Alright so I learned yesterday that my aftermarket taillights were drawing a different amount of current than stocks. Seeing as how our cars have a sensor tied into the brake light that throttles down the engine when it senses light is activated, the car’s acceleration and overall performance was very inconsistent. I don’t have any idea how I missed this problem…

On some days and times, throttle would be very responsive, and on other days it would not be as responsive and would hesitate. I have had those tails on so long, even before I learned a lot about the Z, so I had gotten used to it I guess. So I take them off last night and WHAM, everything performs better. Braking is more smooth ( I guess cause now the Z throttles down correctly) acceleration is consistent and smoother, idle is smoother, startup and shutdown is smoother, etc. So besides the brake/throttle down issue, I assume everything was affected by this voltage issue at least a little. I don’t think mine was affected as much as others were because I obviously didn’t see anything when I installed them, but when I took them off, the difference was very noticeable.

Anyways my question is, if the car was dyno tuned with a reflash while I had these tails on, would the car need to be retuned now? How would this problem affect the tune, if at all? How much difference would a retune make, if any? And finally, would simply doing an ECU pedal reset help the ECU ‘relearn’ and adjust for this change?

TIA fellas.

 

I personally wouldn't bother with a re-tune if it were my car, it is cost prohibitive. Maybe you can get the A/F verified at the next local dyno day and make a decision based on those results.

 

you're thinking of that sensor in the wrong way.

It only works when the BRAKE light is activated not the tail light therefore there shouldn't be a change in acceleration unless you are trying to accelerate with your foot on the brake. If you're having issues with your tune it's not the tail lights. You can easily pull the brake light fuse and see. It doesn't NOTHING to acceleration. It's only there for the abc/traction control stuff. It won't allow you to hold the brake and the accelerator.

 

+1

It's usually pulled by those who want to warm the tires up thoroughly at the track.

 

Right, i hear what you guys are saying but your missing something somewhere along the way. This problem has been proven with quite a few others having the same throttle down problem, including a big thread by Vas 33 which i will go retrieve here in a min.

Also, i understand that this sensor is tied to the brake light, however the tails also light up when brake pedal is depressed, not just the 3rd brake light, so they are prob tied to the same relay if thats what you mean. That being said, the discovery was made that with these tails sending the wrong current, the ECU is thinking that you are braking when your not, so it is trying to throttle down at certain points during acceleration.

Now, it could just be that with these tails causing a voltage issue, the electrical system via ECU is causing wrong voltage levels throughout the system and therefore hindered performance, but others have determined that the most likely culprit is the brake sensor/throttle down.

Like your saying, guys pull the fuse so that they can burn out, because pressing both pedals wont work BECAUSE the ECU will counter throttle. Thats what is happening here. THe ecu is counter throttling thinking that the brake light is on, when in fact it is just miss voltage from the tails confusing the ECU while your brake pedal isnt even depressed, and your trying to accelerate.

Also, you misunderstand my problem. There is nothing wrong with the tune, its the taillights that were the problem. My worry is that if the car was tuned while these tails were causing voltage havoc in the ECU, then the car might be mis-tuned to what it should be under normal voltage conditions, you know what i mean? I dont know enough about tuning to know if this would effect it or not, thats what i am trying to find out. I would assume so cause i would guess that spark plug firing might be hindered and ignition timing alittle off maybe, or A/f ratio tuned towards a weaker/stronger spark due to mis-voltage... i dont know?

See here:

https://my350z.com/forum/exterior-an...using-ecu.html

https://my350z.com/forum/engine-and-...blem-help.html

https://my350z.com/forum/maintenance...eleration.html

https://my350z.com/forum/exterior-an...t-led-fix.html

 

You are missing a huge factor. ya the tail lights light up when the brake light is depressed BUT it's a different circuit. The tail light portion that runs all the time IS NOT TIED INTO THE BRAKE LIGHT. It's a separate wire that runs to it.

When you pull that fuse you still have tail lights, but no brake lights. You know why? separate circuits. The tail light circuit has ZERO to do with the brake light cicuit. Promise. Pull out the wiring diagram for the car and trace it.

also, another thing, if you have your lights completely off then there is no power going to the tails so how would that affect your acceleration? ever thing of that? Can't sense the wrong voltage when there is no voltage going to it.

you can change the tail light theory around, but i'm going to tell you 100% it has nothing to do with it. Something else is up with your tune unless you drive around with your brake light on the whole time. What was the humidity and ambient temp when you had it tuned compared to now? I know in the last 3 weeks i've had to adjust my tune do to weather conditions alone.

