harness connector to the module, then tighten the connector retaining bolt.
  6.  
  7. Connect the negative battery cable.
  8.  

MPV Models

See Figures 4 and 5

The PCM/ECM is mounted in the vehicle's interior, under the dashboard on the right (passenger) side.

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the right side scuff plate and right front side trim.
  4.  
  5. Lift up the front mat.
  6.  
  7. Remove the protector cover.
  8.  
  9. Unplug the wiring harness connector from the control module.
  10.  
  11. Loosen the mounting fasteners and remove the PCM/ECM from the vehicle.
  12.  



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Fig. Fig. 4: Remove the protector cover



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Fig. Fig. 5: Location of the control module on the front right side of the interior

To install:
  1. Place the PCM into the vehicle in correct position.
  2.  
  3. Install the mounting fasteners and tighten to 70-95 inch lbs. (8-10 Nm).
  4.  
  5. Plug the wiring harness connector into the PCM/ECM.
  6.  
  7. Install the protector cover and place the mat back in proper position.
  8.  
  9. Install the right front side trim and the right side scuff plate.
  10.  
  11. Connect the negative battery cable.
  12.  

 
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