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normanahoyt
normanahoyt, ASE Certified Technician
Category: Nissan
Satisfied Customers: 371
Experience:  I am a Nissan trained technician and a foreign car specialist
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Nissan/Datsun Altima 2.5S: Hi, I have a nissan altima 2002

Customer Question

Hi,
I have a nissan altima 2002 2.5S 62343 miles.I don't have ignition signal to coil and of course no spark.When i try to scan it i cannot communicate with the ECM.The scanner says error communicating,check fuses,ground if ignition is on.I have checked all this and is they are all ok.I check signal to ignition coil with scope and there is no signal going from ecu to ignition coil to get spark.The injectors are getting signal because i can hear them activate when cranking the engine.I need help with this car.I have the official nissan workshop and have measure all according to the book and nothing wrong so far.
thanks
Submitted: 2 years ago.
Category: Nissan
Expert:  Clifton B. replied 2 years ago.
hi. is the key light on on the dash? did you check all the fuses inside and under the hood ?
Customer: replied 2 years ago.
Hi there,

Ther is no key light on the dash.But it has been checked with a consult and it was ok with the key.When i turn on ignition swith,,should the key light come on?But now it cannot even read the ecm for trouble codes.
thanks
Expert:  Clifton B. replied 2 years ago.
ok if the consult cannot read the ecm then you may ether have a bad ecm or the power and or ground to the ecm is bad . since you have replace the ecm then you will need to check for power and ground to the ecm , you will need to check for power at pin number 12.42,109 and 111 ,with the key on and ground at pin 59,60,108 and 106
Customer: replied 2 years ago.
There is power at pin 12,42,109 & 106.Also the pins 59,60,108 & 106 for ground has been checked and is ok.
Expert:  Clifton B. replied 2 years ago.
the key light on the dash dose it go off when your trying to start the car ? and did you reprogram the key after your eplace the ecm /
Customer: replied 2 years ago.
there is no key light coming on,when ignition is on neither when try to start the car.This car stop suddenly on street and was towed home.We scan it and found nothing that day.But one thing i notice was the fanmotors coming on when try to start the car.I have a friend working at the dealer here and he told the ecu must be replace.ok,i ordered an ecu from the state and he program it with consult,but still no spark when cranking.After that we didn't do anything more with the car.And this week after some months that the car is here i will get it fixed.The nissan friend here dont know what to do.Also crank and cam sensors have been changed.
Expert:  Clifton B. replied 2 years ago.
if you have no communication with the ecm and the fans run all the time when the key is on then you have a power or ground problem at the ecm , you need to recheck the fuses and the wire i told you to check at the ecm , am think you have at a power or ground problem so just recheck it .
Customer: replied 2 years ago.
I think i was not good understand.When the car was towed here the very first time the ECU runs the fan motors with ignition on.We have changed the ECU and the fans are not running any more.Also the new ecu has been progammed.So now fan are not running,only thing we are sitting with is the signal not going to coil for spark.All grounds have been rechecked,cleaned retight also voltage is present avery where the manual indicated.
thanks
Expert:  Clifton B. replied 2 years ago.
but now you have no communication right
Customer: replied 2 years ago.
Correct.No communication.
Expert:  Clifton B. replied 2 years ago.
did you have before you replace the ecm
Customer: replied 2 years ago.
After the ecu was replaced we do have communication.Only thing i can remember that happen.The battery discharged after long cranking, and we changed it for another good charged battery.One of the terminal was not enough tighten and was losing contact, so we tight the terminal good for contact and after that changing of battery show up the no communication.Thats the only thing,but i don't think that may cause any problem.
Expert:  Clifton B. replied 2 years ago.
ok try this disconnect both battery cable and hold them touching for 5 minutes then see if you have communication , if the ecm have gone into lock mode this will unlock it .
Customer: replied 2 years ago.
Has been already done.It is very strange with the signal to coil.The cam and crank signal is reaching the ecu.Ecu is sending signal to injectors but not to ignition coil.
Expert:  Clifton B. replied 2 years ago.

did you check for power at the red wire and ground at the block wire at the coils

