So today is the 3rd time this has happend to me and Im stumped. My 99 5.2 D will show a check engine light every so often but when I go to run a scan tool on it while the light is still on it shows no codes and the light will shut off on its own after a few start ups and not come back on for a lil. Anyone have any idea what this could be?

 

gremlins!

 

Yea for real got me all sorts of confused, I cant figure out why it would be showing the light with no codes?

 

Ive seen and heard of things like this before...It could be a bunch of different things I am sure.
I once had an Isuzu Vehicross, that after I did my own CAI would throw the CEL randomly...come to find out when I actuall caught it it was just the engine telling me there was to much air. LoL

 

My truck Is bone stock only problem I have is an exhaust leak at the muffler and at the tailpipe that I throw a flowmaster 40 and put a new tailpipe on it next week. I wouldnt think It would throw an engine code though since its after the cat.. Other than that I know of nothing else going wrong on it.

 

Hmm...have you tried reseting the pcm? Mabey it was an old one that was fixed and the pcm just hasn't gotten rid of it?

 

Hav you tried this method of retrieving the codes? It works on the '99 Dakotas.

Depress the trip reset and trip/odometer switches, and, while holding them, turn the ignition to ON/RUN, and wait about 5 seconds. This sends the car through a short self-test sequence that lights all segments of the odometer and shift selector read-out (where applicable). It will then display the stored error codes.

 

Hmm.. Nope never heard of that worth a try atleast I will check it in the morning when I get off work to see if it works.

 

That is only the instrument cluster diagnostic tool. The CEL is different to the cluster diagnostic tool.

You are dealing with a shadow code, which in turn means a code that is being tripped, however not hard enough to be a hard code and be set into the system. What I want you to do is give the truck a small tune up. This means new Champion Copper spark plugs (yes the cheap ones) gap them at .040 and install. Go get some better gas. Then take the TB off and clean tha thing out!

After this reset the PCM and see how she runs.

 

Right on... a full tune up was done in march but its cheap enough, I will redo it again to see if it comes up with any luck on that. If nothing I will pull TB and clean it, Do I have to pull the whole intake on it or is it seperate on it?