Hey all, new to the forum. Not new to the G35. Upon searching multiple threads I haven’t been able to find a similar thread with a concrete answer for what exactly is going on with my G. Hoping to find one here,

Here’s some of the backstory/facts...

Just purchased an 03 g35 coupe AT, 260km (161 miles), has a cold air intake and borla cat back exhaust. Also the stock headunit has been replaced, headlights appear to be factory HID. No other mods that I’ve noticed (I got the car yesterday).

I know the battery was no good upon arrival so I replaced it with a new Nissan battery I had, car starts up fine with no CEL’s. However when I turn off the car the front parking lights (small circular orange lights at the lowest part of the headlight housing) immediately turn on and the driver side rad fan remain on after the key is set to the OFF position as well as after the key has been removed. This continues regardless of how long I wait and is the same outcome with the car hot or cold. It only stops when I remove the battery terminal. Now I am familiar with the AUTO Function on the light selector stock and I insured it was set to the OFF position. When the car is running ON or key is In ACC I am able to shut off parking lights via its control however the fan still runs (I’ll have to confirm it continues to run). Has anyone heard of this issue or expected it?

After I remove the battery terminal, wait, and put the battery terminal back on the fan/lights immediately turn back on and I can hear a relay click in the IPDM so I’m guessing I have a corroded/stuck relay? However is it possible that a fan relay can cause the lights to come on as well? I know high and low beam relays are in the IPDM as well. Could it be a bad common ground for the IPDM? (Location E22 termination ground I think) - I have a schematic for all the grounds so I’ll probably clean them all up.

Now if all that wasn’t confusing enough. Yesterday, while I was trying to diagnose I noticed that when I shut the drivers door a little harder it turned off the fan and lights. I assumed it was a feature of the coupe, (to run the fan to cool the engine after its been turned off and shut off the fan when the door is shut) But today shutting the door has zero effect on the lights or fan. They still run continuously. So I am not sure if that is related to the problem or just a coincidence...

Sorry for the long intro, just want to provide as much info as I can. Going to start tearing into it tomorrow morning with a meter in hand but just wanted to see if anyone has any guidance before I spend the time on diag.

Thanks again in advance.

Welcome to NICO!

I've re-titled your post to better reflect the topic, which should garner more responses.

Anyway, it sounds to me like you may have an electrical short somewhere. I hate to say it, but you may have to have the dealership run diagnostics on it to see if they can narrow down the problem.

Thank you for the welcome and I appreciate the title rename. Dealer is always an option, pricey as it may be. I bought the car as a side side project to my 300zx so I’m not rushing it off to the dealer just yet. I’m not new to electrical gremlins (I previously worked at AMG Canada and the Germans invented electrical gremlins in my opinion). I pulled relays this morning and began pulling relays to try and narrow down my search, removing 3 fan relays, high and low beam relays and a/c relay didn’t effect my parking lights at all. Only one small click in the IPDM when the terminal goes back on and I assume it’s the ecm relay just turning on. So kinda ruling out a bad IPDM once I check it’s grounds.
**side note when I applied the battery terminal this morning the fan didn’t automatically turn on however the parking lights still did. I agree there must be some sort of short...looks like I may be stuck testing point to point on all the wires in said system for resistance (grounded wire).

Also, when I put on the battery terminal this morning there is a relay click from the driver side area by the firewall, I see nothing there but master cylinder, is there another relay box under the cowling or am I hearing a relay click from inside the kick panel of the car? (I assume there are relays in there as well.

Thanks

Cool beans. Looks like you're on the right track.

As for other relays, I'm not all too well versed in your vehicle, but can offer an option for you. Here at NICO, we have Factory Service Manuals available free to members. Here's the direct link for your car: Index of /FSM/G35/Coupe/2003 Hopefully you'll be able to locate any relays you didn't discover on your own.

And when you get a chance, post some pictures of your car.

