no spark?

[bayonnite]

hey guys, this my first post and am sorry to skip my intro, but am in jam right now. ive got a 99 denali 5.7 r motor and yesterday my motor cut out on the nj turnpike so i get it home started working on it to find i have no spark whatsoever so make a long story short i changed ignition module, coil, cap and rotor, all of witch i recently replaced, as well as the plugs and wires, all to no avail, still no spark, i also turned the motor by hand to see if the rotor was still spining with the motor and it is so timing chain is still intact, so thats where am at, what else could cause no spark?? i have no idea. does the ecm cotrol spark, maybe my computer is fried? i really need some of your input on this, cause im just stumped. thanks guys!

 

[GMCYukalade]

yeah, the ECM does - however, if you get under the hood to the fuse box on the drivers side there are two relays in there, might want to check them - i'm not sure about the exact specifics of them, i just know if you take either of them out.. motor will not crank - if your looking at the fuse box from the front of the vehicle, and the top of it is off, it is the two relays on the left side top and middle - the bottom one will be the fuel pump relay - it says what they are on the fuse box cover - now.. if i remember correctly if you take one of them out, the motor wont even turn.. im not sure if when you take the other one out the motor still turns or not

 

[bayonnite]

funny that you mention that, cause thats where i went first to test for fuel, and later on (i left the top off) after repacing something, the car would not even crank, i said you gotta be kidding me! now what did i do! then i noticed the starter relay was out, guess i knocked it out while i was working on the ignition, at that point i just had to laugh! but then it was back to buissness. anyway those relays are fine and she just cranks away but w/ no spark. so you said the ecm does control spark? to the point that if the computer fails it will not allow spark at all?? i know it does have somthing to do w/ spark but i do not know to what extent as far as complete spark failure!

 

[clean95]

the ecm does control spark... theres a sensor crank positioning sensor. (cps sensor) if that sensor goes out then there will be no spark! what it does is when u crank over the engine the cps tells hte computer and the computer sends spark then the car starts try that and check codes if u have a code scanner i think autozone rents then good luck check out that sensor tho... mite be the casuse...

 

[95TwinTT]

Does your tach move when cranking? I think that model has a crank sensor and a cam sensor. If the tach is not moving, the ECM is not getting one or both of the pulses.

 

[bsamoul]

any way you can hook up to the obd to see if a code has been thrown?

 

[bayonnite]

just hooked it up and got a p0604 ecm random accesss memory, have no idea what that means, i gotta go catch a ride to work, thanks guys oh, where is that csp sensor are they accessable?

 

[clean95]

crank posistioning sensor is on the front of the engine just behind it looks like the harmonic balancer
in front of the oil pan check there the code i looked it up didnt say much its (ram) idk and the cam sensotr is on to of the engine oin the center... good luck

 

[bsamoul]

yeah, not too much info on that code. altho ram errors are never good, could be the sign of a failing ecu

 

[98hoe]

First thing I would have checked was relay also. Here is some wishful reading. GL

http://www.aa1car.com/library/no_spark.htm

 

[GMCYukalade]

http://www.ncttora.com/fsm/05+/data/ileaf/06toyrm/06toypdf/06rmsrc/rm2006ta/0050042.pdf

Read that PDF.. tells some about it - at the very end of it.. it says Replace ECM

 

[GMCYukalade]

Also figured i'd post this up
http://cgi.ebay.com/ebaymotors/Taho...47229045QQcmdZViewItem?hash=item310047229045&

 

[bayonnite]

ahh man! i wish i would have waited, cause i ordered the ecm from autozone this morning it will be there tomm, 153$ but heres my new concern the ecm says it MUST BE FLASHED FIRST, how do i do this? i am stumped again, i like obd1 you just changed the chip and thats it, the dealer says they need my truck to do it, is that correct? or is there an easier way?

 

[GMCYukalade]

ya, they may need the truck, or one just like it.. basically they have to program the computer to your vehicle.. they should just need the VIN

going with auto-zone was probably a good idea.. because you probably need your vehicle now, not two weeks from now

 

[bayonnite]

98hoe thats a great article, but they never mention the ecm as possible culprit, makes me wonder why not? and 95twintt, the rpm needle does move when i crank it so, i did assume its getting the pulses and sensors are good. so the ecm random access memory code put me over the top into beleiving it to be my ecm behind all this. but yukalade i am still not 100% sure it is the ecm, thats why i am hesitant to tow my ride to the dealer just to find out thats not the problem and then be stuck w/ a dead truck in the dealership no less, thats a lose/lose situation on the money standpoint anyways. i still dont know why they need a physical vehicle anyway?

 

[GMCYukalade]

they should just need the VIN.. every option on the truck is gonna be wraped up in that VIN number

 

[95TwinTT]

I'm still not convinced that the ECM took a dump. Those things are tuff as nails as a rule.

The last 8 digits of your VIN number identify every detail about your particular truck. From that they know what engine and transmission combination along with accessories.

The OBD-2 computers have programs specific to the vehicle. I use after market ECM's in my two hot rods, so I don't know the codes. I do know that the "shop" level of code readers typically offer more information as to what is going on.

I would guess that a dealer has the ability to load a computer with the program needed for your truck. As I mentioned, I'm off into other computers, so I'm a little fuzzy on the procedure.

Good luck and I hope it turns out to be the ECM, since you have a new one coming...

 

[41racing]

They need the truck because the only way to reflash is to hook up to the obd2 connector. I'd be a little scared of the quality of the autozone ecm.

 

[bayonnite]

hey guys, i returned the ecm from autozone, becuase i told a guy at work about my problem and turns out his brother owns a repair shop and he is going to get me one (oem too) and flash it for me for the same price, cool huh! oh and in the meantime, i changed the crankshaft sensor and the camshaft sensor and still a no go. so at least those potential problems should be eliminated for now.

 

[bayonnite]

well finaly got my ecm in today, and problem solved, although it took a while before she turned over, came w/ instructions to "relearn passlock" code and relearn new crank sensor. so it took a while, 3 hours or so but shes running good again, after a week but heck, it was worth it, who knows how much they would have charged me well over a 1000$, and she wasnt done being mad either, after all was said and done. she decides to spring a leak, the radiator has a fracture just below the top oil cooler line (drivers side). well at least i know what the problem is this time, and i can fix it. thanks for all your help guys!