# no start condition, no ecu communication?



## dudeman08 (Feb 23, 2009)

as you have already read in the title, my car wont start. :banghead: 1998 jetta mk3 2.0 5spd. when i put the key in the on posistion, i dont get the check engine light like youre supposed to. the bulb didnt burn out, i know this for a fact and it come back on ever once in a thousand tries. whenever the CEL isnt on it wont start and whenever it is on it will start. sometimes when it does start it runs rough, others its pretty normal. i tried to put my scanner on it when the CEL was out but it kept coming up with a comm error and when it is on, i get no sort of codes or anything. any ideas? it didnt start happening untill i started banging out my sound deadener from the floor and under the dash. i cleaned my battery posts and cables and the ground to the trans and starter connections. startin to get frustrated. any help would be nice. thanks in advance.


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## greyhare (Dec 24, 2003)

Check relay #3. It should have a 30, 109, or 288 on it.

Relays are numbered as follows:

19 20 21 22 23 24
13 14 15 16 17 18
1 2 3 4 5 6
7 8 9 10 11 12
>


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## dudeman08 (Feb 23, 2009)

what is it id be looking for?


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## dudeman08 (Feb 23, 2009)

you know what, i do remember bumping my arm up against the fuse block and other things under there. ill check to make sure its seated properly tomorrow. ill let ya know whats what. thanks.


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## volkswhisperer (Sep 25, 2006)

Pull it out and plug it back in. It's the ECM power relay. You should hear/feel it click


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## dudeman08 (Feb 23, 2009)

yo, weird as hell. i just checked and i dont thave that relay. just for s&g, i put the key in the on posistion and the CEL came back on. wtf? what should i do? i know this will keep happening.


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## dudeman08 (Feb 23, 2009)

lookin around on different parts sites, the only cars that use it are up to mid 1996. i guess mine is spposed to be like that? what other possible cause for this?


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## greyhare (Dec 24, 2003)

Based on your original post; you knocked something loose while removing the sound insulation.

Get under the dash and check for loose electrical connectors.


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## dudeman08 (Feb 23, 2009)

any possible ideas what it could be? i was using a hammer and a chisel to break up the tar sound deadener from the floor and uner the dash. could the vibration alone have caused something to happen? i think i lost a ground somewhere, just not surewhat to or what not. im about to take everything out of the fuse/relay block and plug them back in one by one to see if that helps. i even unplugged and reconnected my ecu yesterday and that didnt work. i was doin some reading in my bentley manual earlier today with the wiring diagrams and i think that its go something to do with ground number 137, where ever that is. bentley says its a ground connection in the motronic mfi wiring harness. any ideas where that could be located?


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## dudeman08 (Feb 23, 2009)

also, yesterday in my attempt to fnd something knocked loose, i tapped my arm against the wiper stalk on the column and the wipers went up but didnt come back down.


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## volkswhisperer (Sep 25, 2006)

dudeman08 said:


> also, yesterday in my attempt to fnd something knocked loose, i tapped my arm against the wiper stalk on the column and the wipers went up but didnt come back down.


How is your relay #8
It's the intermittent wiper relay


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## dudeman08 (Feb 23, 2009)

well, i fixed the issue with the wiper. stupid me, i started doin some body work and deleted the fender mounted antenna but i tucked it under the cowl and the arms for the windshield wiers got it caught in the middle. thats fine now. i dropped my fuse/relay box and nothing seems loose. i resecured all the relays and what not. next step is to disconnect and reconnect everything on the back of it. any other ideas of what to do?


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## dudeman08 (Feb 23, 2009)

bump.


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## dudeman08 (Feb 23, 2009)

bringing this back from the dead since i just got some time to work on the car after doing the heater core and swaping the dash. i did some trouble shooting 2 days ago and this is what ive come to thus far:

battery voltage: 12.1

ignition switch is ok, it gets power and does all of its functions. (on, acc, and "start" position all have power. cranks like a champ and everything on the instrument cluster works, minus the cel lighting up like it should.)

ignition coil: recieves the 12.1 volts the battery is putting out.

voltage at the fuel pump fuse: 0.4 volts, i assume this is the refference voltage. (correct me if im wrong and give me specs please.)

