Corrupt CEM Non Start Investigation and Repair Tutorial

[scaro]

Answer my own questions.
Keys was OK.
Changed sync in Cem and ECM to 1:s until sync was ok on bench

Tested in car started right up.

[Dudde]

I have problem with my sync, the ECM will change pin to FF FF FF and security code to 15 55 55 55 55 55.

Change back to correct data, even tried bench flashing correct data to eeprom, everything is good if i look in dha but if i cycle ignition the values go back to the wrong ones.

Anyone have an idea what to do? Tried to change CEM data to match the ECM also but no start.

My fiance is starting to get a little pissed at me for spending all day in garage, but i need the car started so i can continue swapping the engine in my 940.

All help is appreciated

[Mbvolvo2009]

We have issues with none starting v70 d5 automatic diesel 2006 fuses good but we sent our cem to get checked it had water damage so they put data onto another Sent back still no start replaced ecu with the exact same bosch number as ours no codes coming up. But put key into ignition lights on dashboard but no clicking of it turning over dead quite at a loss any help appreciated.
Not sure if we have to get everything reprogrammed

[AliR]

Excellent writeup. My 2004 Volvo V70 2.5T has the same problem. Both keys not responding and the message "Start Prevented Try Again." I don't have any of the tools you used. What I understood from this writeup is that programming new keys would solve this problem. Did i get that right?

Thank you!

Ali R.

[mikeak2001]

Excellent writeup. My 2004 Volvo V70 2.5T has the same problem. Both keys not responding and the message "Start Prevented Try Again." I don't have any of the tools you used. What I understood from this writeup is that programming new keys would solve this problem. Did i get that right?

Thank you!

Ali R.

Unfortunately just programming keys may not solve it, The flash data on this one was corrupt due to a flat battery, This corrupted the 3 byte pin code that is used to programme the keys, that's why the dealer couldn't sort it, pin code that was stored on Volvo servers was being rejected. The data can be manually modified though and reflashed. then key programming can be performed.

[scot850]

When we had the Start prevented message on our o6 XC70, initially I thought it was the antenna that was either dirty or bad, and was pointed to that by another owner. Replacing it made no difference. The issue was we were also only getting it with as it turned out with one key-fob. The one that was seldom used turned out to work fine.

It turned out the transponder ship had failed in the key fob. I found some on Alibaba (AliExpress) and installed the ship into the original fob.
Main issue was the transponder had to be reprogrammed by Volvo, and the only way they could do that is by having the bar code off the original key packaging. I ended up having to buy a new fob to get the info and having it programmed as well. The most important part was all keys had to be reprogrammed, not just the new one or the one with the new transponder. This was to ensure all keys were sync'd to the car.

Neil.

[brbrob]

Thanks and Props to OP MikeAk2001

Having a similar problem on XC90 P2.


https://drive.google.com/file/d/17-N_vK ... sp=sharing

What I have tried so far.
1.) Cleaned CEM Boards, Replaced Surface Mount Components, Capacitors Etc.. general board maintenance while I had it apart.
2.) Measured CANBUS Voltage at OBDII, Pin 6 to Pin 14, Result 61.5 Ohms (Good)
3.) Sent CEM to a cloning service. (Cloning of corrupted value results in two non-working CEM's)
4.) Cutting a New Key and Programming with VIDA. (Result is same issue)

This is obviously my next step as the vehicle is essentially a giant brick in my driveway.

On Order:
Teensy https://www.sparkfun.com/teensy-4-1-headers.html
IO Terminal https://autotechelec.com/shop/tools/io-terminal-2/

[Dudde]

Thanks and Props to OP MikeAk2001

Having a similar problem on XC90 P2.


https://drive.google.com/file/d/17-N_vK ... sp=sharing

What I have tried so far.
1.) Cleaned CEM Boards, Replaced Surface Mount Components, Capacitors Etc.. general board maintenance while I had it apart.
2.) Measured CANBUS Voltage at OBDII, Pin 6 to Pin 14, Result 61.5 Ohms (Good)
3.) Sent CEM to a cloning service. (Cloning a corrupted value results in two non-working CEM's)
4.) Cutting a New Key and Programming with VIDA. (Result is same issue)

This is obviously my next step as the vehicle is essentially a giant brick in my driveway.

Have Ordered Teensy https://www.sparkfun.com/teensy-4-1-headers.html

Now to procure IO Terminal.

If you have the files send them to me, I'll help

[brbrob]

If you have the files send them to me, I'll help

Thanks in advance. Once the hardware arrives I will post updates and most likely request help.

[Dudde]

If you have the files send them to me, I'll help

Thanks in advance. Once the hardware arrives I will post updates and most likely request help.

Do you have any tools? Dice?

If you have dice you don't need teensy or io terminal