Hello all,
I recently obtained a 2003 G35 M6 (built Dec 2002) with a series of issues.I got it cheaply and am working out the bugs. Most problems seemed to be old gaskets, broken clips to the Variable timing, which also needed some cleaning, airbag reset, and O2 sensors that were close to dead upstream. And it needed some better grounding.

With that, all errors are gone except one: Can Bus connection error. I checked the harness just a little bit, I don't see anything obviously wrong. However, I don't know which wire is the ground on the harness, so I am not guaranteed there is something wrong there. I did run a separate ground to the ECU just in the hopes that might fix it, but no difference.

Car starts and drives. Car idles low. No check engine light, nothing else on the dash lit up. However scanning the ECU I see the model number 23710-AC405. Calling the infiniti dealer, they tell me the part number that comes up for my VIN is 23710-AM701. Referencing that number, I believe this is also called aMEC31-930 B1
Using the online parts for infiniti, it says the one in the car is not compatible as an alternative for the car.

So, I'm just checking here if there is an ECU compatibility list somewhere? Looking at the junkyards, when you put in the car and VIN, they come up with variations of the number the dealer gave. It makes me think that's what happened, is the junkyard replacement this person put in was close so it starts but is not capable of talking correctly to the other parts of the car the right way. Because the junkyards show at least 5 different model numbers they say match.

With all that said, does anyone know? And, does anyone have a suggestion for a place to get one with the right number?

I found one place, but I don't recognize them from anywhere, anyone dealt with them?

https://www.fs1inc.com/23710-am703-2...31-930-b1.html

They have the exact match. and program it for the VIN .

With a new ECM, do I then simply use the NIssan datascan II to to reprogram the car keys? I presume the immobilizer will stop the car from starting if I don't.

Thanks for any thoughts.

 

Ok, probably what happened is somewhere along the lines the ECM in the car failed and someone replaced it with another one. This isn't a problem though because there's quite a few different ECM's that could technically work in the car, as long as it was properly programmed to the BCM to accept the keys and initialize NATS then it will work (which sounds like everything is working and the car will drive).

As for the CANBUS code, it's a bunch of various components all networked together, if ANY of the computers is not connected to CANBUS you will get the same generic U1000 code. It can be a real pain in the *** to find out which one is the issue, especially if you have the early model ECM that's not tunable.

You have NDS2 for windows right? You can use it to partially diagnose which computer is having issues because you won't be able to connect to it.

The ECM, BCM, instrument cluster, VDC/TCS/ABS, IPDM fuse box, and the steering angle sensor all connect to the CANBUS high/low wires. (2006-2007 also the RAS computer).

One way to test is to make sure the wires are intact to EACH of the computers. Since the high/low CANBUS is also accessible at the OBD2 data link connector you can use a digital multimeter and a length of wire to see if it's a continuous circuit, it's a bit tedious though, this will let you know for sure that the wire isn't broken somewhere.

FSM section LAN - Local Area Network has good pinouts for each of the harnesses.

 

Also, does your 2003 have one electric fan, one mechanical fan. Or does it have dual electric fans?

 

Interesting that you say different ones will work. That's different from what the dealer says, but maybe that's the official line vs otherwise us in the field testing it out. But my research seems to back this up, you can't just use any other model number because, as you said, the BCM and others' won't accept it. And, although I might be misunderstanding, the NATS/keys are simply keyed to the ECU, so as long as the keys are reprogrammed, that doesn't really tell me much except they reprogrammed the keys. So....not sure what to think of that. My understanding is that the BCN and all other systems are expecting the matching VIN, but that might also be a misunderstanding, so a connectivity test, although a good idea and one I will also do, wouldn't fix this mismatch. I suppose an easy test will be to program the ECM with the right VIN and see what happens.

But, more importantly, the pinouts are one thing, but where are all those items? BCM is easy it's right near the ECM, but for things like the dash, do I have to pull it out to test the wiring? steering angle sensor I presume means I have to take the steering wheel off?

Thanks.

 

ECM get programmed to accept a specific BCM, BCM gets programmed to accept a specific key. The BCM is a lot more chassis specific because it handles everything related to the chassis of the vehicle. Basically every button inside from the windows and door locks, lights, etc. There were some changes in the coupe or sedan with the addition of things like heated seats and such so you really do need the EXACT BCM for the car.

ECM is a little bit looser since it's just handling the function of the ENGINE. There were technically 4 major different ECM's but each one had a few revisions. 3 of those ECM's had different harness plugs so those were pretty cut and dried. Of the final variation there was essentially the rev-up and the non-rev-up version. Of those 4 variations of the ECM there was the 6MT and the 5AT version, for a total of 8 actual different ECM's if you wanted to just plug-n-play (after doing the match pair programming to accept the BCM) one from a wrecking yard.

Then there are the ECM's available for the 350Z which also work as long as it's got the right harness and was for the correct transmission type.

Now the kicker is these ECM's are PROGRAMMABLE using Up-rev (and NDS2 for PC to a degree), so TECHNICALLY you could use almost any ECM as long as it plugs in and just upload the software to it since you can just change all the variables to match what you're actually doing with it (with UpRev, NDS2 doesn't allow that kind of programming but you can take 350Z ECM and use it if it is the correct harness and transmission).

The BCM not so much, you can basically just turn on/off NATS and program a new key. The rest is pretty set in stone, a BCM from a sedan was designed to handle windows/locks on 4 doors and can't be swapped to a coupe. Can't add or subtract functionality for chassis options like heated seats and such.

Steering angle sensor wiring is accessible directly under the airbag, you can leave the steering wheel bolted to the steering column.

Check out the FSM section LAN - Local Area Network. It goes over the entire system and has locations for stuff, it's pretty basic overall. You could start by just disconnecting the battery, unplugging a component, plug the battery back in, see if any NEW CANBUS codes show up. Then narrow down which component isn't working by looking for one that DOES NOT add a new code.

 

Ah, that's a good idea too! I will find some time.

Thank you for the suggestions.