cant get error codes out of ECU

[stocky]

what could be wrong if my car has a constant engine light, but i cant get error codes out of the ECU? diagnostic mode, and scan tools dont do anything. i have tried a couple of different ECUs and memcals

[88GreenVN]

So when you short out the plug the light stays on constant?

Can you get any data at all using a laptop?

[stocky]

yep stays constant. its at an auto elec now and they couldnt get codes out of it with their scanner, or reset the codes

[immortality]

just to clarify, engine check light stays on constant even when shorting diagnostic plug or attaching scan tool? does the same thing even when using another ECU and memcal also?

does the engine start/run? is it stuck in limp home mode?

[stocky]

yeah engine runs. its stuck in limp mode, or bypass mode, at 10 degrees timing. the wire for the ECU to ignition module, the bypass circuit, is supposed to get 5 volts applied to it once the engine is above 400rpm. it gets 0v

[immortality]

faulty dizzy? the ecu would get the RPM's from the dizzy, if it's not recieving a signal it doesn't know it's turning above 400rpm so can't put 5v on output wire maybe. yeah, i think the dizzy is dead (or the module inside the dizzy that is) hve you got access to another dizzy so you can try it?

i think both morton and mack are semi-experts in removing dizzy's with engine in car

[stocky]

dizzy is 2 weeks old. its been going into limp mode on and off, but now it seems to be stuck in it

[immortality]

dizzy is 2 weeks old. its been going into limp mode on and off, but now it seems to be stuck in it

crap. i bet it's a loose wire or something in the plug to the dizzy then. why did you change the dizzy to begin with?

[stocky]

yeah i dunno. i tested the continuity between the dizzy and the ignition module and they were fine. out of ideas

[immortality]

was having a look at the VR V8 wiring diagram http://www.memcals.com/pdf/VRV8%20Wiring%20Diagram.pdf you say the ecu isn't putting out 5v so it seems the ecu isn't recieving a signal from the dizzy. could be a faulty ignition module or a wiring continuity problem between the ignition module - ecu

[stocky]

tried the ignition module on my brother VP 5L and it worked fine. checked continuity between the ignition module and ECU and that was fine too. you can see how annoying this is getting lol

[immortality]

bugger. do yo uhave access to a occiliscope? you need to test the signal at the ecu end

[Cheap6]

Is this with the VP computer or the VR?

[stocky]

both do the same thing

[VrWagz1]

Could be your new dissy has a fault in it as that will form part f the calculations for the est.
Have you metered the actual tps to see if its ok and not open cct or shorted.

[greenfoam]

When things break it's usualy the last thing changed on the car, in this case it's the dizzy. It seems the most likely suspect to me too

[stocky]

foam, work this out. car starts fine with no error light if i put in a VN V6 memcal with knock board, but wont work with any vr tuned memcals

[immortality]

VR HSV would have knock sensor fitted. does your VR memcal have a knockboard? have you changed the tune? does your new tune have the knock board enabled?

[immortality]

any updates? you get this sorted?

[stocky]

yeah got it sorted. made a new v8 memcal, without a socket or anything on it. i dont know why but my car seems to be very picky about memcals. some worked, some didnt, and i never had these problems with my old car. even with my currently working memcal, it would still go into limp mode unless the memcal was pushed in the right way.

what i dont get is, it doesnt explain a lot. it doesnt explain why it would do it after it rained or got cold, why it would do it in the middle of driving somewhere, why it would work fine one day, but when i came back to the car it would go into limp mode. and it never gave me code 51 for PROM error either like it normally would if this happened. oh well, hope it just stays fine for now

[immortality]

i made a adaptor from a header plug so i don't need to socket the memcal. maybe try that instead and see how it goes. you do need a UV eraser however with this setup. atleast you got it running now

[stocky]

yeah i did the same thing, although the adapter i made didnt work too well at times, and the bloody thing has gone missing anyway haha. you got a picture of yours?
i liked the way mine worked, i used a header plug too, but made it in a way that allowed me to use either a 28 pin (VN-VR) memcal, or a 32 pin (VS-VT) memcal

[immortality]

it's a bit rough but'sworking without any problems so far. gotta make a decent one at some stage

[stocky]

yeah mines similar. if you get a longer one with 32 pins, and bend the last 4, it gives you the option of switching between VN-VR and VS memcals

[greenfoam]

Stocky you might need to burn the eproms with some more volts. Sometimes 5 volts isn't enough. I've got a seperate power supply feeding my burner and burn them at 6.5