Customer: replied 2 years ago.
Yes.power and ground are present there.
Expert:  Clifton B. replied 2 years ago.
ok lets look at what you got , 1 you have power and ground at the ecm ,2 you have power and ground at the coil but no signal from the ecm to the coils , 3 the key light is not no 4 you have cam and crank signal, 5 you have injector signal , 6 you have communication , since you have all that the only thing to say at this point is that you have a bad computer , now i know you just replaced it but there is nothing els to blame for this problem , i would get a different computer . the coils signal is coming from the computer and all you need for it to work is power and ground if you have that and it still don't work then the computer is bad .....
Customer: replied 2 years ago.
ok, the dealer tech came with an ecu.This ecu was replaced due to cylinder # 2 misfiring.
But due to the problem with no communication he could not program this ecu to test for signal on coils.
If i can get it the scanner to communicate with the car than he can test the other ecu.
Expert:  Clifton B. replied 2 years ago.
sound good. and you do have communication now so just plug that other ecm in reset the keys and see what happens
Customer: replied 2 years ago.
No the communication problem is still there.
1.no signal to coil.
2. no communication
Expert:  Clifton B. replied 2 years ago.
if you have power and ground to the ecm then you should have communication , you should check for power and ground at the dlc connector to make sure that is working.you need to check for power at pin 8 and 16 and ground at pin 4 and5 then check the k line wire at pin 7 to pin 50 of the ecmfor continuity
Customer: replied 2 years ago.
I will check this tomorrow and will get back to you.It's here 9.11 pm
Expert:  Clifton B. replied 2 years ago.
ok
Customer: replied 2 years ago.
Hi,
I wish you have a pleasant day today.
I checked pin at dlc conn.
pin 8 & 16 voltage present
pin 4 & 5 ground present
pin 7 dlc and pin 50 ecu continuity present.
Expert:  Clifton B. replied 2 years ago.
then you need to swap the ecm there is nothing les to check >>>
Customer: replied 2 years ago.
when i swap it how to program key if it not communicate with the scanner
Expert:  Clifton B. replied 2 years ago.
if it is not communicating then ether the scanner is bad or the and ecm have a power or ground problem
Customer: replied 2 years ago.
3 scanners can be bad.Consult,Launch 431Tool, otc genesis.Another ecu has been tested.I will ask a friend for another ecu from an Altima he has in his shop.
thanks
Expert:  Clifton B. replied 2 years ago.
ok the is car have a problem with power or ground that you will need to fine
Customer: replied 2 years ago.
Will be rechecked.
Expert:  Clifton B. replied 2 years ago.
ok
Customer: replied 2 years ago.
Relist: Other.
I still have the very same problem.No solution to my problem with the car.The tech didn't tell me anything new.All he says i have done already.
thanks
Expert:  normanahoyt replied 2 years ago.
Hello, my name is Alan and I am here to assist you
Expert:  normanahoyt replied 2 years ago.

I just read the long story and at a glance it would look correct as to the new PCM having gone bad. When you have a spark like you had at the battery due to a poor connection there is always the risk of damaging the PCM.

 

Let me look at this thoroughly and get back to you here in a bit with a diagnostic process.

Expert:  normanahoyt replied 2 years ago.

The communication with the scanner is the one we need to address first.

 

Here is what I would like you to do first. Check the ground wires that hook to the intake manifold. These will break and it is possible that you may be getting a reading with a volt meter and yet not have a strong enough ground to boot up the ecm. Pull on them and make sure that they are good and strong.

 

The next thing is to check fuse #19 in the underdash fuse box which is the power for the scanner.

 

If both of these are good then we will move on.

 

Please let me know your results.

 

 

Customer: replied 2 years ago.
ok,
will do that and let you know.
Expert:  normanahoyt replied 2 years ago.

Ok, I'll check back a little later

Customer: replied 2 years ago.
I will do it this sunday and get back to you afternoon sunday.I am very busy this week.
Expert:  normanahoyt replied 2 years ago.

OK, I will look for your response Sunday

Customer: replied 2 years ago.
Hi Normanahoyt,

How are you doing.Sorry for the delay.But i hadn't time for this car.I am making some time to spend on it these days.
I have checked what you suggest me to check and all looks ok.Ground wires are not broken and also fuse #19 is ok.i unplug the O2 sensor and then the signal tends to raise a little bit but not enough to get the coil to spark.
thanks,
Expert:  normanahoyt replied 2 years ago.
I am out of town but will look at this this evening
Customer: replied 2 years ago.
ok. thanks
Customer: replied 2 years ago.
Hi normanahoyt,

Did you have a chance to look out for something.
thanks
Expert:  normanahoyt replied 2 years ago.

Sorry about the delay, here are the tests that need to be done. I have a sinking feeling that the replacement ecm may be damaged but we must do these tests.

Vehicle Application:
2002 Altima 2.5
Customer Concern: No start. No spark. No fuel pressure. No fuel injector pulse. There is no communication with the scan tool.
Average Reported Mileage: 131312
Tests/Procedures: 1. Check powers and grounds to the Electronic Control Module (ECM). Verify there is key on battery voltage to terminal #42 of the ECM. Then if the grounds are good on terminals 59, 60, 106, 108 the ECM should ground terminal #20 to turn on the ECM relay. Then when the relay turns on there should be battery voltage to ECM terminals #109 and 111.