Fuel pump relay is gettin no power with the key in the on position and of course, you cant hear it. (had my dad listen through a pry bar against the filler neck.)

fuses 15 (engine electronics) and 18 (fuel pump, heated o2 sensors) are ok. havnt checked the power to them yet.

can anyone else think of anything else to check? im going out to do more trouble shooting once the weather clears up a bit. everything is plugged in on the relay/fuse panel, aside from some free hanging plugs from the harness in that area, which i assume are for optional equipment that wasnt in the car. (i know that many car companies make 1 harness and install it in all cars whether or no they came with certain things to save money and leave the ones that arent in use dangle there in the mess of wires.)

all help is greatly appreciated.

:banghead::banghead::banghead::banghead::banghead:


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## greyhare (Dec 24, 2003)

Do you have a Bentley manual? If so you need to look at schematic 97-388.

You are not getting 12v at fuse 18? (Fuel pump fuse)

You are getting 12v at the coil? Fuel pump relay control power and coil power are both buss 15. (switched 12v.)

The ECU turns on the pump relay by controlling the ground.

No power at F18 means:

A; pump relay is bad
B; no control signal from ECU
C; wiring fault

Have you scanned for codes?

Pull relay 12 (fuel pump)
Check for 12v at terminal 8/30 (This is bus 30 B+; the relay switches this for the pump.)
Check for 12v at terminal 2/88 (This is bus 15; should have 12v with key on.)


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## dudeman08 (Feb 23, 2009)

yes sir, i do have a bentley manual.


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## dudeman08 (Feb 23, 2009)

ok, im looking at that schematic now. ill have to out to the car and take a look. could the relay being bad cause the cel not to light up?

also, i cant check for any codes because the ecu isnt communicating with anything.


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## dudeman08 (Feb 23, 2009)

ok, i just went out and checked again. im only gettin 0.4 volts still at fuse 18 for the fuel pump. (yellow 20 amp) i also checked the fuse 15 (engine electronics) for voltage and it was 12 volts.


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## dudeman08 (Feb 23, 2009)

i just checked the voltage on t-30 for the f/p relay and got 12v there as well. any ideas what to check next?


also, i just noticed that the relay is a little discolored on one side. its the origional one. the relay is gray in color, but one section has a light brown hue to it. could it be burned out?


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## dudeman08 (Feb 23, 2009)

thanks for the help so far, btw. :thumbup: i atleast now have a direction to run in.  just got back in from doing some more trouble shooting. since the last update earlier, ive covered a lot of ground. 

fuel pump fuse (#18): still only 0.4 volts

engine electronics fuse (#15): 12 volts

terminal 30 for fuel pump relay: 12 volts

checked fuel pump relay terminals 30 & 87 (as per what bentley said) and got 12 volts.

i disconected the ecu and checked for the constant voltage to it ( T-1 (-) & T-54 (+)): 12 volts

i also hardwired the fuel pump to check and see if it opereates and it was good. primed for the 3 seconds that it normaly does.

what should i do next?


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## greyhare (Dec 24, 2003)

Do you have 12v at ECU pin 23 with the key on?


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## dudeman08 (Feb 23, 2009)

im not sure. i didnt check that one. ill go out in a few minutes and check it out.


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## dudeman08 (Feb 23, 2009)

yes sir, i did get power at terminal 23. got the 12 volts that the battery is putting out.


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## dudeman08 (Feb 23, 2009)

happy fathers day bump! :beer::thumbup:


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## greyhare (Dec 24, 2003)

Does the CEL turn on at initial key on?

No ECU communication, continuous power to ECU, switched power to ECU. I hate to say it but you may have a DOA ECU.


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## dudeman08 (Feb 23, 2009)

the CEL doesnt turn on at the initial turn in the on position. its sorta a sporadic event. sometimes the CEL would pop on, very rare this happend but it ran great when it came on. it hasnt come back on though for a while. could it be the fuel pump relay being bad? i took the cover off it and saw that there was a nice little black burn mark on the inside of the cover. :screwy: :banghead:


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## greyhare (Dec 24, 2003)

The relay sounds like it got hot, so it should be replaced. The relay should not affect the CEL or communications.

Try replacing the relay but I doubt that is the core issue.


