ABY Factory Immobiliser Advice

[oollit]

Hi,
I am having problems with a non starting ABY S2 and after ruling out most of the common mechanical failures I am starting to look into the immobiliser.

Would the factory immobiliser prevent the fuel injectors from activating and prevent start up, or would it start for a few seconds and then stop?
The iimmobiliser warning light on the dashboard comes on for a few seconds when the ignition is turned on and then goes out, and does not flash when I try to start the car.

The origonal problem was non starting, but after being connected to a heavy duty battery charger with a boost function it started popping fuse 27 and had no spark or fuel pump activation on cranking.
I have tried a non immobiliser ECU which stopped the fuse popping and restored the spark and fuel pump activation but the fuel injectors are not opening.
I then got the D900 and D901 diodes replaced in the origonal ECU, which has also stopped fuse 27 popping restored spark and fuel pump activation, but I still have no fuel injector activation. I have 12v at the injectors and checked the restance and they all are in spec.

I have also replaced the cam and crank sensors and checked the timing pin on the flywheel, so have ruled out most of the common mechanical failures.
The earth and power feeds to the ECU all seem to be ok too.

I see there is a module under the dashboard, is there any way to test/bypass this or would I need to buy a 2nd hand module and key to test if this was faulty?

[B5NUT]

That immobiliser looks to be for the Coupe & A6 models, and if it acts the same way as the A4 B5 immobiliser of a similar year, then the engine is allowed to start then cuts out a second later with the immobiliser light flashing. Many years ago I had a bad pickup coil on my A4 B5 which caused the engine to start then cut out immediately, but I did get the flashing immobiliser light on the dash.

No idea on how to bypass the immobiliser

[newsh]

Best way to get rid of the immobiliser is to fit a non immob chipset in the ECU.

OTOH. Have you checked the timing carefully? If the bottom pulley has broken it’s keyway and moved the car won’t start. Align the zero mark in the bell housing window and check the cams are on their marks.

[Mikes2]

Normally the car will cut out after a couple of seconds for an immobiliser fault. Is there any codes on the ecu ? Timing needs to be perfect at 0 degrees static.

[varia]

immo in the S2 ABY (RS2) is on 2 relays (small, maybe red/burgundy/brown and green if i remember correctly)

edit: added pic

[oollit]

I checked the timing before and after I fitted the new cam position sensor and I am fairly certain that it is ok, but I will double check it to be 100% certain that it is good.
The car will fire up with a little bit of carb cleaner in the throttle body, and the plugs are bone dry everythime I check them so fairly sure it is down to something preventing the injectors from opening.

[newsh]

Doesn’t sound like the immob.

If the TDC sensor signal doesn’t arrive in the middle of the cam shaft window signal then the injectors won’t fire.

When checking timing don’t use the marks on the bottom pulley, use the zero mark on the flywheel through the bell housing window.

Also check your grounds on the side of the inlet manifold.

And the fuel pump relay

[oollit]

Yes it looking like the immob isn't the problem after all otherwise it would fire for a few seconds
.
I did use the flywheel marks when I fitted the cam position sensor, but I will be double checking that when I get a chance.

I have already checked the earth connections on the inlet manifold for corrosion and they were fine, and I have continuity from pin 14 and 19 with my power probe, and according to UrS4boy's ABY/ADU pin out post, they are the pins that go to the inlet manifold.

Fuel pump relay was the first thing to be replaced.

Probably worth checking the new crank sensors too, had bad ones in the past so it does happen

[vidar skotheim]

Mount old cranck sensors ..

[oollit]

Got another look at the S2 today, engine timing looks spot on and refitted the old crankshaft sensors and it still will not fire up.

Checked continuity from pins 47 and 48 from the ECU to the crankshaft position sensor and pin 8 to the camshaft position sensor and all look fine.

I also removed the earth point studs from the inlet manifold, but there was no corrosion, even running my test leads from the inlet manifold to the negative battery terminal made no differance.

Tested one of the injectors by grounding it with my test probe and it clicks fine, so don't think it is an actual injector problem, but the injectors are not firing when I try to start it.

Still can't connect to the ECU with my code readers, even with a new lead.

Really strarting to run out idea's now.....

[Tractor Dave]

Have you tried another ecu?

[Ian Simmonds]

Still can't connect to the ECU with my code readers, even with a new lead.

Really strarting to run out idea's now.....

The MTM ECU we’ve got here has had the code reader facility disabled (we’re convinced of it) as it stubbornly refuses to offer up codes using multiple pieces of equipment and ECU reading trickery.

[oollit]

I have tried a non imob ECU, and the symptoms are exactly the same. Fuel pump activation and spark, but fuel injectors not firing.

I have had 5 different code readers, and 2 different adaptor leads and still can't connect to either ECU. Not just cheap code readers either, as I have an Autel Maxidas 708 and a Foxwell NT680 Pro.

[Bowie69]

Next wires to test continuity for will be the injector earths -the ECU switches the earth as I understand it, so potentially damage there will give a no-run situation.

Find the right pin on the ECU and ground it with ignition on, and you should hear injectors fire.

[oollit]

I have the pin outs for them ready to go for the next chance I get to look at the car.


16/55 - Output control signal to Fuel Injector No. 5 - N83 – BR/R
17/55- Output control signal to Fuel Injector No. 2 - N31 – BR/BL
34/55 - Output control signal to Fuel Injector No. 3 - N32 – BR/G
35/55 - Output control signal to Fuel Injector No. 4 - N33 - BR/W
36/55 - Output control signal to Fuel Injector No. 1 - N30 – BR/BK