FSMs are GREAT!!
Thanks so much

When turning off the car the fan should not continue to work. Slamming the door and the lights/fan stopping seem to indicate a short or loose connector.

You also mentioned when turning the car on you heard a relay and thought it might be stuck, if it were stuck I would not think it would click at all.

You are correct, I do believe it’s a short. Tested every removable relay in the IPDM, all are fine. Knowing the tail lamp relay is actually internal and attached to the board in the IPDM I replaced the IPDM with a model from an 03 rwd sedan. (I know coupe and sedan aren’t the same units so Wipers ran non stop which I expected it to do so) but the fans and lights still did the same thing with the new IPDM so ruling out the IPDM being the culprit. I tested bcm and IPDM for power and ground with no faults and checked the red/blue CAN wires from the bcm to the IPDM for resistance to indicate a short but no fault either.
Everything on the lighting schematic I checked, it all checked out fine. I read the FSM back to front and stumbled on A tidbit of info that Infiniti should have really elaborated on but on PG-23 of the 03 Coupe FSM they write:

Function of Detecting Ignition Relay Malfunction AKS003I3
● When contact point of integrated ignition relay is stuck and cannot be turned OFF, IPDM E/R turns ON tail and parking lamps for 10 minutes to indicate IPDM E/R malfunction.
NOTE:
When the ignition switch is turned ON, the tail lamp is OFF.

^^^Thats it, no further explanation. After it’s just info on the Active Auto Test. There are some brief diagnostic check lists to follow that but it’s clearly reliant on using the Consult II.

So chasing the light issue actually isn’t an issue, it’s supposed to do that when there is a fault with anything to do with the IPDM circuit. In this case it’s the cooling fans that are triggering it. Signal begins at 2 locations; coolant temp probe at RH rear of engine OR when the A/C is activated via climate control. This signal goes to the ECM (a/c signal goes to bcm then ecm) and then out to the IPDM (as there is 2 stages for fan speed) and then to the fan(S).

So there are some more things I can check for sure to narrow down my search. I feel it’s the ECM unfortunately, I have no CEL/Body or ABS codes when the car is running or driving, it behaves like a really healthy car. However when I turn it off and remove the battery, then re-install and scan I get a C1132 code, no warning lights on the dash but the code is there.
C1132 is either:
-faulty ECM
-faulty CAN communication line
-faulty ABS module

I’d rule out the abs module because the abs works and triggers no lights. (I live in Canada and the ABS gets used this time of year lol)

The common unit between my fan issue and the code is the ECM. Would be wise to check resistance of the wiring before I replace it though.

Waiting for a nice day or may move my 300zx to another heated storage location to free up space in the garage and go in depth to test the harness/ecm. -However for the mean time I’m running a battery kill switch into the car to simply disconnect the battery once the car it turned off. I planned to do this anyways as this car will rarely get driven and the “sleep mode” /clock will drain the battery in a week or so. I Removed the 12v cigarette lighter on the driver side and actually found a kill switch that fits perfectly in that hole so it’s a pretty damn clean install. I’ll post pics.

I’m not giving up on this electrical issue and I’ll post all my findings here, unfortunately I’m in Canada and it’s too damn cold to be working outside.

You are doing great following through in troubleshooting.

From a troubleshooting perspective if relay 1 is stuck "ON" and the other 2 are "OFF" then the fans would be running on a low speed, otherwise it would take all 3 relays to be stuck "ON" or receiving a signal to be "ON" for the fans to be on high.

Based on the above to see if relay 1 has a problem simply swap it with relay 2 as that would be a "OFF / ON / OFF" condition which should not turn the fans on low. Obviously if the fans are staying on high then this would be a waste of time. Fan relay operation is page EC-474 of the FSM.

If the relays are not the problem at all then they would have to be receiving a signal from the ECM and I don't believe any of the other components which control the fan turning on (via triggers through the ECM) would be enable with the ignition off, thus, ECM would probably be the problem itself unless there is a short or wiring issue on the CAN itself between the ECM and IPDM as you noted above.