Hi everyone, I have owned a 2003 350z for several years now and it has been giving me this issue. The car had aftermarket led tail lights and every time the headlights were on the car would lose power and cruise control did not work. With headlights off everything was normal. I always assumed this was related to the LED tail lights, as many have had the same issue because of this...

I now would like to sell the car, but I need to fix this first. I bought stock 03 tail lights installed them and it still has the problem. All other lights are stock. The car is a 2003 6MT touring 350z with some mods including HKS grounding kit, intake, plenum spacer, exhaust. This clearly seems to be an issue with the ECM causing it to go into Limp mode only when the lights are on. Very strange, has anyone had a similar issue? what fixed it?

 

Do you know if any of the non LED bulbs were replaced with aftermarket LEDs? Things like the front parking lights, signal/indicator bulbs, license plate lights? I would double check the wiring harness area on the front headlights and rear signal lamps to see if there were any past modifications, like resistor kit addons.

Good Luck!

 

Check the rear brake lamps/bulbs. I had an issue where the bulbs were bad and causing the Z (my 03 track at the time) to go into limp mode. ECM takes the voltage drop across the bulb... When they go bad, it sees a voltage that is out of spec and goes into limp mode. Such a weird design

-NT

 

As NissanTracker mentioned, if your rear brake lamps are out "for any reason" many modern vehicles will put the car into some form of limp mode (Note: The lamps could still be functioning, but if the BCM "thinks" they are out because of resistance/voltage changes outside what it's programmed to expect, it will still treat it as a dead lamp). I just didn't know the 350Z had this safety feature as well, or at least this is the first time I've heard of it.

For example, my brother has a 2016 4Runner w/ automatic trans, while doing some accessory electrical work, the rear brake lamp fuse was removed and then accidentally placed in a NULL/Blank fuse slot ( there's a lot of blanks for some reason on that car), thus disabling the rear brake lights completely and causing the BCM to think there was a major failure.

Because the vehicle is an Automatic, the ECU/BCM would not allow you to put it in Drive or Reverse, the transmission was essentially locked in park because the rear brake lamps were not working. Note that there is a manual override mechanism in place for Automatic Transmissions (at least in the 4Runner's case), but it's not a well known procedure and depending on the vehicle make/model/year could require you to remove interior paneling around the center console shift lever.

I suspect a 350Z with a Manual Transmission attempts to do something similar by using limp mode. I'm not sure how I feel about this level of user lockout by vehicle manufacturers.

 

What is bad, is Nissan technicians will go through their typical troubleshooting steps to find the culprit... but it could be a significant amount of time before they actually find something related to brake lamps/bulbs. It is not a typical reason for a performance related issue.

For example, on my manual 03 track... the dealership tried to feed me a 800 dollar diagnostics bill after spending days figuring out why it was going into limp mode. After getting a lawyer involved, they fed it to Nissan corp.

 

Thanks for the responses I still have yet to find the source of the problem. What is interesting is front parking lights/side marker lights light up when I press my brakes and the headlights are off...

Also when my headlights are on all 3 lights light up instead of just the two tail lights.

 

Sounds like you have some wiring issues.. retrace all the wires..start from the rear to the front.. and id replace any aftermarket lighting with OEM to eliminate the possibility .

 

coilovers, wheels/tires, weight reduction.