Wednesday, August 30, 2006

P0118 and P1128 codes on 2000 Audi with 1.8L engine


Hard starting after engine has warmed up including poor acceleration and rough idle. P0118 code (engine coolant temperature circuit defect) and P1128 (long term fuel trim system lean) were taken after scanning. Do I change the coolant sensor?

Basic Concept:

Whenever code P0118 appears and your thermostat is checked OK, replace the coolant sensor because it is a common problem on this model. What is happening is, the coolant sensor is stuck in flood mode causing the hard or long cranks because there is too much fuel. The other code is caused by a contaminated mass sensor that can be serviced or replaced.

Repair Strategy:

Replace the coolant sensor first to fix the first code and before servicing the mass sensor, make sure to check for vacuum leak using ATS tips or have it smoked by a garage. On some extreme case, the vacuum leak is caused by an intake manifold leak that requires a top end job. This is why you need it smoked if the 2nd code keeps coming back. When resetting the codes, remove the battery cables and touch them together for at least 15 seconds.


Anonymous Anonymous said...

I just ran into this code on a 1.8T Passat, I assume same analysis. I also noticed that the coolant on my vehicle is below the 'low level' mark on the overflow tank. Since the check engine light has been going on and off now for a couple of weeks I'm guessing that there is a good chance adding coolant will fix the problem. If not, I'm sure it's the sensor

3:43 PM  

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