My 2004 XC70 runs fine for a few months then decides to go in limp mode at times or perhaps not start for hours or days. When this occurs, I have had Brake Failure messages, along with the brake light and abs light showing, Brake failure drive safely message, Transmission service reqd message, engine system service reqd message, reduced engine performance message. Sometimes the tach, speedo, and temp guage quit working. When it is doing this, I sometimes hear a rather rapid, loud repeated ticking sound like a relay under the dash when the key is turned on. A few times Ive experienced a rather loud thud towards the rear of the car when the transmission goes into limp mode. The check engine light is also on. Let it sit for a few hours or a day and everything is back to normal working fine. The local volvo service dept has looked at it 4 times with no solution because they say no codes will stick and they cant determine the problem until whatever computer module is acting up fails completely. They want me to leave the car with them but the last two episodes had an interval of 7 months. Any help, suggestions etc would be appreciated.

 

Honestly, sounds like a power/ground issue. Have you checked the basics like the battery and connections? Also check power connections up front. If the power and grounds all seem to be in working order I would be looking at the ignition switch.

 

Hello
I have been doing search for over a year now, I bought a used XC70 in great condition and the day I picked it up , less than 30 miles away from the seller's house the car acted in very strange way something I never experience in my 30 years of playing with cars, All the gages died , while the car still driven, no electrical connection of any kind. no horn, no wipers, AC was on full blast and could not turn it off or down, Limp mode and total confusion on my side,
To make the long story short , The CEM module simply was over heating (was about 95 degrees that day) I managed to arrive home safe and next day the car was running perfect, took it for short trip (100 miles) and came back safe,, wow, , I parked the car for several weeks , got back to it and here was the floor flooded with water, I cleaned the floor and started the car, turn the heater full blast and guess what?? it happened not more than 15 minutes later, now I am convinced that something is overheating but did not know what exactly, after I did my home work and searched every possible way I found the CEM is the cause, ,, Found great company in Canada that will rebuild or replace the CEM for around $500.00 VS what the local STEALER ($1450),
When I got the CEM back I installed small computer fan on top of the module for extra cooling,
Now I am very happy with the new CEM and the car is running amazingly good, I took the CEM out myself and reinstalled it , total invested time was less than an hour,
Hope this will help someone who is very frustrated with unexplainable VOLVO behaving.

 

We are having a similar issue - but it floods when it rains I think. Was it raining when your flooded?