Engine running codes, what is it?

[Vanner1993]

I have codes 21, 41 and 33. I know 100% for sure that my ECT has no issue or wiring issue. Code 33 I have no idea what to look for and code 41 is my latest issue. I can not pass inspection, and the truck is running very rich. Is this my o2 sensor? It's a pain to get out to look at but what would cause these 3 codes?

 

[RyanL]

The engine coolant temperature sensor (2-wire) controls the A/F ratio along with intake air temperature sensor and oxygen temperature sensor. You did these checks with the engine warmed up, right? I have to ask because there was a guy in another thread that was having issues and I assumed he did the test right. You will get that one code 21 if the engine is too cold. If it's warmed up and you're getting that code it's a bad coolant temperature sensor. They're cheap enough, but if your o2 sensor hasn't been changed in a while, it might be time for that anyway (I usually do them when I change out the plugs). Anyway, it sounds like you may have a couple of problems. I wish that I could be of more help for your EGR issue (the '88 i used to have didn't have an EGR nor does the '89 I have now), but from what I can gather it sounds like your vacuum actuator isn't working right (it should have a little vacuum valve which opens and closes). If you're lucky it's just a leaking vaccum hose, but it should be easy enough to test the actuator. I think there may also be some sort of fitting which gets all gummed up too with these EGR systems. Hopefully someone more knowledgeable will chime in.

 

[Psychopete]

21 - if this was from KOER, engine wasn't warmed up when you did the KOER test.

41 - can be an o2 sensor, but from what I have seen, in most cases the oxygen sensor really is sensing too much oxygen in the exhaust. That could be anything from a misfire to a vacuum leak.

33 - sounds related to your code 41 as EGR function is vacuum dependent.

(pretty much a summary of what RyanL said lol)