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## dudeman08 (Feb 23, 2009)

ok. im gonna order up a new one when i get paid this week. i guess i should check and see if anyone has an ecu for my car on here as well, just in case. i also wonder if my chip came loose in the socket in the ecu because i have solid motor mounts and wonder if the vibration had anything to do with it. ill pull my ecu later today and take it apart to check.


btw, thanks for all the help so far man. if you were close to me id get ya a beer. haha. this will have to do though. :beer::beer::beer::thumbup:


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## dudeman08 (Feb 23, 2009)

i went to the junk yard today and "liberated" a fuel pump relay from a 97 jetta gt and still no luck. i also took the ecu apart and didnt see and burn marks or smell anything burnt. :screwy: im stumped. i dont get it. my dad said that the ecu could be fried and i wouldnt know it if it was a bad resistor or diode. i dont see anything wrong on the surface of the circuit board, maybe there is something bad beneath the surface of something on the board. uhhg.... :banghead::banghead::banghead:


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## dudeman08 (Feb 23, 2009)

havnt had much time to try to fgure this out. been busy with work and other things. put in a brand new fuel pump relay because i needed one anyway and that didnt work. can anyone help me out by telling me where all the grounds are located that go to the ecu? im almost positive its a ground issue. dont want to jump on the ecu as being bad just yet. also, if the ecu was fried, would that mean my c2 chip is done too?


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## dudeman08 (Feb 23, 2009)

bump :wave:


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## wicked2.0 (Nov 18, 2002)

I'm having the same issue except my cel doesn't come on at all. I've replaced the ecu and relay, checked fuses, checked coil and fuel pump, checked grounds and powers at ecu harness, checked ignition switch, and still cannot figure out what the problem is! I'm getting very frustrated. I have no fuel, spark, or communication with the ecu. I'm also thinking it may be a wiring/ground issue because I'm running out of things to replace/check. Anyone who knows how to fix this issue, PLEASE let us know!


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## RADsoc014 (Jan 14, 2003)

exact same issue i'm having currently in my 2000 2.0L aeg motor....... car runs whenever it feels like..... meaning when i turn the key on and the CEL light comes on the car runs..... keep updating as i will let you know how mine is doing too. i'm gonna use a scope and see how all the modules are communcation and that today


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## RADsoc014 (Jan 14, 2003)

finally got to the end of this problem, new ecu and have VW reprogram the immobilizer and you will be go to go............. Memory in the old ecu kept failing


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## WvS4 (Apr 22, 2011)

bump:banghead:


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## dudeman08 (Feb 23, 2009)

i was only able to get fuel when i hardwired my pump, and i hadnt had the chance to check for spark yet. my guess is im not getting that, even though the coil gets power, the module to fire it is controled by the ecu. im trying to get another ecu but no luck thus far. will keep posted. :banghead:


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## dudeman08 (Feb 23, 2009)

well, i found out the issue for my ecu. my c2 chip did a memory dump. i plug the stock chip in and she started right up, it was a little rough because of the stock tune with all the work thats been done, but it started none the less. i guess i gotta call c2 or bfi about their chip being a piece of crap and get them to give me a new one. its the $200 stage 2 PEM.


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## x7thxmiltown (Apr 11, 2011)

try cleaning the bulkhead connector if that dosent work for others that havnt figured it out


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## jeffpepin (Apr 12, 2015)

hi have exactly the same problem , car is inoperative !! 2.0l aeg , no check engine light when key is turned to on position ,,

i would like to figure how CAN-HI CAN- LOW communication work on theses vehicules 

mine is a mk4 platform jetta with 2,0l AEG engine , this problem should affect all mk4 plateform i think , 

i have benchtested all my 3 ecu , all working perfectly i have succefully read /erease codes , but when i connect theses ecu on the car , still no check engine when key is on , all other things is working , car crank like a charm , but still no injection

im lost i want to study K-line , CAN line and ''w-line'' , on mk4 plateform , and hardwire these wire to see if it will solve my problem 
information is very confused , people said looking for 109 relay but 109 relay only exist on tdi? because i dont have this 109 relay is like a 100 relay and it is obviously not in the same place that schematic accord 

i have doublechecked all fuses , all relays , 
hardwired vcc directly to car battery to eliminate the NO POWER TO ECU HYPHOTESIS..i dont know if a K-line can provoke a non-start condition because people seem to say that k-line only affect the diagnostic part of the car and not the Running mode ... this is terrible haw its confuse me , and im very frustrated because im obligated to run in ''pontiac montana '' ,, just too bad


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## jeffpepin (Apr 12, 2015)

the worst thing in all that is not really the electric trouble ,, but the PONTIAC MONTANA :facepalm:


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