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If you ever get your C40 stuck in a state where:
  • the key fobs don't work to lock/unlock/start the car;
  • GPS is stuck in one location on the map;
  • You get an error on the driver display that says "SOS / eCall Service required";
  • There's a red "SOS" icon illuminated on the driver display;
. . . and none of the usual reset options help (neither the IHU center display reset nor the modem reset), then this post is for you. Very likely the TCAM (communications module) in your car has found itself in a non-recoverable error state and needs a full power-off-and-restart. This is complicated by the fact that the TCAM has its very own backup battery, so you need to remove the battery AND disconnect a fuse to get it to fully turn off.

There are some other threads and posts about how to reset your TCAM in the XC40 and C40, but when I had to do it myself on my C40, I still had to figure a few things out, and I discovered some shortcuts. Hopefully this will simplify the process for others.

First of all, if this problem occurs, you can STILL DRIVE THE CAR. To start it you need to place your key fob on the short-range NFC sensor, inside the center console directly in front of the trash bin. There's a little key icon imprinted on the surface there to show you where to put it. You'll need to use the metal key inside your fob to lock and unlock your doors, but you shouldn't be stranded as long as your main battery is charged.

If you haven't already, try both types of reset linked above. The center display reset is easy. The modem reset can be challenging, because it requires you to lock the doors - but your fob probably isn't working, so you can't touch the lock surface on the door handle. What I had to do was: (a) change the lock setting in the Settings menu (Settings - Controls - Lock) to "one door," then sit in the driver's seat, press the lock button on the door, then exit the vehicle. Use the actual metal key inside the fob to lock the driver's door using the keyhole hidden under the door handle. In my case, I then had to bump the door closed with my hip because pulling on the door handle to access the keyhole caused the door to pop open a little. You can still lock and shut the door - just make sure you don't lock the key inside!

Then, as noted in the link, leave your car alone for an hour, then go back, unlock the door (using the metal key again), sit inside and see if you can start the car.

If not, then we do the TCAM reset, which requires two things: (1) disconnecting the TCAM backup battery, and (2) disconnecting the TCAM power supply by removing its fuse. Both of those things are pretty easy to do once you figure it out, and the only tool you will need is a small (1/8" or 3/32") slot-type screwdriver.

STEP 1 - TCAM Backup Battery ("BUB")

There are some good photos of the backup battery location here, which show the XC40. The C40 has the same layout. Lay your rear seatbacks down, flip up the cargo area floor, and pull the metal retainer clips out of their holes and slots on each side. This is easy enough to do. Then tip the whole cargo floor out of the way as shown in that first photo.

Right behind the rear seatbacks, on the driver's side of the car, the rectangular TCAM backup battery sits in a horizontal position clipped to a plastic holder. Follow the red arrow in that first photo from the linked post.

The photos at the link above show both the cargo floor retainer clips (circled) and the battery position (arrow) - this is valid for the C40 in addition to the XC40.

Here's a picture of the battery, removed:

Hand Gesture Finger Gadget Font


You can see that there's a pivot hook A on the left side and a retainer clip B on the right that snaps into a slot in the battery holder. You can use your finger to push that retainer clip leftward, under the battery holder (where it is screwed to the car body), to release the battery from the holder. Pivot the right side upward and slide the battery out. It will still be connected to its wiring harness.

To remove the wire connector, hold the battery so the connector faces you and the battery's retainer clip faces down. Here's what that looks like:

Hood Motor vehicle Automotive tire Gas Automotive design


On the connector, to the immediate right of the four wires is a tiny black plastic tab inside a rectangular recess. That tab gets pushed INWARD (toward the left in the photo) toward the wires to release the connector. Use a small slotted screwdriver to push that tab while pulling gently on the wires. Here's what the connector looks like from the opposite side so you can see how that small tab latches the connector in place:

Finger Cable Gadget Wire Auto part


That's it for the battery. It should be totally disconnected at this point.

