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2009 D5 XC90 Loss of Power, Anti Skid and ABS Pulsing

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Old Oct 26th, 2024, 21:06   #1
Mark101
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Default 2009 D5 XC90 Loss of Power, Anti Skid and ABS Pulsing

I'm hoping for some help in tracking down a power loss / limp mode issue that also seems connected to the ABS system.

A couple of days ago, the "Anti-Skid Service Required" message appeared again. Since buying the car in March, I've seen this message pop up a few times. It’s never affected the car’s performance, so it’s been on the “get to it when I can” list, almost like an old friend checking in.

The other night, just as I was arriving home, the anti-skid message appeared again. I parked the car as usual and thought nothing of it. However, the next day, as soon as I reached the speed where second gear would typically engage, the power suddenly cut. The car still moved, but I could feel the ABS pump engaging and pulsing through the pedal.

I scanned for codes and found a mechanical error related to the front-right sensor. I removed the sensor and noticed signs of wear on the end, likely caused by a rusted and expanding ABS ring. Under the car, I found a large chunk missing from the ring, which made sense as to why the car couldn’t accurately detect the wheel’s rotation, potentially leading to the power loss and ABS fit.

Today, I replaced the ABS ring and sensor (using mid-range parts from Auto Doc, not eBay). After fitting them, I took the car for a test drive but still have the same issue, despite no DTC codes or warning lights (I have a Topdon scanner).

After reading up a bit more, I learned the Yaw sensor might be involved, especially if it’s been exposed to moisture. As my car has a sunroof I removed the Yaw sensor to check, but the area was bone dry, with no corrosion on the connectors.

I also checked the turbo boost hoses for any leaks to rule that out as the cause of power loss. Next, I decided to pull ABS Fuses 1 & 2 from under the hood to isolate the ABS system. As expected, I got a brake failure message, but surprisingly, the car had full power restored and felt more responsive than usual. I've also had a pull to the right under braking (same side as the sensor and ABS ring I replaced today) since buying the car, but with the ABS fuses pulled, this was hardly noticeable on my test drive.

After a 20-minute run, I reinstalled the ABS fuses and tried again. Immediately, the car went back into power loss / limp mode with the ABS pump activating, and for the first time, the yellow traction warning light (bottom right) was flickering. A scan then returned two new codes:

940F Brake Pedal Sensor
A01F Vehicle Speed Signal (VSS)

This is the first time I’ve seen these codes. I’ve done some searching but can’t find much information on whether these codes might be connected to the issue I’m experiencing. Has anyone dealt with something similar or could point me in the right direction? I’m hesitant to replace parts based solely on codes since I know they don’t always identify the root cause.

Thanks in advance for any guidance!
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Old Oct 28th, 2024, 22:05   #2
SteveDuNord
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I was experiencing pulsing and the car pulling to one side under braking. Changing front discs and pads cured it. I did the rears later.

I'm still getting brake pedal sensor error codes and traction warnings in dash. The pedal sensor is easily accessible under the bonnet - stuck to the brake booster. I'm going to replace mine.

As per this video except ours is on the other side and you don't need to remove the strut brace thingy.

https://youtu.be/PTeH-H5VAYA?si=7a4HyTZQi58S1c6K
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Old Oct 28th, 2024, 22:45   #3
Lancee
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Quote:
Originally Posted by Mark101 View Post
I'm hoping for some help in tracking down a power loss / limp mode issue that also seems connected to the ABS system.

A couple of days ago, the "Anti-Skid Service Required" message appeared again. Since buying the car in March, I've seen this message pop up a few times. It’s never affected the car’s performance, so it’s been on the “get to it when I can” list, almost like an old friend checking in.

The other night, just as I was arriving home, the anti-skid message appeared again. I parked the car as usual and thought nothing of it. However, the next day, as soon as I reached the speed where second gear would typically engage, the power suddenly cut. The car still moved, but I could feel the ABS pump engaging and pulsing through the pedal.

I scanned for codes and found a mechanical error related to the front-right sensor. I removed the sensor and noticed signs of wear on the end, likely caused by a rusted and expanding ABS ring. Under the car, I found a large chunk missing from the ring, which made sense as to why the car couldn’t accurately detect the wheel’s rotation, potentially leading to the power loss and ABS fit.

Today, I replaced the ABS ring and sensor (using mid-range parts from Auto Doc, not eBay). After fitting them, I took the car for a test drive but still have the same issue, despite no DTC codes or warning lights (I have a Topdon scanner).

After reading up a bit more, I learned the Yaw sensor might be involved, especially if it’s been exposed to moisture. As my car has a sunroof I removed the Yaw sensor to check, but the area was bone dry, with no corrosion on the connectors.