2. If the key-on power and ground are good and the ECM will not ground terminal #20, then check for a shorted 5-volt reference voltage to the throttle position sensors and other sensors. Also try grounding terminal #20 and see if the ECM wakes up and the vehicle runs.

Customer: replied 2 years ago.
Hi,

Powers and ground to the ECM are ok.Also it ground ecm relay in IPDM engine room.Then i got voltage at terminal 109 & 111.
I have notice something very strange.While cranking one of the ECU side become very hot and that with both ecms.Also i notice the tacho needle wont move while cranking.My own mazda RX8 while cranking i got a 200 rpm before engine start.
Should i got some rpm on the tacho while cranking on this car.
Expert:  normanahoyt replied 2 years ago.

Due to the fact that the ECM is clearly not working even enough to get communication so the tach will not work until we resolve the root problem.

 

The way that we need to test grounds is by using what we call a "live circuit resitance test". Put one terminal of your volt meter to the ground that you want to check (with everything hooked up, put the other lead of the volt meter to the battery negative terminal and then crank the engine. If you get more than .05 volts then you will need to either find and fix that ground or add ground to that wire. You can do a positive voltage supply test in the same fashion by putting one lead of the volt meter to the supply wire and the other to the battery positive post. On some of those you may see up to .5 volts and still be ok.

 

I am quite certain that you will find one of the grounds that breaks down under the load of the pcm attempting to boot up and you will probably find a reading of 2 volts or higher at one or more grounds. It will be simpler to just piggy back some wires that you then bolt down firmly to a good ground.

 

Let me know what the results are of this test. Any typical tests that you have done are not reliable because if a ground wire is hanging on by one thread of copper somewhere it will measure like it is ground but it will not be able to carry the necessary load.

Customer: replied 2 years ago.
Hi,

I have not done this test,but i have bypass all the grounds and also the voltage to ecm and the same.I will do this test and let you know tomorrow or later on today.

thanks so far .
Expert:  normanahoyt replied 2 years ago.

Excellent. Unfortunately it all leads to "bad ecm" which you say you have replaced with others. The fact that it is getting hot is why I suspect that there is still a ground or power problem that could take out another ecm.

Customer: replied 2 years ago.
Hi,

Grounds read 0.4-0.6
Power 0.5-1.0 (1.0 on terminal 20)
I test all grounds with a ground wire from batt to ground terminals and the reading was the same.Also with voltage i did the same and the reading was the same.

thanks,
Expert:  normanahoyt replied 2 years ago.

#20 is not a power input. The instructions say that that is the ground output to the ecm relay. So with key on there should be a solid ground there. You can do what it says next and just ground that white/black wire and see if the ecm powers up but I suspect it won't.

The next thing they want checked is the reference voltage. #65 at the ecm should read 5 volts with the key on, check that and let me know what you have there.

Customer: replied 2 years ago.
Hi I got 11.6 volt on terminal #20.I will check # 65 in the morning and let you know.

thanks
Customer: replied 2 years ago.
Hi ,

Terminal # 65 give 5.0 volts.

thanks
Expert:  normanahoyt replied 2 years ago.

You don't mention grounding terminal 20....have you done that step and checking to see if you can then communicate with the ecm?

Customer: replied 2 years ago.
No i haven't try that.I will do it tomorrow and let you know the result.
thanks
Expert:  normanahoyt replied 2 years ago.
Excellent, I'll follow up tomorrow
Customer: replied 2 years ago.
Hi,

Grounding terminal # 20 and there is still no communication with ecm.
thanks
Expert:  normanahoyt replied 2 years ago.

Hello,

 

This thread is now so long that I need you to understand that I cannot remember or look through everything we have already "checked". So humor me and recheck some things if you already have checked them.

 

Here is a "no communication" concern to check out:

 

Vehicle Application:
2004 Altima 2.5 2006 Altima 2.5
2005 Altima 2.5
Customer Concern: Malfunction Indicator Light (MIL) is ON. No communication with scan tool. The Yellow/Red wire at terminal 16 of the Data Link Connector (DLC) has 3.4 volts. Fuse 19 is good. The dash gauges work and fuse 19 powers up the unified meter control unit too.
Average Reported Mileage: 63595
Tests/Procedures: 1. Jump battery voltage to the Yellow/Red wire at the DLC terminal 16 and see if the scan tool will communicate then to see what code is in the computer.

2. Check the harness on the Yellow/Red wire between the fuse box and the DLC.
Tech Tips: The Yellow/Red wire at the DLC should have 12 volts.

Customer: replied 2 years ago.
ok,
will check out these and let you know
Expert:  normanahoyt replied 2 years ago.
Good, talk to you later

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I am a Nissan trained technician and a foreign car specialist