Volvo CEM immobilizer PIN

[Tamas1337]

Hi everyone,

I have recently taken up the adventure of cracking my Volvo V70 P2 from 2007 wide open, partly to take full control over my car, and mainly to change the default audio system, with plans to install another radio capable of Android Auto + integrating it into the car, so I can use my steering wheel controls. I am also thinking about getting a tune from VDASH, for a bit more power and for disabling the EGR valve so the engine runs smoother, and I would also like to future-proof myself by giving me the possibility to repair all parts of my car, e.g. changing keys if one were to get lost or destroyed.

After getting the usual things like the Super J2534 (or Mongoose Pro JLR) and VIDA and VDASH installed, only then I realized I need the PIN to my CEM. So I built this (https://github.com/vtl/volvo-cem-cracker) Volvo CEM PIN Cracker and it actually worked!

However, after opening VDASH connected to my car I realized, there is even MORE PINS??? After clicking on the Security tab I tried decoding this "CEM IMMO" PIN, however it doesn't even start. I saw some audio settings being greyed out so (something about MOST, which I shouldn't have, the HU-650 being installed from the factory) I thought that I have to get this PIN to achieve what I want to do.

So, 3 questions:

1. Do I even need to get this PIN for changing the radio (to a 3rd party one)?

2. What exactly does this CEM IMMO PIN enable me to do?

3. Is there any way I can use OBDII to do this or do I have to disassemble my car to get to my CEM directly?

If it helps, my CEM has the Partnumber 30786889 and the engine is the B5244S, I live in Europe and the car is also european.
I didn't know if this is the right sub-forum for this so apologies if I'm wrong here!

[jonesg]

people install aft mkt double din radios all the time, theres an adapter you can add that enables steering wheel controls.

[vtl]

1. No

2. ECM (engine computer) and CEM need to know immobilizer pin (stay in sync) or the engine start won't be permitted

3. With CEM pin known you can read and write CEM using third party software

[Tamas1337]

1. No

2. ECM (engine computer) and CEM need to know immobilizer pin (stay in sync) or the engine start won't be permitted

3. With CEM pin known you can read and write CEM using third party software

Hi, thanks for your reply,
so I understood correctly, that adding an aftermarket radio is very much possible with only my CEM PIN, which I already got.
This synchronization between the CEM and ECM, what does it affect?

One thing I also want do disable is the automatic headlight, as right now the light knob being on position 0 still turns on my low beam when the car is running. If I turn this automatic headlight off, will the car still start?

If I were to load another engine tune onto the ECM (with VDASH) would that mess with the CEM-ECM synchronization and would my car not start anymore?

Does changing the language affect the ability to start the car?

Also, even if I don't need this CEM Immobilizer PIN for the changes I would want to make, how would I go about getting this CEM IMMO PIN? Is there some tutorial or any instructions on how to get it from my P2?

Also, is that you vtl, who made this github project? Amazing work, wish I had the knowledge and ability to code, helping this community instead of needing help right now. Maybe one day. Did you ever need to get this specific PIN for anything you did and what have you modified in your car?

[Tamas1337]

people install aft mkt double din radios all the time, theres an adapter you can add that enables steering wheel controls.

Hi, thanks for your help as well,
that is what I wanted to do, get an adapter so I can have steering wheel control, reverse light, ignition, speedpulse; basically this adapter: https://www.caraudio24.de/Zubehoer/CAN- ... 29447.html

However, I thought that I had to tell the car to forget the original headunit and use an aftermarket one, somewhere in the CEM settings? But that is why I'm a bit scared, because I don't know if changing anything will desynchronize the CEM and ECM and the car won't let me start it anymore.

[vtl]

Hi, thanks for your reply,
so I understood correctly, that adding an aftermarket radio is very much possible with only my CEM PIN, which I already got.

You don't need any pin to replace the radio in this car.

This synchronization between the CEM and ECM, what does it affect?

This is a part of immobilizer system, to prevent theft. 20 years later, of course, it only prevents owners from fixing their broken car

One thing I also want do disable is the automatic headlight, as right now the light knob being on position 0 still turns on my low beam when the car is running. If I turn this automatic headlight off, will the car still start?

The car will start. This is a CEM configuration change, you need CEM pin for that. Need VDASH or alike system to do the change.

If I were to load another engine tune onto the ECM (with VDASH) would that mess with the CEM-ECM synchronization and would my car not start anymore?

Yes and no. The ECM software is stored in flash chip, while configuration, synchronization bits and software checksum are in EEPROM chip. Even if you replace the flash chip directly, the car will still start, as the immo code is stored in EEPROM. You will have a software checksum mismatch code registered, but it does not light MIL up. I drive my car like that for many years Most tuning software update the checksum properly, though, so you have no codes.

Does changing the language affect the ability to start the car?

No.

Also, even if I don't need this CEM Immobilizer PIN for the changes I would want to make, how would I go about getting this CEM IMMO PIN? Is there some tutorial or any instructions on how to get it from my P2?

VDASH and some other software can synchronize CEM and ECM for you. You need just the CEM pin for that, which you already have.

Also, is that you vtl, who made this github project? Amazing work, wish I had the knowledge and ability to code, helping this community instead of needing help right now. Maybe one day. Did you ever need to get this specific PIN for anything you did and what have you modified in your car?

Yes, it's me. The cracker is a collaboration work among many people, but the foundation was done by T5Luke and me.

I was very bored at my work back then and decided to entertain myself with some brain activity. Haven't actually used CEM pin for any change.

[vtl]

Hi, thanks for your help as well,
that is what I wanted to do, get an adapter so I can have steering wheel control, reverse light, ignition, speedpulse; basically this adapter: https://www.caraudio24.de/Zubehoer/CAN- ... 29447.html

However, I thought that I had to tell the car to forget the original headunit and use an aftermarket one, somewhere in the CEM settings? But that is why I'm a bit scared, because I don't know if changing anything will desynchronize the CEM and ECM and the car won't let me start it anymore.

You just replace the head unit. There will be a code stored for missing AUM, but MIL is not up for that one.

[Tamas1337]

VDASH and some other software can synchronize CEM and ECM for you. You need just the CEM pin for that, which you already have.

Alright, thank you a lot, you already helped me understand these things a bit better.
However, I worry just a bit, because in VDASH, two days ago, I already tried decoding these IMMO codes:

After doing that, it decoded the UEM IMMO, whatever that is, it didn't decode the CEM IMMO though.
After clicking on the i next to that message, it brought me to this page:

Bildschirmfoto_20251114_174258.png (238.56 KiB) Viewed 264 times

My engine should be supported though, as it is the B5244S:

Bildschirmfoto_20251114_174517.png (191.17 KiB) Viewed 264 times

Am I missing something or is this how it is supposed to be?

Sorry if this doesn't belong to the original question, but then please direct me where I could ask this or who could answer me.

[darylrobert]

im still trying to read CAn bus messages. Android head unit shows this display in "protocol print" but no one knows what it is..

lin bus code?

lin bus code.jpg (44.13 KiB) Viewed 240 times

[vtl]

Steering wheel buttons come from SWM, gearbox selector position comes from TCM. Both are on CAN-bus, not LIN. You need CAN ID and CAN message bytes.

Show the full screen, with everything it prints?