I also checked the turbo boost hoses for any leaks to rule that out as the cause of power loss. Next, I decided to pull ABS Fuses 1 & 2 from under the hood to isolate the ABS system. As expected, I got a brake failure message, but surprisingly, the car had full power restored and felt more responsive than usual. I've also had a pull to the right under braking (same side as the sensor and ABS ring I replaced today) since buying the car, but with the ABS fuses pulled, this was hardly noticeable on my test drive.

After a 20-minute run, I reinstalled the ABS fuses and tried again. Immediately, the car went back into power loss / limp mode with the ABS pump activating, and for the first time, the yellow traction warning light (bottom right) was flickering. A scan then returned two new codes:

940F Brake Pedal Sensor
A01F Vehicle Speed Signal (VSS)

This is the first time I’ve seen these codes. I’ve done some searching but can’t find much information on whether these codes might be connected to the issue I’m experiencing. Has anyone dealt with something similar or could point me in the right direction? I’m hesitant to replace parts based solely on codes since I know they don’t always identify the root cause.

Thanks in advance for any guidance!
If I were in your shoes if possible I would swap the sensor with the other side to see if the fault moves.
I perceive that when dealing with sensors, no Volvo OE can sometimes cause problems.
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Old Oct 30th, 2024, 21:43   #4
giw12
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I had exactly the same problems on my 55 plate. My indie immediately diagnosed a faulty CEM and this was indeed the problem.

He sorted it out with Lukasz at Volvo Diagnostic so you could go to him directly I’m sure.
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Old Oct 30th, 2024, 23:31   #5
Mark101
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Quote:
Originally Posted by SteveDuNord View Post
I was experiencing pulsing and the car pulling to one side under braking. Changing front discs and pads cured it. I did the rears later.

I'm still getting brake pedal sensor error codes and traction warnings in dash. The pedal sensor is easily accessible under the bonnet - stuck to the brake booster. I'm going to replace mine.

As per this video except ours is on the other side and you don't need to remove the strut brace thingy.

https://youtu.be/PTeH-H5VAYA?si=7a4HyTZQi58S1c6K
Thanks for the advice. Changing the breaks is definetly on my list to do. But I dont think it is the cause of the issue I have right at this moment.
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Old Oct 30th, 2024, 23:32   #6
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Thats an Idea, I dont hold up hope as I had the issue before I fitted the new ABS Sensor. but it Can't hurt to try.
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Old Oct 30th, 2024, 23:36   #7
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Quote:
Originally Posted by giw12 View Post
I had exactly the same problems on my 55 plate. My indie immediately diagnosed a faulty CEM and this was indeed the problem.

He sorted it out with Lukasz at Volvo Diagnostic so you could go to him directly I’m sure.
Thanks for that. The CEM was a suspect since I read it’s the main connection between most of the modules. So far, I’ve found that the gearbox isn’t receiving a signal from the BCM, even though the BCM passes the scan check with no errors. The fact that you mentioned having the same issue, and that the CEM was at fault, makes it seem like the most plausible thing to check next.
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Old Nov 3rd, 2024, 14:22   #8
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I decided to bite the bullet and pull out the CEM this weekend to check for any signs of water damage. I’m pleased to report that all connectors were clean and dry, with no sign of water ingress. While I had the unit out, I also took the opportunity to clean the pins.

After reassembly, I’m still facing the same issue: power loss above 5 mph, the ABS pump activating, and the traction control light flashing. However, there are no DTCs or error messages on the display.

I recently discovered my Top-Don has live data monitoring, so I checked the BCM while trying to drive the car. The first thing I noticed is that all wheels register a speed of 0.68 km/h when the car is stationary. Once I start moving, as soon as the car reaches about 10 km/h, all wheel speed sensor values shift to "N/A" until the car slows down again. I also noted that the new ABS sensor I fitted lags significantly compared to the other three wheel sensors.

Still scratching my head here, with no clear idea of where to go next!
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Old Nov 3rd, 2024, 14:23   #9
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Would you be able to send the the contact deatails for the Indepentant you used? Many thanks.
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Old Nov 3rd, 2024, 15:40   #10
Lancee
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Quote:
Originally Posted by Mark101 View Post
I decided to bite the bullet and pull out the CEM this weekend to check for any signs of water damage. I’m pleased to report that all connectors were clean and dry, with no sign of water ingress. While I had the unit out, I also took the opportunity to clean the pins.

After reassembly, I’m still facing the same issue: power loss above 5 mph, the ABS pump activating, and the traction control light flashing. However, there are no DTCs or error messages on the display.

I recently discovered my Top-Don has live data monitoring, so I checked the BCM while trying to drive the car. The first thing I noticed is that all wheels register a speed of 0.68 km/h when the car is stationary. Once I start moving, as soon as the car reaches about 10 km/h, all wheel speed sensor values shift to "N/A" until the car slows down again. I also noted that the new ABS sensor I fitted lags significantly compared to the other three wheel sensors.

Still scratching my head here, with no clear idea of where to go next!
And you tried swapping the sensors to see if the fault moved ?
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abs, anti skid, brake issue, power loss, xc90


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