Hello. 2004 suburban 5.3, flex, Z with the KNP RPO code. Here is what thay code reads.
KNP COOLING SYSTEM,TRANSMISSION,HEAVY DUTY

My question is, I read that this code means that I have an EXTERNAL trans cooler. Is that correct? In front of the Radiator/Condenser. There IS a radiator there. Roughly 11" long.

But I know my trans fluid runs through the main radiator with the Engine Coolant. I replaced that rad a couple years ago and tranny lines and coolant lines went to it.

Is that radiator up front something else? Maybe a oil cooler? It measures about 11" across. 2 lines coming from the bottom of the radiator.

I want to replace it because I was in an accident and one of the metal lines has a slight bend in it. No leaks tho.

I know its not coolant radiator, it'* not the Power Steering rad. Theoretically it'* not tranny fluid, That just leaves a oil cooler... am I missing something? Or did I just over think this lol.

No other RPO codes list heavy duty oil coolers or anything. The truck does have the Z82 railering package, ZW7 smooth ride,

I'm wondering if there was another line that was in series with the engine radiator/trans cooler side and it was removed. ???

Or, the previous owner bypassed the external cooler due to trans not getting up to temp because of winter temps. I've seen this before.

Its possible. I think the rad does heat up. I can check on that after work. The truck has been in the family since 2006 or 2005. Its possible the last owner messed with it but I'm not sure.

I can probably find the answer if I unbolt one of the lines and look whether the fluid is tranny fluid or oil.

The output of the radiator feeds the input of the external cooler and it feeds the trans input.

I'd follow the lines and look for what carfixer007 said ^^^^^^^ before loosening a line on a damaged unit. A little bit of torqueing around might finish it off.

Can you post a picture of the damage?

https://m.imgur.com/a/CKTUTeA
Sure. Heres an imgur link. Right in the middle of the line you can see a slight kink. The bumper folded in and a piece of it was pressed on that line. Nothing leaks by the radiators. The accident was in August. And at least 5k miles ago. I just straignted the mounts and slapped a new bumper on and called it a day. Gonna cat eye swap at some point.

Thank you. This makes sense.

This?:



If so, and if it isn't leaking, I wouldn't worry about it. That bend is very slight.