C5 AM6 bad transmission fluid sensor?

[stoilg]

Hi Folks,

I own 2006 C5 v6 Carlsson equipped with Aisin 6 speed transmission (AM6).

After replacing the transmission fluid I reset the adaptations and oil counter. Also checked the parameters just in case and I've discovered that the transmission temp reading is -40 degrees constant. It is not changing at all!!! Tripple checked that using 2 different Lexia and BOSCH scanner as well. Same reading! There isn't any error message recorded.

Since I own the car (6 months now) I noticed that it behaves abrupt when downshifting (3 -> 2 and 2 -> 1) and up-shifting (5 -> 6). Thought that it could be due to old transmission fluid and bad adaptations due to the issues with the engine operation I recently fixed. To be honest its my first car with AT and I don't have experience at all!

Now after the adaptations were reset and fluid replaced its slightly better but still feels abrupt shifting. Maybe the faulty sensor is the cause??

Immediately consulted with a mechanic and he advised me not to drive the car until i get this fixed, as it very likely to cause damage to the transmission. The AT fluid temperature seems to be the most important TCM input value for proper operation.

Anybody encountered such problem? Is the sensor available as a spare part? As far as I understand it is located inside the transmission.

Cheers!

Stoil

[CitroJim]

It certainly looks like the sensor is duff but before condemning it I'd be inclined to check the wiring and everything external that may cause this...

On the HP20, the only autobox I have experience with, the sensor is certainly very internal and part of the valve block loom so I'd expect yours to be the same..

In the HP20 all I understand it does is sense overheating conditions and thi allows the ECU to invoke a set of 'cooling down' maps and stops 'sport' stuff until the temperature is again reasonable...

So, I'd doubt any harm will come from careful driving... I'd not be inclined to drive it too hard in case it's major role is protection...

[stoilg]

"The TCM uses this input along with other sensors input to control transmission operations. When fluid temperature is cold, the TCM will delay (TCC) torque converter clutch operation until the fluid reaches a certain temperature. The TCM will engage the TCC mechanically, connecting the input shaft to the engine in an attempt to cool the fluid if it gets too hot. If fluid temperature reaches a threshold set by the manufacturer; 300° F or so, the TCM will set a fault code and illuminate the MIL to inform the driver. A faulty TFT sensor will affect the torque converter and the transmissions line pressure."

Considering the information above, I'd rather fix that. Broken transmission will cost me a fortune.

[CitroJim]

Oh yes, if that's the case most definitely fix it..

[stoilg]

Hi,
After some proper testing it turned that the transmission fluid temp senor is working fine. So it seems that the current AM6 software version (v0.6) doesn't need the parameter.
Same car, same transmission with v0.9 is detecting the temperature.

Is it recommended to upgrade to the latest available version? I have some abrupt shifting.

Any feedback from people who already did the AM6 software update?

Cheers!

[kaban]

I can confirm that problem is in v0.3 software. After update by Lexia to v0.9 it shows the temperature correctly.