STEP 2 - TCAM Fuse

* NOTE: This documentation is based on a US car - I don't know if other regions have the same fuse layout. *

According to Volvo documentation, the TCAM is powered by fuse #27 in the fuse box under the passenger side carpet. That particular fuse is located in the row of fuses at the bottom right of the fuse box, specifically the third-last (counting from the right) 5A fuse, which is the fifth-last fuse overall in that row, or the sixth-last fuse position if you count an empty slot at the end. The last six fuse positions are -5A-5A-5A-15A-10A-[blank]. Pull that single 5A fuse using the convenient little yellow fuse-puller tool at the bottom of the box. It will look like below:

Circuit component Passive circuit component Hardware programmer Audio equipment Electronic engineering


After you have pulled the battery and the fuse, go have a beverage of your choice. I waited about 15 minutes. I don't know how long is necessary.

Then reinstall the fuse and the battery - you can just push the fuse back in where it came from using your finger (orientation shouldn't matter), push the wire connector back onto the TCAM backup battery (the tab should click into place lightly), then snap the battery back into its holder (insert the hook A, then pivot the battery down until the retainer B snaps in).

That's it! Now give it a couple minutes to reboot, and go see if your key fobs work. This worked for me. And now that I have done it, I could probably repeat the process in less than five minutes (except for the waiting step obviously!). Notably, I did NOT need to disconnect the 12V battery or the main drive battery, which was a happy discovery.

I hope this helps.
 

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If you ever get your C40 stuck in a state where:
  • the key fobs don't work to lock/unlock/start the car;
  • GPS is stuck in one location on the map;
  • You get an error on the driver display that says "SOS / eCall Service required";
  • There's a red "SOS" icon illuminated on the driver display;
. . . and none of the usual reset options help (neither the IHU center display reset nor the modem reset), then this post is for you. Very likely the TCAM (communications module) in your car has found itself in a non-recoverable error state and needs a full power-off-and-restart. This is complicated by the fact that the TCAM has its very own backup battery, so you need to remove the battery AND disconnect a fuse to get it to fully turn off.

There are some other threads and posts about how to reset your TCAM in the XC40 and C40, but when I had to do it myself on my C40, I still had to figure a few things out, and I discovered some shortcuts. Hopefully this will simplify the process for others.

First of all, if this problem occurs, you can STILL DRIVE THE CAR. To start it you need to place your key fob on the short-range NFC sensor, inside the center console directly in front of the trash bin. There's a little key icon imprinted on the surface there to show you where to put it. You'll need to use the metal key inside your fob to lock and unlock your doors, but you shouldn't be stranded as long as your main battery is charged.

If you haven't already, try both types of reset linked above. The center display reset is easy. The modem reset can be challenging, because it requires you to lock the doors - but your fob probably isn't working, so you can't touch the lock surface on the door handle. What I had to do was: (a) change the lock setting in the Settings menu (Settings - Controls - Lock) to "one door," then sit in the driver's seat, press the lock button on the door, then exit the vehicle. Use the actual metal key inside the fob to lock the driver's door using the keyhole hidden under the door handle. In my case, I then had to bump the door closed with my hip because pulling on the door handle to access the keyhole caused the door to pop open a little. You can still lock and shut the door - just make sure you don't lock the key inside!

Then, as noted in the link, leave your car alone for an hour, then go back, unlock the door (using the metal key again), sit inside and see if you can start the car.

If not, then we do the TCAM reset, which requires two things: (1) disconnecting the TCAM backup battery, and (2) disconnecting the TCAM power supply by removing its fuse. Both of those things are pretty easy to do once you figure it out, and the only tool you will need is a small (1/8" or 3/32") slot-type screwdriver.

STEP 1 - TCAM Backup Battery ("BUB")

There are some good photos of the backup battery location here, which show the XC40. The C40 has the same layout. Lay your rear seatbacks down, flip up the cargo area floor, and pull the metal retainer clips out of their holes and slots on each side. This is easy enough to do. Then tip the whole cargo floor out of the way as shown in that first photo.

Right behind the rear seatbacks, on the driver's side of the car, the rectangular TCAM backup battery sits in a horizontal position clipped to a plastic holder. Follow the red arrow in that first photo from the linked post.

The photos at the link above show both the cargo floor retainer clips (circled) and the battery position (arrow) - this is valid for the C40 in addition to the XC40.

