2007 infiniti g35 coupe AT, not sure if its the ipdm or ecu or the relay for the ecu im assuming its the ipdm since there was some corrosion on the ecu relay and the plug in part to the ipdm (i have no cover on the ipdm so rain is able to run down onto the ipdm), but basically i got this code p0603 never got it before n while looking up the code and looking on prodemand ive come to those 3 assumptions i checked my grounds and my positive battery cable terminal incase any of the 4 links were broken and nothing, as stated never got the code before ive already replaced the ipdm once 10 months prior to the one in the car now cause the fuel pump relay kept blowing, ive already put a different relay in for the ecu going to do a ecu reset and then drive the car to see if that did anything as a temporary fix but if someone knew further n could help as i have inspection that was due months ago that would help just got back from college so not able to spend thousands

 

P0603 is the backup power for the ECM, it's supplied directly from the fusible link, not the IPDM. You probably blew fuse 34 in the fusible link. That's the one that supplies backup power to the ECM.

This has nothing to do with the IPDM, nothing to do with the ECM relay. These fuses are easy to blow if you're working on the electrical system with the battery still connected. Be sure to disconnect the battery before unplugging ANYTHING on these cars.

You need to get a cover installed securely onto the IPDM or you're going to be chasing other electrical gremlins.

 

ended up replacing the fusible link as suggested by you along with the relay just incase, car starts n runs fine shifting has improved idles perfectly havnt done a full road test as i only zipped round the neighborhood going 40 foh about 2 half miles in total driving distance n no code so ill keep watch but assume the problem is fixed

 

For the future, you don't need to replace the entire fusible link, just the individual fuses. Fuse 34 is the ECM backup power.

 

mhm gotcha see i thought B 100 on the link was what you were talking about but i just replaced the correct fuse, fuse wasnt blown but showed ah lil sign of burn had extra 15s in the car so all good now, i appreciate the help and the diagram car still runs just as good and still no code

 

Awesome, hopefully that fixed your problem.

 

update, the code came back so any idea on what the next possible cause could be

 

I'd start by cleaning up the grounds, ECM ground and battery negative ground wire (both ends of the cable).

These computers are super picky about stuff like that, have you had ANY trouble starting the car? Even weird things like "I turned the key this one time and it wouldn't start but the second time it did" or "sometimes my windshield wipers act up" can help narrow down the culprit.

 

i pulled the fuse out from the wipers so they dont move regardless, and no the car has started up perfectly every time the key has turned, only difference in addition to the code is my car went into limp mode i guess thats what it is, i tried to drive it and the accelerator stopped working my revs would still go up no further than 2k but speed stayed at 10 im pretty sure my negative terminal is clean, the cars been sitting in one spot since december with the negative cable disconnected so with all the leaves n dirt from what i saw when i lifted the hood it could be dirty but the ecm ground where is that, is that the ground on the driver side right below the air intake next to the spark plugs ?

 

No that's probably the ground for the headers on that side, or the one on the front of the wheel well is for the driver side headlights. The ECM ground is under the glove box.