[2 loud]

Hi i need some help to find out where i shall start to search for this uncommon problem ,,, its a 2000 2 wd astro 4.3 L engine nothing fancy ,,, when i use the turn signal (yepp there are people that know what they are to be used for the engine turns down ,, i i run on staedy speed and turn the turn signal (dosent matter if its left or rigth ) it feel like the engine shuts down but yust in the exact moment as the signal flasches

i looked at the DTC s and il got a bulls eay on all O2 sensors .. all sensors shows DTCs .. il guess this either must be a lack of power to the ecm or ground failure and that the power source or ground are the same for the ecm as the turn signals ??

i have never been up to this before ,,, ths is a friends car as i been repairing and the only electrical as iv been doing before this happend was to swap the MAF sensor ,, but i hade some problems find a working maf sensor and in the search of the fault il cut of the earthcable and ground it directly inte the body abouve the maf ,,, but i dont thing that can have anything to do with this problem ,,, the MAF is real easy to locate faulty of ,,, one ground wire ,,, one postetive and one signal as are messureble thrue a multimeter that reads HZ ,,, before il found a working maf sensor icouldent get any values at all to my PS90 ( OBD II reader ) but with this latest MAF and the grond cable grounded to the chassie all values reads fine on the reader ...

since this aint my car and the old maf was defective and the car dident run on WOT i cant tell if this was even before i changed the maf or if its somethings as has happend afterwords ,,

but the main clue are that the engine shuts down when the turn signal turns on and gets back working as soon as that load get down and that il got a headfull of DTCs from the O2 sensors ,,,, anybody that has any clue where i shall start looking ??

EDIT .... i found out on a scematics tht it seams that the turn signals share the same ground point as the MAF so thats a clue but i cant find any relations between the O2 sensors and the turn signals ,, well i hope this solvs the problem but im still intrested of aditional input if this aint the fault

Åke Of Sweden :ty: :ty:

 

[TurnNburn]

You might have 2 different things going on here. how many miles on the van?

Sounds like a ground problem to me. Can you find that common ground?

 

[WimpTech]

Hey Åke, welcome.

I'm with TnB, sounds a lot like a floating ground. Check your battery terminal and cables for green gunk (corrosion). On the cable, look between the individual strands the best you can. I believe there should be a braided metal line between the engine and firewall. If it looks like this, you got a problem (green corrosion):

If you can use a jumper cable from your neg battery terminal and any exposed metal on your motor, and things start working... you found the problem.

 

[2 loud]

fun fun fun ... hi look who´s back ,,, i did connected back the old oem black ground wire to the maf once again and did even connect an additional ground cable at the same spot as the maf as concted to earlyer ( the firewall behind the maf),, did even tigthen the bolt nutt behond the battery so now im back to stock oem exept for that extra ground wire ,,, and the result ??? yihaaa it works ,,, no reaction at all when il use the turn signals any moore ( wait for it ......... ) BUT ( of course )

not it throws P0102 ´s lov voltage from the MAF ,,, and once gain no reaction at all when i look in the reader ,,, both the value frpm the MAF and the frequency are zero !! !! this ameze me ,, the truck runs good with 14/7 and this scenario are ecatly the same as before il changed the maf sensor ( but that sensor was fysicly damamge so i was needed to be swaped anyhow ) ,,, this MAF sensor are a real easy peice o examinate ,, one wire (black) to solid ground) ,,, one pink wire as shall have 12 v + and finaly the yellow wire that shall react widly when you messure HZ when the engine is running and you shift rpms ,, .. i thinking about swap all these three wires out complettly to avoid any damage inside of them as shifts in resistance while it shakes and rattles while you drive ,, ,, il guess i will find the ecm in front of the passengers foot space or behind the driver side inside the wall ( this is a HITOP model ebuild by some of al those rebuild shops ,, dont remember who but il guess i wont matter ,,, so if could get som help to point out what cables thats are involved (coulors and pinnouts) ,,, and here i got a ball in my throth ,,, or does the ecm live outside in the engine compartment behind the battery ? ,, those use to be quite ugly of corrotion ,, and if i dont remeber wrong GM hade some problems with those ecms in the engine compartment when the bolts that keeps it together pop the heads off and let moistrue inside the ecm ? ,,