 

also, as you can see in all of those threads for ever 1 person that has had a problem (so far i've only seen 3 people in all of the threads) there are 10 people that have them with no issues. Seems too random to be directly related to a common issue.

If you still believe it then do the resistor thing they did. I think there has to be something else screwed up in the wiring.

 

Did you even read any of the threads? LOL

Ok then,

WHY is there a fix for these tails by installing a regulator?

WHY have people taken them off and had that make problems go away??

WHY when i took mine off, problems went away???

WHY has it been shown that they emit different voltage, and any car enthusiast/mechanic whatever knows voltage issues can cause irratic performance via the ECU??

WHY are people's Z's hesistant when accelerating???

WHY did more people chime in saying "Hey, mine do/did that buddy!"

DId removing the tails just magically change the performance for all these guys and make the problems go away?!?

I understand what your saying, I have from the start, but your ignoring the fact that this has happened multiple times to different people and that taking the tails off FIXED THE PROBLEM.

MY PROBLEM IS FIXED WITH THE HESITATION!!!, now im just wondering if i should get a retune.....THERE IS NOTHING WRONG WITH THE TUNE NOW, im just wondering if it can be better!!!

THE CAR PERFORMS MUCH BETTER THAN IT DID WITH THE LED TAILS ON!!!

Damn bro, i appreciate your help but your missing the main points here.

 

Did you not read the threads?!

Just the first one there is DOUBLE the people saying they had problems then those who didnt! I dont understand how your counting just 3 in all the threads???...cause there is like 5 in the first thread alone!!

Even if i am mistaking what with the taillights caused the PREVIOUS problem i had, it is pretty damn clear that the tail lights ARE IN FACT CAUSING THE PROBLEM.

Look at the first thread:

Chebosto and I at first said the SAME EXACT thing you are now...."No way it could be the tail lights". THen, obviously, we both did some more reading and then it became CLEARLY evident that the taillights WERE THE PROBLEM, hence Ches saying "I stand corrected" and me with my comments...












....Common man?

 

i read them. go count the people. 3 people out of 5 threads have had the problem. Now count the numbers that post that they had zero issues.

Like i said, try their "fix" if you want but 11 years experience building engines and tuning racebikes and now cars would not lead me in that direction if you brought this car to me. I would be looking elsewhere for another electrical issue.

 

binder, I don't think this is the pin 101 signaling issue - same thing we all thought. There is something weird going on. I think it may well be a glitch related to circuit design and not decipherable just looking at the FSM because I've tried to figure it out before and couldn't find how they could be related. However, multiple folks have reported resolution going back to OEM tail lights.

GeauxLadyZ, I don't think a retune is necessary. Any slight change would likely be within the adaptable range of the stock ECU. If there was a major operating glitch while tuning, it would've been obvious to the tuner...

 

From 1st thread alone i listed:

This one not on Z, but quote for reference, and not counting:
No problems:


6 counting Vas and not the Audi that had problems

2 that had them and didnt have problems.

6>2

I say thats enough to say its not a random coincidence... unless all of us who happen to have these tails also have similar electrical problems that are not related to the identical tails we have, but also that removing these tails happened to fix all of our electrical problems that were not related to our identical tails in any way.

I'm also sure the 3 dealerships Vas went to also had mechanics with 11+ years who couldnt figure it out either.... Just sayin...

 

i just can't wrap my head around that looking at this wiring though. Unless it screws up something else besides that brake light circuit there is just no way.

what else would that circuit board tie into that could affect the ecu? i've been looking it over and i can't seem to see a single crossover. It obviously has to be a defective part causing the issue since there are quite a few people running the same part and no issues. So defective part causing interferance somewhere with no visible link between them. weird. I truthfully would still try to isolate other issues too.

 

Awesome to hear, this was what i was hoping would be the case. I just didnt/dont know how severe this electrical issue with the tails was.

