Need help with ecm and engine wire harness questions! [Archive] - B15sentra.net - Nissan Sentra Forum

: Need help with ecm and engine wire harness questions!


#1spec-v-red
03-24-2010, 07:29 PM
I have a 2002 sentra spec-v.

I have a couple questions.

1st Where is the ecm located?
2nd How hard is it to replace and is it just plug and play after replacing does it require anything else like programming?
3rd I also have to replace the engine wire harness and wanting to no how long it usually takes for this to complete.


Dealership charging 2500 for both which is crazy. my car turns on but throws cam sensor but because the wiring is damaged not due to sensor. they said ecm is damaged due to short or not enough signal due to wire damaged but could that be accurate cuz car runs fine when I get it to turn on.

mirrortints
03-24-2010, 08:34 PM
You cant just replace the damaged wires?

But, anyways, the ecm is in the engine bay on the passenger side firewall. Its in a black box. Its plug n play...sorta. If you have the immobilizer, you will need to get your keys reprogrammed at the dealership.

The engine harness may take a few hours. But just make you you unplug and plug as you go. Thats the easiest way cause if you just unplug everything, you will forget where the new harness goes LOL

#1spec-v-red
03-24-2010, 08:51 PM
You cant just replace the damaged wires?

But, anyways, the ecm is in the engine bay on the passenger side firewall. Its in a black box. Its plug n play...sorta. If you have the immobilizer, you will need to get your keys reprogrammed at the dealership.

The engine harness may take a few hours. But just make you you unplug and plug as you go. Thats the easiest way cause if you just unplug everything, you will forget where the new harness goes LOL





Yes I have the immobilizer system. Do they charge to reprogram at the dealership?

So does that mean I won't be able to turn car on? or will I be able too...

I tried to redo the wiring to the sensor it didn't work still threw the code. that's when they said need new wiring harness.

mirrortints
03-24-2010, 09:05 PM
Well, you wont be able to turn the car on. Youd need to tow it in, unless you did the work in their parking lot.

Any chance you spliced into the wire and ran a new one? You may try to completely replace the the wire from the plug and run a new wire to the sensor.

Just throwing out ideas.

#1spec-v-red
03-24-2010, 09:17 PM
Well, you wont be able to turn the car on. Youd need to tow it in, unless you did the work in their parking lot.

Any chance you spliced into the wire and ran a new one? You may try to completely replace the the wire from the plug and run a new wire to the sensor.

Just throwing out ideas.

well i tried that and it still threw the cam sensor code it wont go away even bought a new plug. the car wont start but like 3 times a day after moving around wires. like it wants to start but wont turn over

#1spec-v-red
03-25-2010, 07:24 PM
Anyone else got some knowledge on this?

civiceater
03-26-2010, 01:07 PM
Well, the problem is that if you have a short, you will need to find where the short is. That means you need to trace the wire coming out of the sensor all the way to the ECM. Which means you'd have to open up your wiring harness and physically find that short. Did you already replace the ECM? It's also possible that the ECM is shorted internally and it's causing a "short" on the signal. The tech over at nissan doesn't know what he's doing as far as diagnosing where the short exactly is. He's trying to short cut it and replace both the ECM and the harness.

#1spec-v-red
03-26-2010, 02:37 PM
So do you think if I just replace the entire engine wire harness that will fix the problem(as fas engine tunring on and cam light coming off)?

Is it possible that the car wont turn on or turn over due to camshaft sensor?
Because if so then I will just replace the wire harness and ignor the ecm replacement that the dealer is stating.

I was also thinking that there is nothing wrong with the ecm. Unless that is causing the car from turning on. But seems unlikely cuz when it does run it runs fine just the rpms go up and down while on idle. Which I figured it would be the cam sensor due to no full signal, right?


