usually indicates a problem has been detected some-
where within the fuel system. The DRBIII scan tool
is the best method for communicating with the MSA
and PCM to diagnose faults within the system.
DESCRIPTION AND OPERATION
POWERTRAIN CONTROL MODULE (PCM)
The MSA controller is mounted under the left side
rear seat (Fig. 1). The Powertrain Control Module
(PCM) is mounted in the engine compartment. (Fig.
2).
The MSA Controller is a pre–programmed, digital
computer. It will either directly operate or partially
regulate the:
•
Speed Control
•
Speed Control lamp
•
Fuel Timing Solenoid
•
Check Engine Light
•
Glow Plug Relay
•
Glow Plugs
•
Glow Plug Lamp
•
ASD Relay
•
Air Conditioning
•
Tachometer
•
Electric Vacuum Modulator (EVM)
The MSA can adapt its programming to meet
changing operating conditions.
The MSA receives input signals from various
switches and sensors. Based on these inputs, the
MSA regulates various engine and vehicle operations
through different system components. These compo-
nents are referred to as MSA Outputs. The sensors
and switches that provide inputs to the MSA are con-
sidered MSA Inputs.
MSA Inputs are:
•
Air Conditioning Selection
•
Theft Alarm
•
ASD Relay
•
Control Sleeve Position Sensor
•
Fuel Temperature Sensor
•
Mass Air Flow Sensor
•
Accelerator Pedal Position Sensor
•
Engine Coolant Temperature Sensor
•
Low Idle Position Switch
•
5 Volt Supply
•
Vehicle Speed Sensor
•
Engine Speed/Crank Position Sensor (rpm)
•
Needle Movement Sensor
•
Starter Signal
•
Brake Switch
•
Speed Control Switch
•
Power Ground
•
Ignition (key) Switch Sense
MSA Outputs:
After inputs are received by the MSA and PCM,
certain sensors, switches and components are con-
trolled or regulated by the MSA and PCM. These are
considered MSA Outputs. These outputs are for:
•
A/C Clutch Relay (for A/C clutch operation)
•
Speed Control Lamp
•
ASD Relay
•
5 Volts Supply
•
Fuel Quantity Actuator
•
Fuel Timing Solenoid
•
Fuel Shutdown Solenoid
•
Glow Plug Lamp
•
Check Engine Lamp (“On/Off” signal)
Fig. 1 MSA Controller Location
Fig. 2 PCM Location
ZG
FUEL SYSTEM—2.5L DIESEL ENGINE
14 - 27
GENERAL INFORMATION (Continued)
Summary of Contents for 1997 Grand Cherokee
Page 6: ...FASTENER IDENTIFICATION 4 INTRODUCTION ZG GENERAL INFORMATION Continued ...
Page 9: ...METRIC CONVERSION ZG INTRODUCTION 7 GENERAL INFORMATION Continued ...
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Page 1684: ...TORQUE 9 86 5 2L ENGINE ZG SPECIFICATIONS Continued ...
Page 1689: ...Fig 3 Oil Lubrication System ZG 5 9L ENGINE 9 91 DESCRIPTION AND OPERATION Continued ...
Page 1723: ...DIAGNOSIS AND TESTING SERVICE DIAGNOSIS DIESEL PERFORMANCE ZG ENGINE 9 3 ...
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