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1.0 INTRODUCTION The procedures contained in this manual include specifications, instructions, and graphics needed to Please follow the recommendations below when choosing your diagnostic path. 1. First make sure the DRBIII t is communicating with the appropriate modules; ie., if the DRBIII t displays a ‘‘No Response’’ condition, you must 2. Read DTC’s (diagnostic trouble codes) with the DRBIII t. 3. If no DTC’s are present, identify the customer complaint. 4. Once the DTC or customer complaint is identi- fied, locate the matching test in the Table of All component location views are in Section 8.0. All connector pinouts are in Section 9.0. All system An * placed before the symptom description indi- cated a customer complaint. When repairs are required, refer to the appropri- ate service manual for the proper removal and Diagnostic procedures change every year. New diagnostic systems may be added; carryover sys- After using this book, if you have any comments or recommendations, please fill out the form at the 1.1 SYSTEM COVERAGE This diagnostic procedures manual covers 2001 Grand Cherokee Jeep vehicles with a JTEC Engine 1.2 SIX-STEP TROUBLESHOOTING Diagnosis of the Powertrain Control Module (PCM) is done in six basic steps: • verification of complaint • verification of any related symptoms • symptom analysis • problem isolation • repair of isolated problem • verification of proper operation 2.0 IDENTIFICATION OF The Powertrain Control Module (PCM) monitors and controls: • fuel system • ignition system • charging system • speed control system • automatic transmission 3.0 SYSTEM DESCRIPTION AND 3.1 GENERAL DESCRIPTION The JTEC engine and automatic transmission systems have the latest in technical advances. The 3.2 FUNCTIONAL OPERATION 3.2.1 FUEL CONTROL The PCM controls the air/fuel ratio of the engine by varying fuel injector on time. Mass air flow is Different fuel calculation strategies are used de- pendent on the operational state of the engine. 1 GENERAL INFORMATION |