ECU packed up on my 850 T5

[Djstaffy]

Looks like my ECU has packed up on my N plate
850T5 estate....mechanic plugged into it today & said it's not sending signals out to most of sensors...it's done 250,000 miles.....is there a simple fix..can I get a new ECU.... been a great motor...still pulls well...or is it gonna cost too much
Any suggestions welcome
Thanks
Danny

[Luxobarge]

Hmm, what did he "plug" into it? Does he know it's not OBDII compliant, and therefore a normal OBDII scanner won't work? Or was he using the correct Volvo diagnostics? If it has the diagnostic plug in the centre console, don't be fooled by the fact that it may say "OBD" on it.....

Extremely rare for ECUs to go faulty on these cars.

[buick boy]

Had the same problem on my old 850 t5 . The ecu is located on the side of the engine bay in an air cooled box . I found that I had water ingress which affected the connections on the multi-plug that it slots into . A bit of cleaning of the terminals and pushing in and out a few times and away she went . Worth a try before you start spending money .

[Djstaffy]

thanks for the replies.. all i know from the mechanic is that he couldnt get full access to the ecu but it was showing that not sending signals to main engine sensors? i'll pull the ecu out and clean & dry it too you never know!!
thanks

[Luxobarge]

By all means pull it, dry it and re-seat it, but I've a very strong suspicion that the ECU isn't the problem - your mechanic's description doesn't make sense either, it's the sensors that send a signal to the ECU, not the ECU sending signals to the sensors for a start. What did he observe on his scanner that led him to that conclusion? I doubt if he learned anything of value if he couldn't connect to the ECU, so I can't see how he came to the conclusion he did.

Can you confirm the year of your car? Others on here that know more about the 850s than me will be able to tell you how to read the codes on your model, but it almost certainly won't be by using a normal OBDII scanner.

Also, assuming that I'm right and there's nothing wrong with the ECU, can you tell us what symptoms you have with the car? Does it run at all? Does it run badly, and if so in what way? Is the Engine Management Light on when running? We may be able to help you with the real cause of the problem if you can give us a lot more information, although you still might have to find a way of reading the codes.

Cheers!

[Djstaffy]

Originally Posted by Luxobarge

By all means pull it, dry it and re-seat it, but I've a very strong suspicion that the ECU isn't the problem - your mechanic's description doesn't make sense either, it's the sensors that send a signal to the ECU, not the ECU sending signals to the sensors for a start. What did he observe on his scanner that led him to that conclusion? I doubt if he learned anything of value if he couldn't connect to the ECU, so I can't see how he came to the conclusion he did.

Can you confirm the year of your car? Others on here that know more about the 850s than me will be able to tell you how to read the codes on your model, but it almost certainly won't be by using a normal OBDII scanner.

Also, assuming that I'm right and there's nothing wrong with the ECU, can you tell us what symptoms you have with the car? Does it run at all? Does it run badly, and if so in what way? Is the Engine Management Light on when running? We may be able to help you with the real cause of the problem if you can give us a lot more information, although you still might have to find a way of reading the codes.

Cheers!

hi thanks for the reply
its a 96 N plate T5
regarding what the mechanic told me i dont understand really all this modern terminology (my daily car is an amazon which i can understand..) ...something about voltage dropping out to various sensors .. theres no engine management light coming on dash...but the arrow icon appears flashing (its an auto)
the car will occasionally start (after about 20 attempts) then wont start again if you switch it off...it may then start but wont rev up, then wont start again & more attempts may start but runs rough....& so on
thanks
Danny

[s1monc]

A second hand 4.3 ECU for an auto won’t be much secondhand, lots of people have upgraded to 4.4 so should be easy to source a 4.3 for an auto.

[Clan]

Originally Posted by Djstaffy

Looks like my ECU has packed up on my N plate
850T5 estate....mechanic plugged into it today & said it's not sending signals out to most of sensors...it's done 250,000 miles.....is there a simple fix..can I get a new ECU.... been a great motor...still pulls well...or is it gonna cost too much
Any suggestions welcome
Thanks
Danny

nothing will come out if it has no power ,also are there any inputs working ?
find someone who knows what they are doing ... condemning an ECU is the VERY last thing after PROVING it is faulty.

[cyclogenesis]

You might also want to check your earth strap. I had a similar issues some years ago with starting problems and then the main stealer stated the ECUs were dead. After some deduction from my layman self, I asked them to check the battery circuit and there was a rotten earth strap that was causing intermittent starting and then failed completely. No power, no ECU data!