Starting/Immobiliser Fault

[stephen31]

Recently my polo 1.0 has been having issues starting, but there is no method to why it will or won't start, it either cranks over for ages or will start as it should. When it doesn't start the fuel pump relay clicks away madly and it seems to fire once when you come off the starting stage of the ignition. I first plugged it in on the diagnostics and found cam sensor was apparently at fault, but cleared the code and it started like it should. Couple days later it started playing up again I plugged it back in and had CTS along with cam sensor come up, but again cleared them and it was fine, and after a quick test drive they haven't come back.

But now, I have an immobiliser fault for Engine, ABS and airbag, and cleared them and again it was okay. After a 300 mile round trip yesterday, with it starting fine every time it had to, this morning it struggled to start and now has the EPC, Engine check and ABS light on constantly.

Any ideas as it seems as soon as you think you find the solution it just brings more faults up When driving though it runs as it should, but does seem a bit more thirsty than normal.
A lot to read but any ideas/help appreciated! Cheers!

[alexperkins]

If the cam sensor is showing a fault, get it replaced as that is a headache of a sensor

Your geting alot of random errors there - check the engine earth straps are good, and the battery is in good condition

[stephen31]

Meant to say, replaced the cam sensor with a genuine vw one, but when the new one is in the car it will not start, doesn't even attempt to fire sort of thing. Checked the voltage of the battery and that seems good, as for the earth straps I haven't checked that so that will be my next step! Cheers

[alexperkins]

Does the starter even turn? You might have a faulty ignition switch

[stephen31]

Starter turns the engine over as normal, I replaced it about 6 months ago. It's just strange as the car runs just as good as normal, it's just throwing faults up all over the place. I have had code 01314 - Engine ECU not allowed
And
01176 - Key not allowed
I've had a look at my key and there is a deep scratch and dent on the chip of the key.
Any ideas?

[937carrera]

Definitely check the condition of the battery and the output of the alternator. The immobiliser error could simply to be related to low voltage when cranking and you have other underlying problems.

If there's an immo fault the car will generally start and die after a couple of seconmds

[937carrera]

Definitely check the condition of the battery and the output of the alternator. The immobiliser error could simply to be related to low voltage when cranking and you have other underlying problems.

If there's an immo fault the car will generally start and die after a couple of seconds

[stephen31]

Battery is healthy, and regarding the alternator is this a case of checking the battery voltage when the cars running and turning lights on and off?

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[alexperkins]

Key not allowed could well be a fault with the chip

If the immobiliser isn't linking it'll turn the car off even if it's running

[stephen31]

It's hard to see, but would that dent/scrape be causing issue to the immobiliser?

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[alexperkins]

The chip is inside the black key housing - presume you are referring to the dent in the plastic where the metal meets the plastic on the key itself

[937carrera]

As Alex says, the important bit is the little RFID type chip that's within the head of the key itself, you can't see it unless you separate the two halves of the key.

Check the battery voltage with the car running lghts on and off as you say. I bought a car with what looked like an IMMO problem and the issue was the alternator.

One of my cars also will only start with one of the keys, the IMMO throws an error code for weak signal if I try the other and the car dies a couple of seconds after starting. If however I have got the car started, switch off, swap the keys over it will start and run with the second key (main key is out of the car at this point). It's a strange one that I haven't sorted yet.

[stephen31]

Is there anyway to test the chip inside the key? And is this the sole problem or does it sound like there is another underlying problem somewhere due to ABS, EPC and EML light coming on solely when cranking?

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[stephen31]

Thanks for the suggestions guys.
Il check the alternator and earths tomorrow. Talking of that, once the car has started it seems to start as normal again without any issues, it's usually the initial start of the day that's causing an issue, so I might try a key before much else

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[937carrera]

Just so you know you can't just try a key. The little tag is coded to the Immobilisor / ECU. Unless you transfer over the little chip as well the IMMO will operate. I suspect the IMMO fault is a consequence of something else going on.