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Home >> Jeep >> 1996 >> Cherokee Classic, Part Time, Automatic >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> Engine Controls - Tests W/Codes - 4.0L >> Diagnostic Trouble Code (DTC) Identification >> Test TC-128A - Closed Loop Temperature Not Reached
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Test TC-128A - Closed Loop Temperature Not Reached

NOTE: For connector terminal identification, refer to CONNECTOR IDENTIFICATION . For wiring diagram, see WIRING DIAGRAMS article in this section.
NOTE: The following test is invalid if thermostat is stuck open.
  1. Check thermostat operation. Replace thermostat if necessary and perform TEST VER-2A . if thermostat is operating correctly, go to next step.
  2. CLOSED LOOP TEMP NOT REACHED DTC sets if engine temperature does not reach more than 18°F (-7.7°C) within 10 minutes of engine start. Possible causes are: defective thermostat, defective Engine Coolant Temperature (ECT) sensor, extremely cold ambient temperature, defective PCM, defective connector terminals or connector wires. Go to next step.
  3. Using scan tool temperature probe, check engine temperature. Run engine until engine temperature reaches more than 80°F (26.6°C). Turn ignition off and go to next step.
  4. Disconnect ECT sensor connector. Inspect connector and terminals for damage. Repair connector and terminals as necessary and perform TEST VER-2A . If connector and terminal are okay, go to next step.
  5. Using an external ohmmeter, check resistance across ECT sensor. If resistance is 11,000 ohms or more, replace ECT sensor and perform TEST VER-2A. If resistance is less than 11,000 ohms, go to next step.
  6. Disconnect Powertrain Control Module (PCM) connectors. Inspect PCM connectors and terminals for damage. Repair connectors and terminals as necessary and perform TEST VER-2A . If connectors and terminals are okay, replace PCM and perform TEST VER-2A.
NOTE: A break in test sequence occurs at this point. Sequence skips from TEST TC-128A to TEST TC-132A. No tests have been omitted.
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