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DTC P0128: THERMOSTAT MALFUNCTION Subaru Outback BH

Testing & Diagnostics ~180 words
  1. Perform basic diagnostic procedure. See «BASIC DIAGNOSTIC PROCEDURE»(ref-63535-S26517940312001020900000) . If vehicle has been idling for an extended period or operated with engine partly submerged in water, clear codes and allow engine temperature to stabilize. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-63535-S26931138132001020900000) . Road test vehicle. Using scan tool, retrieve DTCs. If DTCs P0125, P0301, P0302, P0303, P0304, P0305 and P0306 are all displayed at the same time, go to next step. If DTCs P0125, P0301, P0302, P0303, P0304, P0305 and P0306 are displayed individually (not all at the same time), repair those codes first.
  2. Check coolant level and antifreeze solution mixture ratio. Drain and refill coolant as required. If coolant level and solution mixture are correct, start engine and check cooling fan operation. If cooling fan runs continuously for more than 3 minutes with engine at idle, repair cooling fan circuit. See WIRING DIAGRAMS article. If cooling fan does not run continuously for more than 3 minutes with engine at idle, replace thermostat. Clear memory and perform verification procedure. See «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-63535-S26931138132001020900000) and «VERIFICATION PROCEDURE»(ref-63535-S38101445392001020900000) .

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