my thougths goes in the way that somewhere these oem cables are damaged and when the ground as now are perfect" the voltage goes down in earth and the messured voltage at the ecm are as low so the P0102 comes ,,, in fact il guess its that dtc you recive even with zero signal ,,, so that can be away ,,, when il cut the oem grond wire away the signal from the new maf are as strong as i dont get as disturbed as i does when the ground are better ( earlyer i ´l cut it totaly of from the maf and grounded it above the mafsensor so then the oem harnesst dident connect to the maf at al and this is ONLY the ground (black) wire boot other (yellow and pink) are still untouched so theres my bast conspirtion at this moment ,,, so what happends when the SIGNAL (yellow) goes into ground ? il guess it simply dont deliver ? its a ac signal ,, shoud it been the pink wire as got 12v + hoppfuly the fuse will blown or the harness gets real hot and burned ,, but thats not any signs of

so tommorows mission will be to find out where the ecm lives and hoppfully even found out the positions of the pins /wires as needs to be swaped ,, ,,, but another thougth is a defective ecm ,,, is theres any surten ways to tell when its the ecm tht has gone bad without any dtcs ? that earlyer situation as this question started with sounded alot as a ground ischuee and if the ecm gets moitsrue and corrosion inside ,, theres the same results ,, i spimply love these kind of faults ,, they are really educationg ,, ( i usally works alot with electrics so im not all new to this ) but sadly it shoud have been so mutch easy to understund why these faults apper if i shoud have time to st down for some time and study how these elecrical systems woks around these engines ,, but that tie seams never to come ,, i learn moore and moore by each any every fault il work with ,, but these GM systems are not hard to understund so its not rocketsience ,, the only thing i migth have against GM is the quality they used on the harnessts ,,, they are often the main problem

and earlyer il got the que how loog this car had on the meter ,, il think its less then 20 k europian miles

btw is theres a passlock ii system on this truck ( 2000 ) ?? (il think if i needs to swap the ecm ,, is theres some slick way to pass the passlock ? ) "normaly" when you gets a deigned software you can tell the programmer so exclude the passlock but that not an option if i shall get a used ecm from ebay ,, ,, normaly you get thrue passlock by solder in exacl resistors but then i need to know what value the new ecm would ask for ?

hehe this seams to be a never ending story ... i ust wanna get this once up n running ,, il got a moore intressting 262 V6 project upcomming ,, for my wifes S10 blazer 2002 i am expection a new spider ( 36# lbs) and a customs build ecm from brian at pcm for less ,, a custom grinded camshaft and a set of rebuild cylinderheads build by my freind chad golen at golen engine service in NH ,, those are rebuild and got larger valves and some grinding also in the same shipment there are a set of headers for the truck ,, so i am expection to get a final hp around 300 hp

 

[TurnNburn]

At least you have the ground problem tracked down to a certain location and fixed.

Since you said it was so easy to diagnose, what are your measurement on those wires you mentioned for the MAF? Does the van run while throwing that code? Did you unhook the MAF while cleaning or tinkering? What I am getting at is was key turned to the ON position while the MAF was disconnected at any time. Cause that would throw that code and still run after you plugged it back in.

 

[chevymaher]

Here is a video for testing and finding out which wire is which.

 

[WimpTech]

Åke- I love your enthusiasm but you would do well to dial it back a bit and be patient. If you start poking around the ECM and wire harnesses, you are more likely to cause problems than find them. If there is an intermittent issue, then you don't want to keep adding variables by poking around and changing other things. Just one step at a time. I was surprised that you clipped off a wire to the MAF? I would never suggest doing anything like that, really bad idea mate.. I hope I just misread that.
Black is ground, which grounds through the electrical system and indirectly to the battery, so the bad strap won't affect that. Pink is 12v supply, sounds like that is OK. Yellow is the MAF signal that the ECM inturperts into air flow readings. A lack of AC signal on yellow will trip P0102. To test, remove the connector/ wires. Use a volt meter set to AC volts and place the leads between where black and yellow went. With engine running, vary the throttle to see if you get a reading. If so, MAF is good, look up stream. If not, replace MAF.

what code scanner are you using? I'm with TnB again here, clear the code and keep driving.

 

[WimpTech]

Randy beat me to it! haha awesome my friend.

