can a faulty sensor stop the engine cranking over

john2666

Is it possible for a faulty, knock sensor or temperature, oil level/pressure etc to tell the ecu not to start the engine ? i mean even stop it cranking over, i have put a vectra b z22se into a veccy c which had a z22se engine, i had to change things like inlet manifold and some other stuff but i never changed any of the sensors i kept the ones off the veccy b engine, as i used the veccy c ECU etc would this cause a problem// does anyone have any advice
thanks guys

MikeS

on the newer vauxhalls some of the sensors are coded to the ecu however i am no way sure it applies to this ecu

is the ecu light coming on when u switch on the ignition ?

BURT150

Might be a stupid question cus i dont know what youve tried already but dose the engine turn by hand?

john2666

hi Mike,
yes it turns freely and i have out power to the starter and it turns over great, all i am getting is a click from the relay in the passenger wheelwell but the ecu light isnt coming on even when i turn the ignition on and when i plug the odb diagnostics unit in it wont see the ecu it just tells me it cannot establish a link, i am at my wits end with it i have changed every relay checked every fuse checked all connections ........ it is only a 52 plate vectra

MikeS

wonder if it is the immobilizer

are you getting fuel pressure with ignition on ?

unplug the plastic cap on the fuel rail and it should look like a normal tyre valve

so check for fuel, put a thin screwdriver in the valve and it should squirt out about a foot, watch your eyes

then check for spark, just pull out the coil pack and turn it on it's side and get someone to turn her over and look for spark, u might need to earth it though

and get back to us

i am thinking it could be the crank sensor or the earth points around it as i know there is shit loads of earth points on the lower engine loom

also unplug the connectors for the ecu and check there is no bent pins

john2666

Hi Mike ther is fuel coming up to the fuel rail and it is strong, i cant test for spark as the engine wont crank over on the key, i have wondered about the crank sensor, could i put another one on it from another engine i have, i know this other one works, its strange that is was running fine for an hour then cut out, the rumbling noise it made jsut before it cut out made me think crank sensor but i didnt think this would cause the ecu not to be recognised by the odb reader

MikeS

so your saying she wont turn over now either

sounds very odd

looks like volt meter job on the alternator could well be the alternator is wired up wrong though m8

an immobilizer would stop the engine from turning over though

john2666

If the immobilser had gone faulty would i get a warning light on the dash, i thought it would only stop it firing and it would still turn over, when it originally cut out it would not even crank ater that

MikeS

depends on the alarm

i had a toad alarm that cut off the starter motor and fuel pump

like i said i am not sure about the vectra C

might be worth asking on their site about what u have done

the scary thing is that she worked for a while now she doesn't

what u can do is bypass the alternator and run some jump leads directly to the starter motor from the battery to rule out the starter motor

john2666

Hi Mike i have done that and starter motor turns the engine over when i give it a direct feed, it just wont fire.......

Daz

If you have 12v feed at the starter main terminal,check the signal wire has 12v there also when the key is in the start posostion......also check the engine earths as if the engine earth is off it prob wont crank

If the immobilsiser is the vx one and a faulty, the eml will flash...the crank sensor being faulty wont stop it turning over,it just wont start...

john2666

Hi Daz, the EML light wont illuminate at all, even when the ignition is just turned on and the ODB reader wont establish a link as though it cant see the ECU, i have changed the crank/knock sensor and every other sensor on the block, no difference. the immobiliser is standard vx if this were faulty would it stop it cranking?

MikeS

if the eml aint on then it is either an engine bay relay, ecu relay, bad earth or a fubar ECU

unplug the ecu and check the connectors and pins then check earth points and loom

Daz

I'd be checking all the earths,make sure u got the one on the ecu too

john2666

hi guys, its looking like the ecu as the relays and fuses are working fine i have checked them all, it cant be an earth wire because the car was running smoothly then just cut out, i have checked earth connections but i suppose one of the earcths could be damage internally i have supplied additional earths using jump leads but no change

MikeS

sounds like u need a mobile auto electrician

vocky

on the vectra B there are hidden fuses, I suspect the vec C possibly has the same, it does appear a fuse has blown somewhere 🙁

Daz

Just out of interest,have acheck around by the battery,and just under the tray itself,as recently in work we had vauxhall corsa in for the same fault(was running then stopped and wudnt go again and had no eml)
There was a corroded earth wire which goes to the ecu just under the battery tray, gotta be worth alook...

john2666

Thanks Daz i am gonna check it now, would be great if it turns out that easy.lol ni will come back shortly
I have had the whole bottom of the dash out looking for hidden fuses, there are 3 main fuse boxes in the vec c, one under bonnet one in the boot and one near the passenger footwell.... god why all the bloody electrics