Automatic transmission shudder during idle, please help!

[AlvinCitroenC5]

Hi all,
I recently purchased a used 2005 Citroen C5 3.0 V6 with the 6 speed automatic transmission. During engine idle while in D while pressing the brake, the transmission (or torque convertor) really wants to pull the car foward, and cause the car to vibrate and feel very rough, thus causing me to place the car in neutral to relieve this issue in the meantime. Because of this I have replace the automatic transmission fluid, but did not resolve the issue. Sometimes when I put the transmission in reverse it little "jumps" and jerk the engine and require significant brake pressure to hold the car so that it does not move. So I replaced the transmission fluid. The old transmission fluid was in poor condition but with no metal shavings that can be seen with the eye. Anyone have a solution or had a similar issue? The idle speed seems normal. Thanks.

[xantia_v6]

Does the engine idle speed seem correct?
Once moving, are all of the gear shifts present and correct?
Have you had the fault codes read from the trasnmission ECU?

[AlvinCitroenC5]

I do notice that the idle speed varies slightly while waiting at different stop lights. When the idle is lower there is less shudder, although at that condition most passenger will not notice, I can still feel it through the steering wheel. And the idle goes slightly higher when I place the transmission in N. Normal upshift is OK. I tried full throttle kickdown on different gear and speed, and 3rd to 2nd is a little rough sometimes, and I tried manual downshift to use engine drag to slow the car down, and 4th to 3rd seems jerky in a way that when during the moment 4th goes into 3rd in manual mode it really jerk/drags and slow the car down. No fault code relating to this. The other, a bad ignition coil, which I have resolved, I went ahead to replace all coils and spark plugs to be safe.

[AlvinCitroenC5]

bump

[Ryan1404]

All engine and gearbox mounts ok?

[AlvinCitroenC5]

They seem ok. It feels like the torque converter really want to grab / have a lower than factory stall speed. And Lexia shows a fault code where it cannot read the VSS signal. Which seems strange as the speedo works. On Wikipedia it states that this transmission (am 6 / TC 80) goes into neutral to save fuel and to reduce vibration. Is thus true in our Citroen? Would a failure to read the VSS cause the tranny to not know that the car has stopped moving while in Drive? Or is my torque converter bad?

[lexi]

Stop lights and brake switch must all be functioning properly. Aisin transmission goes into neutral on a Vel Satis.

[AlvinCitroenC5]

Yes, there is a brake switch fault also. But the brake light does operate. Thus I am baffled as to what that fault means. As the brake light turn on via the brake switch, then why does the ECU/Lexia say there is a fault? Below are the fault codes I currently have.

Thanks.

[xantia_v6]

Modern PSA vehicles have (depending on model and age) either 2 brake switches or a brake switch with 2 sets of contacts. One for the lights and one for the management systems.

[AlvinCitroenC5]

Hi. I just edited my last post with the photos of the fault code. Are you saying that if I crawl under the dash there will be two momentary contact switch? I would go check myself but my 2005 C5 II is actually at the repair shop. And if there are two switches, I just check if both are working correctly? Thank you.

[AlvinCitroenC5]

Bump...