Chrysler Front Wheel Drive Cars 6-CYL 1988-1995 Repair Information

Engine Control Unit

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OPERATION



See Figures 1, 2 and 3

The main computers, which controls the fuel injection system on all vehicles covered by this information, are referred to as the Powertrain Control Module (PCM) on all non-Premier and Monaco vehicles. On 1988-90 and early 1991 Premier and Monaco vehicles, it is called the Engine Control Unit (ECU), whereas on the late 1991 and all 1992 Premier and Monaco models (with the Direct Ignition System), it is known as the Single-Board Engine Controller (SBEC). The engine computer (PCM, ECU or SBEC) is a digital computer containing a microprocessor. The engine computer receives input signals from various switches and sensors that are referred to as engine computer inputs. Based on these inputs, the engine computer adjusts various engine and vehicle operations through devices referred to as engine computer outputs.



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Fig. Fig. 1: The Powertrain Control Module (PCM) and the Single-Board Engine Controller (SBEC) are the same component-except early Premier and Monaco



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Fig. Fig. 2: The Engine Control Unit (ECU) is also mounted in the same position as the PCM or SBEC is, behind the battery and on the inner left fender wall



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Fig. Fig. 3: The multi-port fuel injection related components-except early Premier and Monaco

The engine computer inputs are as follows:



Air conditioning controls
 
Battery voltage
 
Brake switch
 
Engine coolant temperature sensor
 
Distributor pick-up
 
Manifold Absolute Pressure (MAP) sensor
 
Oxygen sensor
 
Speed control system controls
 
Throttle position sensor
 
Park/Neutral switch (automatic transaxle)
 
Vehicle speed sensor
 

The engine computer outputs:



Air conditioning clutch relay
 
Alternator field
 
Idle Air Control Motor (IACM)
 
Auto Shutdown (ASD) and fuel pump relays
 
Canister purge solenoid
 
Malfunction indicator lamp
 
Data link connector
 
Electric EGR Transducer (EET)
 
Fuel injectors
 
Ignition coil
 
Torque converter clutch solenoid
 
Radiator fan relay
 
Speed control solenoids
 
Tachometer output
 

Based on inputs it receives, the engine computer adjusts fuel injector pulse width, idle speed, ignition spark advance, ignition coil dwell and canister purge operation. The engine computer regulates the cooling fan, air conditioning and speed control systems. The engine computer changes the alternator charge rate by adjusting the generator field.

The distributor pick-up signal is sent to the engine computer. If the engine computer does not receive a distributor signal within approximately one second of engine cranking, the ASD relay and fuel pump relay are deactivated. When these relays are deactivated, power is shut off to the fuel injector, ignition coil, oxygen sensor heating element and fuel pump.

The engine computer contains a voltage converter that changes battery voltage to a regulated 8.0 volts. The 8.0 volts power the distributor pick-up and vehicle speed sensor. The engine computer also provides a 5.0 volt supply for the coolant temperature sensor, manifold absolute pressure sensor and throttle position sensor.

REMOVAL & INSTALLATION



See Figures 4 through 10

  1. Remove the air cleaner duct or air cleaner assembly from the engine.
  2.  
  3. Remove the battery from the vehicle as described in Engine Electrical .
  4.  
  5. Remove the engine computer mounting screws.
  6.  
  7. Remove the 60-way connector from the engine computer. Remove the engine computer from the vehicle.
  8.  



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Fig. Fig. 4: The PCM location on Dynasty, New Yorker, Imperial and Fifth Ave. models



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Fig. Fig. 5: The PCM location on Daytona and LeBaron coupe and convertible models

To install:
  1. Plug the 60-way connector into the engine computer.
  2.  
  3. Install the PCM on the inside left front fender. Install and tighten the mounting screws.
  4.  
  5. Install the battery into the vehicle.
  6.  
  7. Install the air cleaner duct or air cleaner assembly.
  8.  



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Fig. Fig. 6: To remove the PCM/SBEC, first disconnect the air duct hose from the computer housing



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Fig. Fig. 7: After removing the battery/tray, loosen the center bolt from the 60-way harness connector



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Fig. Fig. 8: Pull the 60-way connector out of the PCM/SBEC and make sure all of the connector holes are clean



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Fig. Fig. 9: Loosen and remove the mounting screws from the PCM/SBEC ...



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Fig. Fig. 10: ... then pull the PCM/SBEC out of the engine bay

 
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