P1284 Buick Air Fuel Ratio Sensor 1 Rich Shift Monitoring Bank 2

P1285 Buick Cylinder head over temp sensed

Possible causes
  • Low engine coolant level.
  • Base engine concerns.
  • Engine cooling system concerns.
  • CHT sensor concern.
    • Tech description
    On some applications when this fault occurs the Engine Temperature warning indicator will illuminate and/or force the temperature gauge to the full H (hot) zone. The warning indicator can be triggered by either grounding the engine temperature warning circuit when wired to the PCM, or by sending a PCM network message to the instrument cluster.
    Symptoms
    – Engine Light ON (or Service Engine Soon Warning Light)
    P1285 Buick Description

    Indicates an engine overheat condition was sensed by the Cylinder Head Temperature (CHT) sensor.

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