Recently I purchased a 2006 XC70 that has a no start condition (Start Prevented warning on DIM, no crank) from a family friend. I purchased a brand new battery first as it had been sitting for a while and had a battery low voltage warning on the DIM when purchased. Went ahead and did an oil change to make sure it was topped off and got a fresh set of spark plugs as I had an extra set laying around. With that I confirmed that the motor was turning freely by jumping pins 30 and 87 on the starter relay and from there got to work on inspecting the wiring and general health of the components in the engine bay. Once I had ViDA setup on a laptop and a VXDIAG unit to read the vehicle with, I started digging into the codes and live data. Initially, I had quite a few codes, however after some cleaning and general maintenance and fuse replacement I have narrowed this down to the following four codes repeatedly showing up within ViDA.
CEM-0004 Passenger compartment temperature sensor - Signal too high/Signal missing
CEM-9C03 Antenna/light ring - Signal missing
REM-4F45 Parking assistance sensor 4 - Faulty Signal
REM-1D01 Control module - Internal Fault
With these fault codes remaining, I started by going to the junkyard to acquire a new antenna ring (ensured it passed a resistance check). I installed this and unfortunately it did not change the codes present whatsoever. I then ran a resistance check on my original antenna ring and found that it was passing the check as well. With that I went into the live data to get a better understanding of what was going on. I went to the CEM, and found the following beneath the Immobilizer section:
CEM-Key Type Main Key
CEM-Key number 1
CEM-Number of keys 0
CEM-ID code received Yes
CEM-ID code stored Faulty
CEM-Immobilizer, engine co... Wrong Status
CEM-Immobilizer, start per... Start not approved
I am new to the P2 platform with this vehicle but from what I have been able to find so far it would appear to me that the CEM could be faulty here and not the units surrounding it. What appears to be the most likely cause of this current issue would be that the CEM dumped my EEPROM data and the Immobilizer ID needs to be reset. I have reached this conclusion based on the live data associated with the immobilizer, primarily the first 5 data points. The fact that the key is being recognized as "Main Key" and Key #1 indicates to me that the antenna ring is fully operational, and that the failure point is located in the CEM stored ID code that is checked with that of the Key Fob. This is especially clear with the fact that CEM number of keys is reading as 0 and that CEM id code stored is reading as faulty.
Given all of this, it would seem that a reset/reload of the Immobilizer ID is necessary. But given my inexperience with this platform, I wanted to see if any other potential fixes could be possible here before I move forward with purchasing access to ViDA 2015 as well as a genuine DiCE unit/mongoose cable to perform this fix as it comes with a significant price tag. I have tried all of the key fob tricks like, lock/unlock 5 times, as well as activating panic button and locking/unlocking. Currently trying to remove the wiper arms to gain access to the Top-End of the CEM to check for corrosion although i suspect that this is not a likely issue from the general condition of the components in the car. If any of you have any ideas regarding this issue I am facing I would greatly appreciate your input.
Thank you for your time and reading this post.