Well, the problem is that if you have a short, you will need to find where the short is. That means you need to trace the wire coming out of the sensor all the way to the ECM. Which means you'd have to open up your wiring harness and physically find that short. Did you already replace the ECM? It's also possible that the ECM is shorted internally and it's causing a "short" on the signal. The tech over at nissan doesn't know what he's doing as far as diagnosing where the short exactly is. He's trying to short cut it and replace both the ECM and the harness.

civiceater
03-29-2010, 12:01 PM
Like I said, the code is caused by a short in the circuit. The circuit includes from the sensor, wire harness and into the ECM. The short can be anywhere in between those 3 components. The sensor could have an internal short which will cause that problem, the wiring harness could have a short and cause the same problem, or the ECM itself has a short internally that can again cause the same problem.

I'd say, do the cheapest first which is your sensor. You can get a set of cam and crank sensor under the TSB part number (which at the moment I can't remember) for around $50. If that doesn't fix it, I say do the manual labor of tracing the wiring from the sensor all the way to the ECM. Also if you know how to do this, you can separate the actual wiring from the connector on the ECM to actually eliminate the connector as a problem. After you've confirmed that the wiring harness doesn't have any short on that signal wire, then I'd have to conclude that the ECM is your culprit. It can have an internal short on the circuit that the cam sensor runs on. You could also find a buddy who is willing to lend you an ECM to see if you can eliminate the ECM from your list. Good luck.

timmytheSpecV
04-01-2010, 02:25 PM
I would consider myself an expert with this problem since I wasted 2 months of time replacing everything when the problem was just the wiring harness. I would say look for a problem with your main wiring harness under the corner of the radiator on the side where the battery is located--these cars had a horrible design for the location of the main harness IMHO.

The dealer told me the same thing at first- "the ECU has a short". My experience has been that their immediate logic is always lets replace everything and we don't actually have to find the problem. If they replace enough stuff, they are bound to fix it.

DO NOT LET THEM LIE TO YOU.

$2500 to fix this problem = RAPE.

Find a good electrical guy who fixes nissan electrical problems and it shouldnt cost more than $300-400 depending on how quickly he locates the problem. I would have him check right away for corrosion on the wires right below the battery and the fusible link box near the radiator - it may save you an hour or two on labor.

If you know the wiring is solid, then go buy a used ECU/ECM with low miles on it from a junkyard - www.car-part.com Just make sure it matches your model + it's features.

Replacing the ECM/ECU takes about 10 mins. Remove the strut tower bar, unscrew some screws and carefully remove the box, undo the ECU/ECM protector box, pop the old one out, pop the new one in, and reverse the process. Even I can do this with the limited amount of tools I have.

In the end, I spent $390 to have a reputable Nissan dealership ONLY fix the wiring problem and the problem was solved. I imagine you will have to spend a lot less since you probably have the same issue and you now know more than likely where the problem is located. Tell whoever helps you to start at the part of the harness near the radiator under the battery and they wont waste time looking elsewhere.

Hope this helps.

mirrortints
04-01-2010, 02:29 PM
Replacing the ECM/ECU takes about 10 mins. Remove the strut tower bar, unscrew some screws and carefully remove the box, undo the ECU/ECM protector box, pop the old one out, pop the new one in, and reverse the process. Even I can do this with the limited amount of tools I have.

I have a question, the vehicle immobilizer?

timmytheSpecV
04-01-2010, 04:27 PM
I have a question, the vehicle immobilizer?

What about it?

mirrortints
04-01-2010, 04:28 PM
When you swap ecu's, what do you do about the immobilizer?

timmytheSpecV
04-02-2010, 08:23 AM
When you swap ecu's, what do you do about the immobilizer?

If your car has it, you make sure you get an ECU that has it. Basically when you take out your ECU, there is a code on the back. For example: 5ZE15P equates to a spec v model with immobilizer + all options. If you can match some letters and numbers, you can do it too. YIPPIE!!!

What this means is when you go to www.car-part.com , make sure you match the ECU or you will waste your time and money.

One last thing, after you swap the ECU, you need to reprogram some things like your keys and idle air controller. You can do the latter yourself, the keys will need to be programmed by the dealership.

Hope this helps. :)