Check Engine light

It could be a sensor problem.My check engine lite comes on every day and come to the conclusion the warm weather plays a factor and climbing hills.When its cool out it does'nt come on.

 

Its been my experience that a MAF, O2 sensor, clogged crankcase filter, or PDF filter is the most common causes of a flickering check engine light. Clogged crankcase filters have been the most common cause for me.

 

Its a filter for the crankcase that ensures that the engine does not re-use oil-contaminated air. Look on both sides of the engine and you should see a housing for it. I have a 2013 detroit deisel and its on the left side but yours might be in a different location. The housing is usually square shaped and sealed with bolts and will also have a sensor connected to it. This is the same filter that occasionally triggers the "stop engine" light and well as the flickering "check engine". I believe they are suppose to be changed about every 6 months.

 

I meant DPF and its located inside the exhaust but you may not have one on a 1999.

 

All diesel engines have a crank case filter.