All i could figure out was that the difference was VERY easily noticeable in overall performance when i removed the LED tails last night. So that got me thinking that maybe pre-tune, the problem might have been enough to make optimal performance parameters outside of the ECU's adjustment area and thereby the ECU to move settings to one extreme of its working parameters in an attempt to adjust itself. Then when tuned, the tuner shifted parameters to where they otherwise would not be without this electrical issue, but what the car at the time was telling him were the optimal parameters...If all that makes any sense. Like i said, im still learning about tuning.

This taillight issue is indeed very strange, and difficult to grasp as well. It sure was for me, but i had all the underlying issues so i thought i would give it a shot and trying removing them. The effects were too great to be a placebo type deal.

 

Yes but the Brake lights circuit ties into the ECU, correct? You seem to know more about electrical than I so is it possible that the LEDs are mistakenly sending a constant low voltage to the ECU via brake circuit and this brake sensor or ECU is constantly picking it up, even though actual brake lights are not being emitted because voltage isnt enough?

If its only the brake light circuit that ties into ECU via brake light sensor, then that circuit has to be the, or is carrying, the problem, right?

Is it possible the brake light circuit is carrying a current dispite the fact that it's not enough to physically eluminate the LEDs unless more current is sent via pressing the brake pedal? This low current is, however, enough to trip the brake light sensor and therefore throttle down engine?

 

this is the only theory that proved ok, until you look at the diagram. The brake light switch is inline between the ecu and the brake light. Technically with the brake light switch disengaged there is no physical connection between the ecu and the brake light circuit at all therefore no way that even a low voltage bleeding into that site could affect it. The voltage leak would have to be between the brake switch and the ecu in which there is no connection.

hmm, that's the confusing part that basiclly says there is no physical way of a low voltage getting across.

your theory sounds perfect and i understand it completely. Say it takes 4v to activate the throttle cut and 5v to activate the rear brake lights. so if the tails are crossed and putting out 4v the throttle cut would be going but no brake lights. The brake light switch physically disconnecting the circuits kills this theory though.

also, the other problem is you're having decreased performance. The throttle cut is a HARD throttle cut. You can see how hard it is by given it some good amount of throttle while driving then gently push the brake pedal til the rear lights come on. it shuts it down hard. So there wouldn't be a "decrease" in performance there owuld be a severe loss andit would just fall on it's face (which was vas's issue after 3k, it just basically died after 3k)

That's the second half of the issue. The throttle cut is all or nothing, not just slight.

 

I dont get it man, but the problem has to there somewhere. This guy chimed in on Vas's thread.....sounds like he knows what hes saying from experience but who the hell knows where he got this knowledge or if he knows what hes talking about:

"LOL same here, sorry for coming late but I could have told you right away it was your brake light circuitry... cruise fails because of current bleed through OEM/modified brake light wiring, making the ECU think you're constantly laying on the brakes, and at the same time cutting throttle assuming your gas pedal is probably stuck."

 

Also, with this, i hear what your saying but how do you know what the throttle cut would feel like if was constantly trying to "hard cut" while at the same time your physically depressing the accelerator and NOT pressing the brake pedal, so car doesnt have brakes in assisting its automatic deceleration of the car. I would assume in this instance the acceleration would win, or it would be a stale mate like the "falling off" guys are describing at certain RPMs.

Does this make any sense?

 

Kevin Pierson has problems with his electronic module that simulated a 1 sec press of the brake pedal to prevent the CEL from just disconnecting pin 101 (to allow brake boosting). Only some cars had issues. Alberto had weird throttle issues. SFLG had cruise control failure. That is one odd circuit... Hardware design issue most likely, not a flaw in the logic diagrams as outlined in the FSM.

 

i think what you're trying to say is you think the "hard" throttle cut i'm feeling is the brakes? the answer is no. Just barely touching the brake is all it takes for that light in the rear to come on. The brake light will light up much sooner than the actual brake pads forcing down onto the rotors.

you can test this on your own. just gently press the brake until you see your 3rd light come on. The brakes might just barely be engaged at this point but most of the time not. Slam down the gas pedal and tell me what it does. You'll see what i mean by hard cut. It's not the brakes that are causing the decel, is the cut of fuel.

you can also test this by trying to do a standing burnout in which the car is moving zero miles per hour. Do that and when the accelerator just kills the car you'll see that it's not just a 'bog" it's a huge cut in fuel.

The computer doesn't have degrees of accel cut for the vdc circuit. It's a switch so it's either cut or not cut. There is no reduction or only a 10% cut one time and 30% cut the next.