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  #1  
Old 12-14-2013, 10:25 AM
madmantrapper madmantrapper is offline
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Default 2006 Altima ignition system

Is there anyone on here that really knows how it works? What the sensors actually do and how the computer processes the info? Is there a place where you can get a schematic of the ECM? I am looking for answers that no one seems to be able to give me, not even Nissan. I am convinced that all the techs at the dealers know is to keep throwing parts at it til it works again.
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  #2  
Old 12-15-2013, 03:28 PM
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bennyb53 bennyb53 is offline
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Quote:
Originally Posted by madmantrapper View Post
Is there anyone on here that really knows how it works? What the sensors actually do and how the computer processes the info? Is there a place where you can get a schematic of the ECM? I am looking for answers that no one seems to be able to give me, not even Nissan. I am convinced that all the techs at the dealers know is to keep throwing parts at it til it works again.
In your other post you reported a No Start condition. You also said, "CEL is not lit and no trouble codes. A no start condition is the most frustrating because it covers pretty much your entire system (charging, ignition, fuel delivery, electrical system, etc.). In some cases life is a bit easier when a code is present such as a code P0335 for faulty crrankshaft sensor, or code P1610-1615 for NATS that prevent a no start. But with a no code, it tells me the fault is somewhere where it is not monitored by the computer such as low batt., loose batt. connection specially the neg. cable at chassis and engine, faulty ignition switch, ecm relay, fuse and fuseable links, faulty starter, open circuit, faulty PCV valve etc., etc., etc.

Please be specific as to what sensors you are referring to. You will find all sensors and its functions in the Engine Control manual. You will also find the ECM schematics in Circuit Diagram section of the manual. All manuals are in the Knowledgebase section at the top menu tab. Happy Troubleshooting.
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Old 12-16-2013, 01:48 PM
madmantrapper madmantrapper is offline
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I don't want to be disrespectful so I will not comment on your comments.
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Old 12-16-2013, 10:50 PM
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bennyb53 bennyb53 is offline
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LOL - no worries I am not that sensitive. But I expected you to exercise your First Amendment Right to free speech.
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Old 12-19-2013, 11:45 AM
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So in this day of electronics we all think there's something wrong with the computer causing all our problems. I myself used to be of the same opinion. Then I had an event occur that when finally solved ended up being just good old mechanical aptitude. With this said our engines still need the same 4 things to start and run as they always have:
1. Spark
2. Fuel
3. Timing
4. Compression

The brains of the engine control system uses various sensors to determine physical characteristics of the engine's state and then adjusts controls to meet it's programming. The Nissan EC section of the Factory Shop Manual has a pretty good diagnosis chart of what to check for various modes and all DTC's. There is an SAE spec that covers what all OEM's must comply with for OBDII systems in their cars.

Something for the OP to consider is the non electronic aspects of engine operation as part of the over all troubleshooting scheme. such as: what does it sound like when cranking, what is the compression, is there fuel to the rail as starters.
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Old 12-19-2013, 02:09 PM
madmantrapper madmantrapper is offline
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jlg2002,

Thanks for your comments. I understand all of that very well. What I am looking for is how it all comes together. What the ECM looks at to determine what decisions to make. I don't think the control is at fault, I just want to know how it processes the information from the sensors. My gut feel is it is not very complicated. I can't believe Nissan service folks don't know how it all comes together.


edit: Can you tell me what tells the ECM what cylinder is coming up on the power stroke so it knows which plug to fire?

Last edited by madmantrapper; 12-19-2013 at 02:14 PM. Reason: added
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Old 12-19-2013, 05:16 PM
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bennyb53 bennyb53 is offline
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Quote:
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edit: Can you tell me what tells the ECM what cylinder is coming up on the power stroke so it knows which plug to fire?
The answer is the camshaft position sensor. I may have a pic of it in the photo gallery. The back-end of the intake camshaft has teeth in which the cam sensor is facing. It senses the position of the piston. It works in tandem with crankshaft position sensor to determine overall timing.

