fault code 4
 

I have a 90 300E w/150k mi. Recently "check engine" light has came on and wouldn't go away. I checked the fault code at the diagnostic box w/led light. The light flashed 4 times. The fault code#4 is related to Air flow sensor, I believe. Anybody have any idea what does this code mean. The car is still runing fine even with the "check engine" light came on.

DTC for your . . . .
 

'90, 300E (KE) with 124.026/030/090 chassis with 103.983/940 KE is:

#4: Potentiometer voltage illogical

Is your idle speed OK? Usually a bad air flow sensor position indicator will affect your idle speed. (high idle) What about your fuel economy?

If your car is running fine, retrieve the code again, then erase it by pressing the button 6-8 seconds. See if the trouble code pops up again after driving your car. If so test or replace the part.

Good luck and welcome to the board! :p

Thanks for all the reply. The car is running find except the idle is kindda low about ~500-600 but it been like way before the "check engint" light came on. I reset the code as you told me to and the "check engine" light hasn't come back on yet. It has been couple of days already.