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EC-198 < DTC/CIRCUIT DIAGNOSIS > [VQ40DE] P0128 THERMOSTAT FUNCTION P0128 THERMOSTAT FUNCTION On Board Diagnosis Logic INFOID:0000000009483900 NOTE: If DTC P0128 is displayed with DTC P0300, P0301, P0302, P0303, P0304, P0305 or P0306, first perform the trouble diagnosis for DTC P0300, P0301, P0302, P0303, P0304, P0305, P0306. Refer to . Engine coolant temperature has not risen enough to open the thermostat even though the engine has run long enough. This is due to a leak in the seal or the thermostat being stuck open. DTC Confirmation Procedure INFOID:0000000009483901 NOTE: If DTC Confirmation Procedure has been previously conducted, always perform the following before conduct- ing the next test. 1. Turn ignition switch OFF and wait at least 10 seconds. 2. Turn ignition switch ON. 3. Turn ignition switch OFF and wait at least 10 seconds. WITH CONSULT TESTING CONDITION: • For best results, perform at ambient temperature of –10 °C (14°F) or higher. • For best results, perform at engine coolant temperature of –10 °C (14°F) to 58°C (136°F). • Before performing the following procedure, do not add fuel. If it is below 58 °C (136°F), go to following step. If it is above 58 °C (136°F), cool down the engine to less than 58°C (136°F). Then go to next steps. 6. Start engine and wait at idle for at least 10 minutes under the following conditions. CAUTION: Always drive vehicle at a safe speed. NOTE: If “COOLAN TEMP/S” increases to more than 71 °C (160°F) within 30 minutes, turn ignition switch OFF because the test result will be OK. 7. Check 1st trip DTC. WITH GST Follow the procedure “WITH CONSULT” above. Diagnosis Procedure INFOID:0000000009483902 1. CHECK ENGINE COOLANT TEMPERATURE SENSOR EC-199, "Component Inspection" OK or NG DTC No. Trouble diagnosis name DTC detecting condition Possible cause P0128 Thermostat function The engine coolant temperature does not • Thermostat VHCL SPEED SE More than 56 km/h (35MPH) |