Re: Jeep 2.7 crd grand cherokee 2004
Welcome to the garage.
Never tried it myself, but i don´t think the fault codes will reset by disconnecting the battery. You could try it though. Otherwise only by using a scanner.
Indeed better to reset the codes first and check if they come back. There are codes which can be set, but without the "check engine" light coming on. So you could have had most of these codes for some time already and only one of them could have tripped the "check engine" light.
Strange that you also have a knock sensor code, because i don´t think the 2.7 crd has knock sensors.
So reset them first and let us know what you get thereafter.
And regarding service manual, do a search on google. There are free service manuals or at some places you have to pay a bit to download. The 2004 manual i have shows some wiring schematics for diesel as well, but the engine is not in there. I found the diesel suplement somewhere else, but don´t remember anymore where it was.