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Home >> Suzuki >> 2001 >> XL-7 Limited >> Repair and Diagnosis >> External Pages >> Different car >> Section 17 (Engine Controls - Self-Diagnostics) >> Diagnostic Tests >> DTC P0128: Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature) >> Diagnosis & Repair Procedure

Diagnosis & Repair Procedure

WARNING: This page is about a different car, the 2002 Suzuki Grand Vitara. However, it is still accessible from the selected car via links, so may be relevant.
  1. If engine system check has been performed, go to next step. If engine system check has not been performed, see and perform A4: ENGINE SYSTEM CHECK  under SYSTEM TESTS and go to next step.
  2. Inspect thermostat. Make sure that air bleed valve of thermostat is not clogged. Check valve seat for foreign matters which would prevent valve from seating tight. Check thermostat seal and "O" ring for breakage, deterioration or any other damage. Immerse thermostat in water, and heat water gradually. Check that valve starts to open at 186.4-193.6 °F (86-90 °C). If valve operation is as specified, go to next step. If not, thermostat is faulty.
  3. With ignition switch OFF, install scan tool and disconnect ECT sensor coupler. With ignition switch ON, check engine coolant temperature displayed on scan tool. When shorting ECT connector terminals C10-1 and C10-3 with service wire, temperature should be 401°F (205°C). When ECT connector terminals C10-1 and C10-3 are open, temperature should be -40°F (-40°C). If results are as specified, go to next step. If results are out of specification, check for faulty Orange/Black and or Grey/Yellow wire. If OK, substitute known-good ECM (PCM) and recheck.
  4. Check ECT sensor referring to ENGINE COOLANT TEMPERATURE SENSOR in SYSTEM & COMPONENT TESTING article. If check result is as specified, substitute known-good ECM (PCM) and recheck. If check result is not at specified, ECT sensor is faulty.
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