Most techs knows specially ASE techs. They are not paid to give lessons to every customers with inquiring mind like me or you. If I were a tech I wouldn't waste my time cuz most of them have no clue and what I say just go right out the door.
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Old 12-20-2013, 02:45 AM
madmantrapper madmantrapper is offline
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bennyb53,

If you are right and it is the cam shaft sensor, how can the engine run with it disconnected?
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Old 12-20-2013, 10:29 PM
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Quote:
Originally Posted by madmantrapper View Post
bennyb53,

If you are right and it is the cam shaft sensor, how can the engine run with it disconnected?
How can you make the engine run with cam sensor unplug? I don't know, lol. For modern cars, I say modern, I'm referring to OBD II compliant vehicles. And they are from 1996-to the present models. They are equipped with engine management system to control overall engine performance. EMS is simply the onboard computer which we commonly refer to as the ECM in Nissan world. Do an experiment with your engine idling and unplug the CPS. Reconnect and restart and tell us the result of both. And by the way, fuel is injected on compression stroke and not on power stroke as you've stated in #6.

In my last post, I did not address your other question in thread #6. You asked: How does the ECM processes the data to make the decision. And you think its not complicated. It is a computer, it has a motherboard-a printed circuit board, it has a controller chip where the software is loaded and it has a microprocessor (cpu), just like your desktop or laptop. The similarities end there. It is customized for one purpose. The cpu can make calculations at 2 millionth of a second. To put it in perspective, a blink of an eye is 300-400 millionth of a second.

The ECM has a drive map. It is nothing more than a look up table of pre-set values. Take for example the Air Fuel ratio sensor. On my Altima it is oxygen sensor. The same function but slightly different system. In the perfect world we should be getting the ratio of 14.7:1 air fuel ratio or 0.45v cuz computer can't read C or F or angles so everything is converted to voltage. Do you live in a perfect world? I don't. Road conditions, load factor, driving habits, etc. all affect gas mileage. The feedback sent by the sensor, ECM will look up the Fuel Trim table and make calculations as to put more gas by keeping the injector open a bit longer or decrease gas by shortening the time injector is open. It does this up to 10x/sec. The data on a particular trip will be in Shor-Term Fuel Trim whereas the accumulated adjustments over time will be in Long-Term fuel trim. When the adjustments reaches a max of 25% of base value, ECM no longer makes adjustment and decides to set a code.

Another good example is the Engine Coolant Temp. sensor (ECT). At cold start, resistance is high say 2.0v. As engine warms up resistance goes down so when engine reaches normal operating temp. say 180F resistance say at 0.3v and T-stat opens up. But if T-stat remain open from start up, ECM gets a signal engine hasn't reach normal op. temp. therefore it cannot go into a Close Loop, and it will trigger a code.

I am away from my home base in the next 2weeks so I Wish All The Happiest of Holidays......Merry Christmas and Happy New!
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  #10  
Old 12-21-2013, 05:43 PM
madmantrapper madmantrapper is offline
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bennyb53,

Thank you for something that makes sense. If I disconnect the cms while running it keeps running. No code thrown.
Plug it back in and it still runs fine, no code thrown.
By the way resistance is read in ohms not volts. Just splitting hairs after the comment about power stroke vs compression.
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  #11  
Old 12-22-2013, 10:16 AM
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Oops! thanks for the correction. My trend of thoughts are voltage and resistance are higher at cold start and decreases as temp. increases. I admit didn't proof read it. Would also want to add "Year" at the end of last sentence, (:.

That is what I've gathered from guys who say when engine is running, unplug the CMS, engine continues to run, however, when you shut it down it won't restart. That is an improvement that ECM goes into default Fail-Safe mode when it no longer receiving feedback from CMS. For older models engine just quit as in my 02 Altima.
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