04 nissan sentra no start

[skm]

I had a car towed to me from another shop, 04 sentra no start this shop had it for 2 weeks can not figure it out. (the other shop had replaced almost every sensor on the car including cam and crank sensors twice) so I crank the car I have a rpm signal good crank sensor good, manually check the cam sensor good operation. Decide to check no spark or injection pulse, cranked it several times every once in a while at the start of the cranking I would get a quick injection pulse and spark. Unplugged an injector found power on both sides of the injector harness, checked the rest of the injectors same thing. So Bad injector driver in the computer? I do not have the wiring diagram at this time since our internet at work is down (switching to another company) so I can't access shopkey pro. Then I started thinking why is my spark doing the same thing? Security of some sort? The car has a metal key not chipped so I wouldn't think so . I had my scanner scan all systems of the car and it has nats v5 , now I still don't have any internet so I can't find any info on this does anyone have any insight about nats v5 before I condemn this guys computer? or is it just some fluke thing that nats v5 shows up and it really isn't anything at all? I did check codes with the scanner for security it says no codes. so I don't know with out some wiring diagrams and info on the security system. The only other thing I have not checked since on wiring diagrams is grounds for the computer.

 

thanks

Edited February 5, 2016 by skm

[carolinahigear]

I would eliminate grounds being the problem right off the bat. We have seen many similar no-starts lately with bad grounds. They will fool you into thinking it's a NATS security problem.

[skm]

okay so I checked grounds all good, have no codes setting in the computer, even though when all systems are scanned comes up with nats 5.0 I think this is strange since this is not a chipped key even pulled the column cover to verify no receiver on top of tumbler. As I mentioned in the first post this car has been at another shop. I may be over looking some thing here. On some key cycles you get a injection pulse and spark for a brief second then it is gone. cam signal and crank signal always at the computer manually verified this.The injector harness unplugged shows voltage on both sides. All other data looks good. not 100% sure how the pedal sensor works with the tps, they both start with the same voltage where a lot of other cars I have come across the pedal starts at 5 volts and works down as it depressed and the tps starts low and goes high. I am unable to verify how this system works if it works like this I would assume so since I get a percentage of throttle opening, but I may be wrong. Could it be in some sort of clear flood mode? I don't get to see much data on my scanner very limited. my other thought is that may it of jumped timing? It does not set and cam codes, but there also doesn't seem to be any data stream for cam sync either so I guess monday I will verify timing . I Just really dont think it is the computer there is something I am over looking . been a very busy week so have not had a lot of time to spend on it. ANy insight would be appreciated thanks.

[xrac]

Understand that I am not a tech but I think I would check cylinder compression?

[b1qwkbird]

Do you have access to a labscope? If so then make sure the cam and crank signals are in sync. If the reading is implausible the computer may be shutting off spark and fuel to avoid further engine damage. This would be easier than pulling the timing cover. Also as Frank suggested a compression check may point you to a cam timing problem as well with a consistently high or low reading.

Edited February 6, 2016 by b1qwkbird

[Jeff]

You said the other shop replaced everything..possible they installed a used ecm?

[skm]

Xrac, that is what I plan on doing Monday. b1qwbird, no access to a lab scope, but that is my thoughts at this time. I will set it on tdc and pull the valve cover and see where the cams sits. Jeff, I talked to the other shop yesterday they didn't try another computer, but I don't believe it is the cause. Thank you guys for the input, I am very strongly leaning towards timing being the issue as you see I am was leaning towards that on my last post. The reason I have not checked that so far is I would of thought the other shop would of done that, but you know what they say to assume makes and ass out of u and me. So that is my fault. When I was talking to the other shop yesterday they did say that they car came in a few weeks ago throwing a cam code they replaced the sensor , a week later it did it again so I am very much leaning towards the timing.

I am think as b1qwbird said it is so far off that it kills the spark and injection and it does it before it has met the parameters for the setting of the cam sensor code. I will check things out Monday and let you guys know what I find. My problem is that we had 2 feet of snow the other week and were terribly slow and now we are extremely busy and I need to turn some work out so I have sort of put it on the back burner not to mention it is someone else's problem they dumped on me. anyway I will let you guys know what I find thanks !

Edited February 6, 2016 by skm

[xrac]

We had something similar a few weeks back on a 95 Avalon. After we wasted a couple of hours my guys said it was a wiring problem. The wiring in this car was a mess and all esposed and they didn't want to work on it. Honestly, I didn't want to work on it either but it was for a friend. The next day after talking to a guy who use to work for me I had a one of my guys check compression. Bingo!

[SMMotors]

I'm with Jeff, you sure the other shop didn't put in a used ECM? You shouldn't be able to communicate with nats if it's not supposed to be there

 

Condemning the ECM would be the last thing I would be doing. Just because you have no injector pulse doesn't mean the ECM is bad. You have no injector OR SPARK.

 

No need to go through all that work of pulling the valve cover off to check timing. What's your cam degree reading during cranking? What is bk1 vs bk2? For every 15* off! that is one tooth.

 

Since you already pulled the coils, check compression, but I don't think that's the issue. Read up how the system determins spark and fuel pulse and start there. There's no way the injector driver and spark driver went out. Look at the ECM that's in there and check for salvage yard writing.

 

Let me know what your cam readings are on the scanner.

[skm]

SMMotors, yes like I said I didn't think it is the ecm because of the loss of spark and injection pulse. I also stated that I have very limited data on this car for what ever reason. This is a 1.8L engine not a v6. I did pull the Valve cover and look at timing . It is 2 teeth off on the intake cam. Of course the intake cam has the cam sensor on the back end of it. The other shop got hold of the customer and they don't want to fix the car. I guess it was all just a learning experience . It is strange how some cars you can get a useful amount of data and others you can't, that also plays into what scanner you are using. I do appreciate all the input you guys gave . I am going to look up and see what the parameters for setting a cam sensor code in this car is, since it does not set any codes during cranking. Happy wrenching turning to all

Edited February 9, 2016 by skm