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Home >> Suzuki >> 2002 >> XL-7 Plus >> Repair and Diagnosis >> External Pages >> Different car >> Section 6 (Engine Controls - Self-Diagnostics) >> Diagnostic Tests >> DTC P0128: Engine Coolant Temperature Sensor Below Thermostat Regulating Temperature >> Diagnostic Procedure
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Diagnostic Procedure

WARNING: This page is about a different car, the 2002 Isuzu Trooper. However, it is still accessible from the selected car via links, so may be relevant.
  1. Perform ON-BOARD DIAGNOSTIC II SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM. After performing OBD-II system check, go to next step.
  2. Visually check air duct and water pipe for splits, kinks, proper connections and routing. If problem is found, repair as necessary. After repair is complete, see VERIFYING VEHICLE REPAIR  under SELF-DIAGNOSTIC SYSTEM. If no problem was found, go to next step.
  3. Inspect air filter for restrictions. If problem is found, repair as necessary. After repair is complete, see VERIFYING VEHICLE REPAIR  under SELF-DIAGNOSTIC SYSTEM. If air filter is okay, go to next step.
  4. Remove and inspect thermostat for proper operation. Replace thermostat if necessary. If no problem was found, go to next step.
  5. Turn ignition on. Review and record FAILURE RECORDS data on scan tool. Operate vehicle within FAILURE RECORDS conditions. On scan tool, monitor DTC information. If scan tool indicates DTC P0128 FAILED THIS IGNITION, leave ignition on and go to next step. If scan tool display is not as specified, go to DIAGNOSTIC AIDS .
  6. Using scan tool, observe ENG COOL TEMP parameter. If parameter is less than 282°F (139°C), go to DIAGNOSTIC AIDS . If parameter is 282°F (139°C) or more, go to next step.
  7. Turn ignition off. Disconnect PCM Blue 80-pin harness connector E-21. PCM is located at right rear of engine compartment. Check for short to ground or to sensor ground circuit in Blue/Red wire between PCM and ECT sensor. See WIRING DIAGRAMS article. If problem is found, repair as necessary. After repair is complete, see VERIFYING VEHICLE REPAIR  under SELF-DIAGNOSTIC SYSTEM. If no problem was found, go to next step.
  8. Replace and reprogram PCM. See POWERTRAIN CONTROL MODULE REPLACEMENT  under POWERTRAIN CONTROL MODULE. Use scan tool to clear DTC and verify repair.
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