2003 1.8L Passat engine service alarm

[loucarrozza]

Service engine is displayed. Dealer claims that thermostat, temperature sensor and connector are faulty. However, my thermostat appears to be working and my temperature indicator as well. A day after I left dealer the light went out but its on again and every thing they mentioned seems to be working? Any ideas? I suspect a loose or defective connector.

[MikeCStig]

Some cars have maintainance schedules programmed into the engine computer. The alert you're getting may be about your car being due for maintenance checks according to one of those schedules. It doesn't mean that there's something wrong with the indicated parts, it just means that it's time to check those parts. They may be fine, they may need adjustment or replacement.

[harleyguy]

Yes some of the vw's have a service interval (can't remember now if it's the same as check engine light or not) but the fact that it was off for a while then came back would point elsewhere. Did they say anything about pulling codes. These things are notorious for coolant sensor problems. But I can't say I have ever changed the plug.

[MikeCStig]

I had that with my golf this past winter. My check engine light came on and that was the code that came up. The water pump and the coolant level were fine so I changed the sensor, reset the computer, and the problem was solved. That might be it too, get the code checked to be sure. Some garages will check codes for free.

[loucarrozza]

Originally Posted by MikeCStig

Some cars have maintainance schedules programmed into the engine computer. The alert you're getting may be about your car being due for maintenance checks according to one of those schedules. It doesn't mean that there's something wrong with the indicated parts, it just means that it's time to check those parts. They may be fine, they may need adjustment or replacement.

THANKS FOR YOUR INPUT. YESTERDAY, I WENT TO AUTOZONE AND THEY CHECKED THE CAUSE FOR ENGINE SERVICE LIGHT. THEY GOT A po118 CODE. IT INDICATED A POSSIBLE TEMPERATURE SENSOR OR CONNECTOR FAILURE. ITS POSSIBLE THAT THE CONNECTOR IS JUST LOOSE BUT HOW DIFFICULT IS IT TO REPLACE THE SENSOR AND/OR THE CONNECTOR CABLE?

[MikeCStig]

Mine wasn't too difficult, but it may be a bit different on a passat, I'm not sure. Start by disconnecting the battery. Of course, you'll want to do this with a Cold engine as your hands will be around a lot of hot stuff. With mine, the engine cover had to come off so I could see what I was doing and so I could get my hand in there. It was right near the end of the lower radiator hose that is attached to the engine. There's a c-clip that has to come out, then you can just pull the sensor out. Make sure the old seal (o-ring) comes out too, sometimes they stick in place instead of just coming out with the sensor (mine did). Anyway, before you put the new one in, make sure the new seal is on it just right... this is critical, if it's not seated properly it will leak coolant. Put the new sensor in place (ideally with a new plug) put the new c-clip in, hook the battery back up, start the engine and let it run until it's fully warmed up, then cross your fingers and check to make sure there aren't any leaks.
Again, the exact location of your temperature sensor may be different from mine, but the procedure should be about the same.