Here's a picture of the battery, removed:

View attachment 4813

You can see that there's a pivot hook A on the left side and a retainer clip B on the right that snaps into a slot in the battery holder. You can use your finger to push that retainer clip leftward, under the battery holder (where it is screwed to the car body), to release the battery from the holder. Pivot the right side upward and slide the battery out. It will still be connected to its wiring harness.

To remove the wire connector, hold the battery so the connector faces you and the battery's retainer clip faces down. Here's what that looks like:

View attachment 4815

On the connector, to the immediate right of the four wires is a tiny black plastic tab inside a rectangular recess. That tab gets pushed INWARD (toward the left in the photo) toward the wires to release the connector. Use a small slotted screwdriver to push that tab while pulling gently on the wires. Here's what the connector looks like from the opposite side so you can see how that small tab latches the connector in place:

View attachment 4816

That's it for the battery. It should be totally disconnected at this point.

STEP 2 - TCAM Fuse

* NOTE: This documentation is based on a US car - I don't know if other regions have the same fuse layout. *

According to Volvo documentation, the TCAM is powered by fuse #27 in the fuse box under the passenger side carpet. That particular fuse is located in the row of fuses at the bottom right of the fuse box, specifically the third-last (counting from the right) 5A fuse, which is the fifth-last fuse overall in that row, or the sixth-last fuse position if you count an empty slot at the end. The last six fuse positions are -5A-5A-5A-15A-10A-[blank]. Pull that single 5A fuse using the convenient little yellow fuse-puller tool at the bottom of the box. It will look like below:

View attachment 4817

After you have pulled the battery and the fuse, go have a beverage of your choice. I waited about 15 minutes. I don't know how long is necessary.

Then reinstall the fuse and the battery - you can just push the fuse back in where it came from using your finger (orientation shouldn't matter), push the wire connector back onto the TCAM backup battery (the tab should click into place lightly), then snap the battery back into its holder (insert the hook A, then pivot the battery down until the retainer B snaps in).

That's it! Now give it a couple minutes to reboot, and go see if your key fobs work. This worked for me. And now that I have done it, I could probably repeat the process in less than five minutes (except for the waiting step obviously!). Notably, I did NOT need to disconnect the 12V battery or the main drive battery, which was a happy discovery.

I hope this helps.
Great post.
One question: does it effect the warrantee at all? Has anyone asked their dealership ?

Sounds like this is a tool we need (wish it was just a switch )

Nice guide.

Cheers
 

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I don't see how it could affect the warranty. There is no way for them to know if you have done this.
Other than an internal log which might have complete power off registered.

But I am sure you are right at the car seems to lack enough data logging :)
 

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If you ever get your C40 stuck in a state where:
  • the key fobs don't work to lock/unlock/start the car;
  • GPS is stuck in one location on the map;
  • You get an error on the driver display that says "SOS / eCall Service required";
  • There's a red "SOS" icon illuminated on the driver display;
. . . and none of the usual reset options help (neither the IHU center display reset nor the modem reset), then this post is for you. Very likely the TCAM (communications module) in your car has found itself in a non-recoverable error state and needs a full power-off-and-restart. This is complicated by the fact that the TCAM has its very own backup battery, so you need to remove the battery AND disconnect a fuse to get it to fully turn off.

There are some other threads and posts about how to reset your TCAM in the XC40 and C40, but when I had to do it myself on my C40, I still had to figure a few things out, and I discovered some shortcuts. Hopefully this will simplify the process for others.

First of all, if this problem occurs, you can STILL DRIVE THE CAR. To start it you need to place your key fob on the short-range NFC sensor, inside the center console directly in front of the trash bin. There's a little key icon imprinted on the surface there to show you where to put it. You'll need to use the metal key inside your fob to lock and unlock your doors, but you shouldn't be stranded as long as your main battery is charged.