 

[2 loud]

well use a PS 90 scanner and no i diden hook off the conncector ,, even when i am driving i can erase the code oand it keeps cooming back ,, i cant get any messurments to my reader from any MAF activity ,,, i also got an old auto xray .. results are the same there no grams indicatied from the maf and the P0102 codes comes back time after time

and i cant see why it shoud be so catastrofick to cyt the ground wire ,, according to the scematiccs its a single wire that attaches to the water outlets housing ,, yust that wire ,, dont get togheter withanyone else ,, well its solvd back again and with that extra grouhnd direct from the chassie

 

[Leeann_93]

If you need more, let me know.

 

[2 loud]

Hi needs to bring this once up again ,,,, iv changed the wires to the MAF and even the maf ,, it has been working good but not il got the amazing yellow ligth again ,, so il conneced the scanner and look what signals it shows and once again it the maf signal and it tells me low performance ,, and on operational dats is shows 0.00 g from the maf ,,, il messured the MAF for frequensies and even power in and earth ,, all seams working good from the maf ,, all powers ( posetive and earth) are in place and the frequensy changes by the rpm ,, so now it looks like the ECU are next to swap ,, the signal from the MAF goes straigth down to the ecu and somethings inside are corrupt ,, the signals i can read out of the OBDII connector must come from the ecu since the maf signal only goes to the ecu ,, so il guess i need to find a new ecu for this van ,, is theres anything special i shall look out fore ,, what numbers of ECU is the rigth for this one ? yes i know i can propebly read out of the chassie of it but is theres maybe some upgraded version aviable to look out for ? ,, the connectors are all fine and not any corrosion on the pinns either and since the readings in operational mode tells me the signal from the maf are dead its only the ecu left to change or am i missing something ?

 

[WimpTech]

Might try tracing the wire and connection to the ECU before going that route. As I understand... One cannot simply swap the ECU like a radio or seat, it has to be reprogrammed for your vehicle which requires a GM TECH II tool or similar and is usually pricey.

 

[2 loud]

been threre done that ,, and i have made a siple reroute of the wires ,, and the only wire that connects to the ecm are the signal ,, earth is straigth to the chassie and the posetive wire is connected straigth to posetive .. il got an Tech II unit but have never changed any software so i would rather dont do it ,, but iv seen at ebay sellers that tells they deliver ready ecu with the rigth software for the car ,, but since these vehicles are "same same" in my eays i would guess the software are the same in these cars if il find a 2000 ecu il would belive its programed to work even in this car or ? as loong as its got the same engine and transmission and are 2 wd ?? this once are a hitop with lots of luxery inside ,, a factory rebuild model(dont know of who rigth now but il can find out ) but iv never seen anyone made any changes to the drive train ?

 

[WimpTech]

I'm sorry, I am not an expert, but we know people who are! I'm sure Will can chime in shortly.

So... you get an AC signal at the appropriate wire on the MAF, but the ECU shows no signal?

 

[2 loud]

correct theres are simple ways to messure the MAF to enshore it works as it shoud and it send out the right kind of HZ but in the scanner it tells ZERO signal from the maf so the DTC shows low performance from the MAF ,, ,, the maf works so it cant be anything else then the ecu in my eays

the already programmed ecus are like this one
http://www.ebay.com/itm/1999-GMC-Yukon- ... uw&vxp=mtr

 

[AstroWill]

MAF is working, wiring is electrically good, then the last thing is the PCM.

 

[staticj123]

been threre done that ,, and i have made a siple reroute of the wires ,, and the only wire that connects to the ecm are the signal ,, earth is straigth to the chassie and the posetive wire is connected straigth to posetive .. il got an Tech II unit but have never changed any software so i would rather dont do it ,, but iv seen at ebay sellers that tells they deliver ready ecu with the rigth software for the car ,, but since these vehicles are "same same" in my eays i would guess the software are the same in these cars if il find a 2000 ecu il would belive its programed to work even in this car or ? as loong as its got the same engine and transmission and are 2 wd ?? this once are a hitop with lots of luxery inside ,, a factory rebuild model(dont know of who rigth now but il can find out ) but iv never seen anyone made any changes to the drive train ?



could tell me what wires to pcm are earth ground oem harness black wire or tan white ?