2004 S60 Troubleshoot heat soak ECM, BCM, CEM, & TCM Topic is solved

hankb · Post by **hankb** » 11 May 2015, 19:59

I held out on sharing this because I didn't want to jump the gun... and even though I'm optimistic, I'm not certain - but I think I am closer to a resolution for my problem. I had planned to send my ECU to XeMODeX, so I ordered the ECU removal tool from ipd. When I got it on May 6, I pulled out the ECU and inspected it, then re-installed it. That was 5 days ago, and the car has driven perfectly since that moment. At this moment it looks like there was a loose connection at the ECU mount that seems to be closed now. I'm very optimistic.. but I'll be back!

Post by **oragex** » 12 May 2015, 08:26

That's interesting. Is the small ecu fan still hissing when the engine shuts off? This will check the fan works fine. There is also a plastic pipe where the fan sits, that can get disconnected from the ECU box. This pipe helps evacuate the hot air from the ECU.

Please come back with a follow up after some time. I have read about at least two other owners with this hard to diagnose issue, and it will be helpful to know if the ECU was indeed the fix.

hankb · Post by **hankb** » 18 May 2015, 16:13

I went trouble-free for 12 days in weather that I would have expected trouble. Today the car went haywire in 50% humidity and 80° F. @Oragex I can't tell that the hot air evac fan is working - I can't access it while the car is running because it's blocked by the ECU and TCM - I might need to remove the coolant reservoir/powersteering reservoir to pull it out during operation to see what it's doing. Can I ask about the operation of that fan? At first I thought it pulled cool air in from the cabin to the box, but based on your comment I'm guessing it sucks air out of the box and exhausts it into the cowl - which is correct?

Post by **abscate** » 18 May 2015, 20:16

I'll try peek at mine in the morning

Post by **jimmy57** » 19 May 2015, 06:24

The duct runs to the firewall and is connected to the evaporator housing. The climate system fan will push some air into the control module box. If the box gets hot (sort of assumed to be due to climate fan not being on) then the control module fan will be run by the ECM based on the board mounted temp sensor. The fan running is pretty rare. The air is pulled from climate box through duct to the control module box.

Post by **abscate** » 19 May 2015, 09:40

hankb wrote:I went trouble-free for 12 days in weather that I would have expected trouble. Today the car went haywire in 50% humidity and 80° F. @Oragex I can't tell that the hot air evac fan is working - I can't access it while the car is running because it's blocked by the ECU and TCM - I might need to remove the coolant reservoir/powersteering reservoir to pull it out during operation to see what it's doing. Can I ask about the operation of that fan? At first I thought it pulled cool air in from the cabin to the box, but based on your comment I'm guessing it sucks air out of the box and exhausts it into the cowl - which is correct?

Hank - did you try lifting and reseating the ECU again to see if it cured it?

hankb · Post by **hankb** » 19 May 2015, 09:52

That's the first thing I tried when I got the tool - I blew some air into the box to clear out dust and used DeOxit on the ECU and TCM connections and reseated them carefully. After I did that it performed very well for 12 days (which is remarkable given the previous situation). I currently believe it's some kind of overheating/airflow issue in the box; I'm not sure if it's a heat sink issue with the ECU (I did see three mosfets inside the ECU that seem to use the aluminium case as a heat sink), or if it's an airflow issue in the box itself. My wife discovered last year that we could prevent or limit the failures by running the AC on our feet with max airflow, I initially thought it was cooling the CEM (in the cabin), now I believe the cold air from the cabin is keeping the ECU from overheating. I am actually pretty excited to feel this close to resolving a 6-year problem! I don't detect any air coming into the duct in the box, can someone suggest a way to improve/increase airflow coming in? I got a used box fan ("box fan" - I'm referring to the volvo factory fan for the ECU/TCM box) on ebay for $15 so I'm going to tinker with it a bit to learn more about how the system works. By the way- Thank you all for providing so much support. I'm sincerely appreciative.

Post by **oragex** » 19 May 2015, 10:37

hankb wrote:@Oragex I can't tell that the hot air evac fan is working - I can't access it while the car is running because it's blocked by the ECU and TCM -

There is not need to remove anything, not even to pop the hood open. After a drive in a hot day, this fan will keep running for a few minutes after shutting the engine off. I can hear it hissing from inside the car for a few minutes. The fan is located at the back of the ECU box - towards the cabin, inside the larger plastic duct, just at the ECU box rear wall. This duct also sometimes gets crushed by the p/s reservoir and can get disconnected from the ECU box. I sealed mine around with some tape. The small fan will remove the air inside the ECU and will blow it towards the cabin. It is crucial this small fan works, funny thing it's a small cheap china kind of motor that can be found in some toys - well, perhaps it's a little more robust, but still a critical part meant to cool down the car's main ECU.

Have you tried (with the battery disconnected) unplug the ECU wires and check for any corrosion/broke/dry wiring) ?

Small note, if you need to remove the Coolant reservoir for some reason, always disconnect the electrical level sensor plug nearby, this sensor has a sensitive easy to break wire on it. Saving you a $50 repair:)

Post by **abscate** » 20 May 2015, 08:25

The small fan will remove the air inside the ECU and will blow it towards the cabin.

I think Jimmy has this the other way, and I think he is right - the fan will pull cold air from the cabin towards the ECU

Small note, if you need to remove the Coolant reservoir for some reason, always disconnect the electrical level sensor plug nearby, this sensor has a sensitive easy to break wire on it. Saving you a $50 repair:)

You can feel the sensor break ...just...as the connector becomes visible

hankb · Post by **hankb** » 07 Jun 2015, 08:47

I can hardly believe I'm writing this, but I'm ready to consider my intermittent electrical issue with my 2004 S60 solved. If you've read through the thread, you'll see that I replaced the TCM, CEM, and BCM but continued to experience High Speed CAN crashes in high heat and humidity (above 50% humidity and 80° F). I applied the fix 14 days ago, but I held out on reporting until I could take the car on a long trip. We drove 600 miles this weekend to the Great Smoky Mountains and back in high heat and humidity - and with no car trouble.

The solution? I applied DeoxIT contact cleaner to the ECU connection. The inspiration for DeoxIT came from this youtube link. Note that the product I purchased was not the exact product recommended by the video, but it does appear to have worked (The video recommends the 100% solution, I purchased the 5% solution out of naivety).

Thanks to everyone who has offered help and suggestions here! After dealing with this problem for so long I would recommend that people with a similar problem purchase DeoxIT early in the process and clean out the HS CAN module connectors, then purchase the VIDA tool to narrow down the problem if the DeoxIT doesn't work. I suggest that it is worth the money to buy the $30 ECU/TCM removal tool at the same time you purchase the DeoxIT.

I'm a little hesitant to say this is a complete fix, but I've had this issue for six years and I have never successfully driven it in the heat+humidity condition without experiencing trouble.

2004 S60 Troubleshoot heat soak ECM, BCM, CEM, & TCM Topic is solved

Re: 2004 S60 Electrical problem between ECM, BCM, CEM, & TCM