HELP>>>>I have a 98 TDI jetta 1.9 AHU motor. I have been plagued by a problem where my glow plug light immediately goes off when I turn the ignition key to start the car. Because the glow plugs don't come on the car is very sluggish with billows of smoke when it starts. Also, within a few seconds my glow plug light starts flashing with a steady "Check Engine" light on my display. I have changed out the relay and temporarily plugged in new temperature sending switch (connected a new switch to the plug leaving the old one still in the system) and the problem persists. When I disconnect the temperature sending module the glow plug light stays on. My rear brake lights are working, there's no water in my tank and ,worst of all, there's no error codes shown. I'm really puzzled, my mechanic says the only thing he can think of is to replace the car's computer but that's about $1,400 from the dealer. Any ideas would be greatly appreciated.