If you haven't already, try both types of reset linked above. The center display reset is easy. The modem reset can be challenging, because it requires you to lock the doors - but your fob probably isn't working, so you can't touch the lock surface on the door handle. What I had to do was: (a) change the lock setting in the Settings menu (Settings - Controls - Lock) to "one door," then sit in the driver's seat, press the lock button on the door, then exit the vehicle. Use the actual metal key inside the fob to lock the driver's door using the keyhole hidden under the door handle. In my case, I then had to bump the door closed with my hip because pulling on the door handle to access the keyhole caused the door to pop open a little. You can still lock and shut the door - just make sure you don't lock the key inside!

Then, as noted in the link, leave your car alone for an hour, then go back, unlock the door (using the metal key again), sit inside and see if you can start the car.

If not, then we do the TCAM reset, which requires two things: (1) disconnecting the TCAM backup battery, and (2) disconnecting the TCAM power supply by removing its fuse. Both of those things are pretty easy to do once you figure it out, and the only tool you will need is a small (1/8" or 3/32") slot-type screwdriver.

STEP 1 - TCAM Backup Battery ("BUB")

There are some good photos of the backup battery location here, which show the XC40. The C40 has the same layout. Lay your rear seatbacks down, flip up the cargo area floor, and pull the metal retainer clips out of their holes and slots on each side. This is easy enough to do. Then tip the whole cargo floor out of the way as shown in that first photo.

Right behind the rear seatbacks, on the driver's side of the car, the rectangular TCAM backup battery sits in a horizontal position clipped to a plastic holder. Follow the red arrow in that first photo from the linked post.

The photos at the link above show both the cargo floor retainer clips (circled) and the battery position (arrow) - this is valid for the C40 in addition to the XC40.

Here's a picture of the battery, removed:

View attachment 4813

You can see that there's a pivot hook A on the left side and a retainer clip B on the right that snaps into a slot in the battery holder. You can use your finger to push that retainer clip leftward, under the battery holder (where it is screwed to the car body), to release the battery from the holder. Pivot the right side upward and slide the battery out. It will still be connected to its wiring harness.

To remove the wire connector, hold the battery so the connector faces you and the battery's retainer clip faces down. Here's what that looks like:

View attachment 4815

On the connector, to the immediate right of the four wires is a tiny black plastic tab inside a rectangular recess. That tab gets pushed INWARD (toward the left in the photo) toward the wires to release the connector. Use a small slotted screwdriver to push that tab while pulling gently on the wires. Here's what the connector looks like from the opposite side so you can see how that small tab latches the connector in place:

View attachment 4816

That's it for the battery. It should be totally disconnected at this point.

STEP 2 - TCAM Fuse

* NOTE: This documentation is based on a US car - I don't know if other regions have the same fuse layout. *

According to Volvo documentation, the TCAM is powered by fuse #27 in the fuse box under the passenger side carpet. That particular fuse is located in the row of fuses at the bottom right of the fuse box, specifically the third-last (counting from the right) 5A fuse, which is the fifth-last fuse overall in that row, or the sixth-last fuse position if you count an empty slot at the end. The last six fuse positions are -5A-5A-5A-15A-10A-[blank]. Pull that single 5A fuse using the convenient little yellow fuse-puller tool at the bottom of the box. It will look like below:

View attachment 4817

After you have pulled the battery and the fuse, go have a beverage of your choice. I waited about 15 minutes. I don't know how long is necessary.

Then reinstall the fuse and the battery - you can just push the fuse back in where it came from using your finger (orientation shouldn't matter), push the wire connector back onto the TCAM backup battery (the tab should click into place lightly), then snap the battery back into its holder (insert the hook A, then pivot the battery down until the retainer B snaps in).

That's it! Now give it a couple minutes to reboot, and go see if your key fobs work. This worked for me. And now that I have done it, I could probably repeat the process in less than five minutes (except for the waiting step obviously!). Notably, I did NOT need to disconnect the 12V battery or the main drive battery, which was a happy discovery.

I hope this helps.
I experienced a GPS issue where it was stuck on one location, A reset of the TCAM unit by pressing and holding the front defroster button resolved the issue.
 

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Thanks so much for posting this solution. Worked like a charm. And thanks for the step by step with pictures. The only step I had trouble with was locating and removing the cover for the fuse box. Figured it out, but it wasn't as clear as all the other steps.
 
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