Could the recent ECU i just had put in not be an exact match? would having an incorrect ecm flash codes that would not apply? just thinkin out loud over here

 

TBI, right? I suppose it's possible the ECM for a 2.5 could run the 3.9....... but it shouldn't run very well.... Rather lean, I should think.

 

Right its TBI and it runs very well. So why am i getting a code that points to a radiator fan low speed relay circuit when the truck has a thermal clutch fan? i don't get it

 

In the results for both my codes, Ralph, it has two asterisks after which says that the check engine light would come on and stay on...My check engine light stays Off....WTH is going on? What are all my truck problems some kind of weird challenge

 

Either you're misreading the blinks (possible!) or your ECU is, well, a bit confuzzled.

Can you video the blink sequence so someone else can try counting the blinks?

You SHOULD end with a 55 (End Of Codes) in any case; if you didn't, then 100% the codes were misread.

RwP

 

guess i could send a video but i counted twice. i got the 12 then the 17 then the 35 and lastly the 55.

 

Oh yeah; i drove for bout 20mins and the gauge needle never went even close to the middle. the needle was barely inside the operating range marks. thermostat? The coolant was hot but couldn't say if it was hot enough; and the heater was working so idk.
thanks

 

Gauge and ECU uses different sensors on our trucks. Might be thermostat.

As to "hot" ... well, thermostat should be a 195F unless you've swapped in a 180F.

RwP

 

thanks; i'll get it replaced in a couple days and report back. appreciate the help!

 

First off, how many miles on the 3.9? Problems on a 250,000 engine will be different than the ones on a 50,000 mile engine. The low operating temperature lead to one of three problems. Most likely is a failed or too cool thermostat. Second would be a worn timing chain set. Lastly, I've seen burnt valves cause an engine to have weird temperature issues.