1997 V70 EU immobilizer test, no start

oldvolvos · Post by **oldvolvos** » 28 Nov 2020, 10:30

Hi
I have a start problem with my 1997 V70 (engine B5254S, 125 kW). It starts up, then dies down after a second, quite suddenly. If I take out the fuel relay, it runs for like five seconds, then fizzles out. If I bypass the relay and make the fuel pump run continuously, no effect. I have swapped the fuel relay with that of another car, no effect.
I have replaced all the ignition parts (the plugs were rather dirty), no effect. I get a spark that looks OK, but the car just dies anyway.
There is pressure in the fuel injection rail, and when I took it out and turned the engine I could see small drops being ejected from the rail, so it looks OK.
I have checked the vacuum pipes and replaced one, no difference.
The engine does not react to starting gas.

I now suspect the immobilizer unit.
I have tried exchanging the antenna ring for that of the other car, but then none of them starts. I therefore suspect that the antenna ring and the immobilizer box need to go together (although some people say the ring is not specific to the key or immo unit).
I then thought I could take the immo unit from the working car and put it in the non-starting one, with the ring and the key from the other car (the key fits, so I do not need to change the lock).
In this way I can test whether it is the immo unit which is faulty.

Is there any flaw to this plan? Can I ruin something? Is there an easier way to test the immo unit for faults? I do not have a reader for the fault codes, got to get one I suppose, but not right now.
When I had tested the ring from the faulty car in the working one I had some trouble starting it later on, when I had put back the original one. It runs now, but that was a bit scary.

Is there anything else I need to test?

Post by **misha** » 28 Nov 2020, 17:33

Up to '99....you need to pair a key(chipped key) with immo box....but....you need immo box from s,v,c,xc70 up to '99 before CAN protocol kicked in.
You can't use a chipped key and immo box from '96 & '97 850.
Immo boxes are a bit different.

Start & run and dying after exactly a second...is immobiliser issue.

They rarely fail...usually a key(chipped key) is more common problem.

Azik09 · Post by **Azik09** » 29 Nov 2020, 10:33

I have tried exchanging the antenna ring for that of the other car, but then none of them starts.

There are 2 types of antennas at least. With same dimensions and connectors, but different resistance. Maybe that's why another car didn't start with your antenna. Or your antenna is damaged. Check resistance of both coils with ohmmeter.

oldvolvos · Post by **oldvolvos** » 29 Nov 2020, 12:48

OK, good advice, thanks.
The other car with which I am testing is a-99 V70, same engine, but automatic, so should be OK then.
I did notice that the antennas had different numbers on them. I'll check the resistence.
We have two chipped keys to the faulty car, and none of them works, so probably not the key which is at fault.
I will also call the local mechanic and ask how much it would cost to remove the immo box. We don't need that where we live.

xanthefin · Post by **xanthefin** » 29 Nov 2020, 13:21

When you turn the ignition on there is communication between Motronic ECU and IMMO. If check live data of immo there is status message of this and antenna (and chip was it registered to IMMO). I can't sorry give blindly any advice to fix issue.

Post by **misha** » 29 Nov 2020, 14:22

You can't use immo hardware from '99+,i allready told you that...because of CAN protocol which '99+ cars use.

Also...you can't use immo hardware from '97-'99 in '99+.

You need immo box and paired chipped key with that box from '97 s,v,c,xc70 UP TO '99 for your '97.

If antenna ring is bad...you also need one for cars UP TO '99.

You also CAN'T remove it because the ECU will look for it's OK signal to start the car.

You will need a good tuner who will be able to remove IMMO function from software with high-end equipment.

Azik09 · Post by **Azik09** » 30 Nov 2020, 00:27

Try to disassemble antenna and solder wire to pins connections

: IMG_20201130_100922.jpg (152.26 KiB) Viewed 1581 times

: IMG_20201130_100902.jpg (142.23 KiB) Viewed 1581 times

Code reader would be very useful...

Post by **abscate** » 01 Dec 2020, 04:55

These antennae rarely fail. They are just a piece of wire. The start -run -stall cycle is indicating the key isn’t being recognized as correct by the immobilizer. The best option Is to use Vida to confirm this , you will then need a subscription to program the keys

oldvolvos · Post by **oldvolvos** » 01 Dec 2020, 05:26

Thanks for all the advice everyone, I have learned a lot about the immo system now.
However, something funny happened. I talked to my local mechanic, and he thought it unlikely that the immo was the issue (as did some of you in this forum) and thought it might be a fuel problem. I then started thinking about the curious effect of the car running longer when the fuel relay was disconnected and did a test.
I removed the fuel relay and connected a wire to the positive pin in the relay, so I could make the fuel pump run whenever I touched the other end to the battery pole. Thereafter I started the car, got out and touched the battery pole with the wire for a second and removed it again. Repeating this whenever the engine faultered I could keep it running.
Apparently, there is nothing wrong with the immo system, the fault is in the fuel injection. Apparently it gets too much fuel.
So, I will order an error code reader and start checking the fuel rail more thoroughly.

So, thanks for the help. I think its better to end this thread here, and I'll start a new one for the fuel problem when I have done some work on it. If I solve it I will post that.
cheers

Post by **abscate** » 01 Dec 2020, 05:33

You can use this thread, we can change the title as it changes !,

The fuel relay removal behaviour had me puzzled too. The 1999 relays seem to last longer than the -1998 version , too.

The 1997 version can fail many ways, intermittently, cold temp, hot temp