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ACCESSING DIAGNOSTIC TROUBLE CODES A stored Diagnostic Trouble Code (DTC) can be dis- played by cycling the ignition key On-Off-On-Off-On They can also be displayed through the use of the Diagnostic Readout Box (DRB) scan tool. The DRB EXAMPLES: flashes 2 more times, a flashing Diagnostic Trouble • If the lamp flashes 1 time, pauses and flashes 7 more times, a flashing Diagnostic Trouble Code After any stored DTC information has been observed, the display will end with a flashing DTC ERASING TROUBLE CODES After the problem has been repaired, use the DRB scan tool to erase a DTC. Refer to the appropriate Powertrain Diagnostic Procedures service manual for DRB SCAN TOOL For operation of the DRB scan tool, refer to the appropriate Powertrain Diagnostic Procedures ser- WATER PUMP TESTS LOOSE IMPELLER—4.0L and 4.7L NOTE: Due to the design of the 4.0L and 4.7L DO NOT WASTE reusable coolant. If solution is clean, drain coolant into a clean container for reuse. (1) Drain coolant until the first row of cores is vis- ible in the radiator. (2) Leaving the radiator cap off, start the engine radiator fill neck, raise engine rpm to 2000 RPM. (4) If there is no flow or very little flow visable, replace the water pump. INSPECTING FOR INLET RESTRICTIONS Inadequate heater performance may be caused by a metal casting restriction in the heater hose inlet. DO NOT WASTE reusable coolant. If solution is clean, drain the coolant into a clean container for WARNING: DO NOT LOOSEN THE RADIATOR DRAINCOCK WITH THE SYSTEM HOT AND UNDER (1) Drain sufficient coolant from the radiator to decrease the level below the heater hose inlet. On (2) Remove the heater hose. other restrictions. NOTE: On 4.0L engines remove the pump from the Fig. 18 Data Link Connector Location 1 – HEADLAMP SWITCH BRAKE PEDAL) 7 - 10 COOLING SYSTEM WJ DIAGNOSIS AND TESTING (Continued) |