From Ross-Tech Wiki

17663/P1255 - Engine Coolant Temperature Circuit (G62): Short to Ground

Possible Symptoms

  • Difficulties with starting a cold engine.
    • Diesel: an indication is extreme long time burning time of the glow indication light.
  • Starting the engine when engine is warmish or warm, idle rpm immediately is 1200 - 3000 rpm.
  • RPM at idle is irregular.
  • With all engine temperatures seldom idle rpm will vary between 900 - 1000 rpm.
  • With engine warm (90 °C) the engine temperature suddenly drops (70 °C) and slowly comes back to 90 °C.
  • Bad acceleration during warming up.

Possible Causes

  • Wiring and/or connections faulty
  • Engine Coolant Temperature Sensor (G62) faulty

Possible Solutions

  • Check wiring and connections
  • Check / Replace Engine Coolant Temperature Sensor (G62)

Special Notes

  • In MY 1995-2002 (?) in Europe at VW-cars the G2/G62 had the bad reputation of breaking down often. The default G2/G62 is black and all replacements are green.