Subaru XV Crosstrek XV - Replace vehicle dynamics control module

Maintenance/Repairs
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1

Hello,

So I took my car in last week to replace my front right axle and fromt wheel bearings. After it was done the car was not drivable, it would brake on its own. The mechanic thought replacing the ABS sensor would solve it, but after replacing the car was drivable but all the dashboard warning lights came on. He suggested I take it to the dealership and have them restart the car’s computer system.

Once I took it to the dealership, they claimed the ABS sensor I just replaced was bad, so I had them replace it. Now they are saying they are receiving an error code and the VDC module needs to be replaced. I have a feeling something’s not adding up, but I’m not sure what to ask/recommend. Any advice?

Here are the technician notes I received:
REPLACED RIGHT FRONT ABS SENSOR & TEST DROVE VEHICLE. UPON TEST DRIVE, TRACTION CONTROL LIGHT STARTED TO FLASH ALONG WITH TPMS LIGHT & SPEEDOMETER WOULD NOT READ CURRENT VEHICLE SPEED. RE-SCANNED FOR DTC’S, FOUND CURRENT DTC:C2521 VEHICLE SPEED ABNORMAL. FOLLOWED DIAGNOSIS TREE, INSPECTED ALL 4 VEHICLE SPEED SENSORS WITH SUBARU SCAN TOOL LIVE MONITOR. FOUND THAT BOTH REAR SPEED SENSORS ARE READING BUT, BOTH FRONT SPEED SENSORS ARE INOP. ACCORDING TO SUBARU DIAGNOSTIC TREE, IT IS NECESSARY TO REPLACE VEHICLE DYNAMICS CONTROL MODULE (VDC) DUE TO HAVING AN INTERNAL FAULT IN VDC ASSEMBLY.

2

When a mechanic starts blaming “the computer”, you know he’s reached the end of his rope.

I’d either get the original mechanic to fix it…or let the dealer fix it.

Good luck.

3

The tech notes indicate to me the tech is most likely following the manufacturer’s service & diagnosis procedure correctly. They’ve used the Subaru pro-level scan tool presumably, & determined the rear wheel speed sensors are registering correctly, but the front wheel speed sensors aren’t. This probably confuses the car’s drivetrain computers to no end. Unless there’s a wiring harness connector that has worked loose, unlikely both front sensors would fail at same time, so replacing the module the sensors connect to (VDC presumably) seems like a good next step. (I presume they’ve hand-rotated the front wheels and verified the signals from the front wheel speed sensors are correct.)

All in all, suggest to accept that the current approach is probably the best one. Ask shop to keep you informed of the fee’s accumulating, b/c at some point you might decide to give up and sell the car to a diy’er who wants one and knows how to fix them.