My truck has an intermittent cel that gives code 998. Originally we thought it was my map sensor and I sprayed it with wd40 to repel water and it seemed to fix the issue. However it keeps coming on. The truck runs fine most of the time with the code however sometimes it stalls. It’s hard to start. After going through all of this with the map sensor we’re starting to think it may be the trucks pcm. I know it’s common for the capacitors to leak in them but would the truck still run if it was bad? How do I go about testing it? Havent pulled it yet as I use the truck to get to school and practice

 

If you have codes in KOEO mode and you run a KOER test, then reader is telling you that you need to repair all KOEO codes before running or fixing KOER issues. This is IF your 998 code was in the KOER test when you got the 998. Code 998 causes the truck to go into LIMP mode and it will not run good. The computer knows you have KOEO issues.

 

I’ve been able to run the er tests before with codes in eo and not have it be in limp mode. I have code 553 and 118 I’m replacing the sensor for 118 so hopefully that goes away. Code 553 is probably hanging around tho because the truck has a smog delete. I’ll check the resistor to the tab/tad plugs maybe it’s loose

 

If your codes in KOEO are not severe the truck will not go into limp mode. If the truck has problems the computer deems as severe it will go into Limp mode to protect the truck. I show 553 and 118 as probably being in the KOEO mode or in Memory.