No fewer than four XC90 owners chime in on this forum thread with the same problem: their XC90 is pushing while they’re at a stoplight or just generally stopped, when the SUV is in Drive and their foot is on the brake.
User klauzon1 issues the definitive answer when he writes …the torque converter of the transmission causing a lower engagement idle (stall speed) than the vehicle was designed for…
Contributor jimmy57 adds That sounds like the TCC (torque converter clutch) is being applied to some degree. The TCC solenoid could cause this as could a problem with the TC flow control valve. TCC is applied by reversing fluid flow through converter that is for cooling.
I have the following problem. When the car is stopped and in gear, it is trying to launch forward (or backward in reverse). It takes a lot of effort in pushing the brakes to keep the car from moving when I’m standing at a red light. No engine fault codes. The engine would sometimes halt at the light or when putting it into “D”. When I put the car from “D” or “R” into Neutral or Park, the RPM jumps up to about 1200-1500 as the there is no more load. The RPM settles in a few seconds. There is no rough idle.
******FIX********Have a 2006 xc90 v8 with identical condition with code p0506 indicating can’t reach target idle. The code after clearing would only return if left in gear with brake held tight. My engine in park was at approx. 700 rpm when in gear with brake tight 500 rpm with the engine trying to drive through the brake. Contacted our local dealer 2 hrs away, asked them to check if the software or transmission are out of wack for this vehicle as it was a recent auction car. 1 week and $250 in diag time the idea was to replace throttle body (est. 900). Due to being used volvo specialized dealer I opted to swap from a known good car. DID NOT CHANGE ANYTHING. I changed out the valve body in the trans due to fact volvos experience heavy wear in the valves of the trans not usually the trans it self. NO CHANGE. Decided to get a used transmission.**********FIXED**********As suspected the problem had nothing to do with the idle condition the problem was with the torque converter of the transmission causing a lower engagement idle (stall speed) than the vehicle was designed for making the engine module think it needed to do all it could to raise the idle. This would be the same as putting in gear, holding the brake and stepping on the gas. Important note:These forums seem to be great at sharing the strange problem modern cars have, yet we have to remember to take as much time sharing the fix as these new vehicles are very difficult to figure out and even the dealers have no idea either. Modern cars are great but we need to have a lot of understanding to survive.