BMW Cars 1999-06

Engine Control Module (ECM)

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Description & Operation




NOTE
The terms Engine Control Module (ECM), Powertrain Control Module (PCM) and Digital Motor Electronics (DME) control unit are used interchangeably and refer to the vehicle's computer control module, regardless of the terminology used.

The Engine Control Module (ECM), also referred to as the Powertrain Control Module (PCM) or Digital Motor Electronics (DME) control unit, uses a variety of input sensors which send electrical signals which are interpreted by the ECM to control the fuel delivery, ignition timing and idle speed of the engine.

These input signals include the following:



Mass Air Flow (MAF) sensor (OBD II)
 
Airflow meter (OBD I)
 
Throttle Position (TP) sensor
 
Air temperature sensor
 
Engine Coolant Temperature (ECT) sensor
 
Crankshaft speed sensor
 
Camshaft Position (CMP) sensor
 
If equipped, knock sensors
 
Pre Catalyst Oxygen sensor (OBD I)
 
Pre Catalyst and Post Catalyst Heated Oxygen sensor (OBD II)
 

The engine's idle speed, idle mixture, and ignition timing are not adjustable and are controlled by the ECM. The fuel mixture is controlled by the ECM by changing the opening time (pulse width) of the fuel injectors.



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Fig. The basic components of the OBD I engine management system

Removal & Installation



E30 Models

NOTE
If possible, replace the ECM after the engine has reached normal operating temperature otherwise poor driveability may occur. When the battery is dis­connected, the control unit's adaptive memory will be lost. Once the engine is restarted, the system will readapt after about 10-15 minutes of driving.

  1. Turn the ignition switch OFF .
  2.  
  3. Open the glove compartment and remove the pins from the straps so the door drops down.
  4.  
  5. Remove the upper trim piece to access the Engine Control Module (ECM) unit.
  6.  
  7. Push the plug retainer back and remove the plug. Remove the 4 bolts and remove the ECM unit.
  8.  

To install:

  1. Install the ECM unit and the 4 bolts.
  2.  
  3. Install the plug onto the ECM unit and snap the retainer into place.
  4.  
  5. Replace the trim and the glove compartment door.
  6.  

E36 Models

NOTE
If possible, replace the ECM after the engine has reached normal operating temperature otherwise poor driveability may occur. When the battery is dis­connected, the control unit's adaptive memory will be lost. Once the engine is restarted, the system will readapt after about 10-15 minutes of driving.

  1. Turn the ignition switch OFF .
  2.  
  3. Disconnect the negative battery cable and wait approximately 90 seconds.
  4.  
  5. The ECM is mounted behind a panel on the right side of the firewall. Remove the 3 press-in plugs holding the shield over the ECM cover. Then, remove large threaded buttons securing the insulation and remove.
  6.  
  7. Remove the housing cover fasteners
  8.  
  9. Pivot the top of the housing outward and lift up to remove
  10.  
  11. Grasp the electrical connector locking bracket and lift it out until it releases.
  12.  
  13. Once the bracket is released, carefully pull outward to detach the electrical connector
  14.  
  15. Unhook the heel of the electrical connector and carefully lift it away from the control unit
  16.  
  17. Remove the relay mounting bracket, the retaining screws and slide the control unit out of the housing. If there are 2 control units, the upper control unit is for the automatic transmission and the lower is the ECM.
  18.  

To install:

  1. Install the ECM unit and connect the plug. Lock the connector down.
  2.  
  3. Install both covers. Check the routing of the wiring harness.
  4.  
  5. The remainder of installation is the reverse of the removal procedure.
  6.  



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Fig. To remove the control module, first remove the large threaded buttons securing the insulation



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Fig. Next, remove the housing cover fasteners



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Fig. Pivot the top of the housing outward and then lift up to remove



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Fig. Grasp the electrical connector locking bracket and lift it out to release



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Fig. Once the bracket is released, carefully pull to release the electrical connector



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Fig. Unhook the heel of the electrical connector and carefully lift it off the control unit



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Fig. Remove the relay mounting bracket, the retaining screws, then slide the control unit out of the housing

 
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