2004 Transmission Question (Manual Shift Mode Behavior)

[Ars Gladius]

Normally when you are in manual shift mode and come to a stop at a light (or whatever reason) the transmission would automatically return to first gear.

For the last few weeks, I have noticed that this is no longer the case on my car. In manual mode if I was in, say, 4th gear and I come to a stop the car stays in 4th gear and does not downshift back to 1st. I have to manually cycle the gears down or return it to auto mode. This is the same for all gears when in manual mode.


The transmission behaves correctly in auto mode. All gear shifts are smooth in both modes with no hangs, slams or stutters.


Any ideas?

[JRL]

That's weird!

[guyeye]

Does the tranny actually stick in 4, or is it just the display? Seems like it would stall out- does it? Or does it seem to go into neutral? Does it seem like you're having any weird torque converter issues? So many questions! Maybe try to describe how it behaves after cruising when you come to a stop, then try to take off again without trying to shift (down, up or otherwise).

[Ars Gladius]

It definitely is still in 4th gear as the display shows. It does not stall (there's a lot of torque in our engines) it's just not very good for the transmission to be in anything other than 1st or 2nd from a dead stop.

City driving, highway driving, it is all the same in manual mode, it will stay in whatever gear you were driving in when you come to a stop instead of going back to 1st. Auto mode is completely normal.

[JRL]

Are you nuts?
They ALL go back to 1st (in manual mode) after you stop and what his is doing is NOT normal

[guyeye]

I might very well be nuts, but I was wondering if it was making any weird straining/torque converter noises when he was stopped. Clearly there is something wrong, but in the interest of troubleshooting, I thought it might be nice to know what the actual symptoms were other than "stuck in 4rth".

As for the problem at hand, I would say this must be some sort of software glitch, as Geartronic transmissions are supposed to function no differently from the automatic mode when coming to a stop (sorry for stating the obvious). It's clearly receiving the correct input to go into Geartronic mode, but it's not processing the engine input signals correctly. See if there are any codes being thrown- It sounds like this is a TCM/software issue. In the meantime, no Geartronic for you!

[JRL]

This I can't answer, I have no idea how that function works, if it's software or hardware, but whatever... yours is not working properly.
Is this doing damage, that too I have no idea.

I'll try to find out some info for you when I go over to my dealer later

[billr99]

According to VIDA, in Geartronic mode, the dash display for gear selected is determined by the circuit board that is housed in the gear selector panel. That is, the panel on the console with the PRND and +/-, right?.

Upon installation of the board, VIDA has a procedure for checking correctness of the display versus the selector state. It reads "Ensure that the letters and/or digits on the display on the combined instrument panel correspond to the shift positions on the top panel." Pretty straight forward and there is no adjustment, etc. Relatively simple R&R for the most part.

So since your tranny seems to be operating properly except for the display, my bet is a bad board. And just like many things Volvo, according to VIDA, you have to buy the whole panel (PN 9463547, 8636212, 30650001, or 8699431 depending on chassis number and interior colour) to get the board. Eire Vo-Vo maybe?

Good Luck,

Bill

[guyeye]

Not if it's ACTUALLY stuck in gear, as he states. But that's very interesting info, Bill!

It does seem like something terrible would happen or there would be a bad BAD sound from the transmission/torque converter if the car was running at a full stop and it was ACTUALLY engaged in 3rd, 4rth or 5th gear! Hence, my "captain obvious" questions.

None the less, as JRL points out; it's all merely speculation until some educated diagnostics are done. Interesting!

[billr99]

Not if it's ACTUALLY stuck in gear, as he states. But that's very interesting info, Bill!

It does seem like something terrible would happen or there would be a bad BAD sound from the transmission/torque converter if the car was running at a full stop and it was ACTUALLY engaged in 3rd, 4rth or 5th gear! Hence, my "captain obvious" questions.

None the less, as JRL points out; it's all merely speculation until some educated diagnostics are done. Interesting!

Yeah, the fact that he doesn't stall seems to me to indicate that he isn't stuck in 4th. These motors have a fair amount of torque but starting off in 4th should be pretty obvious. Try winter mode and you'll see what I mean. 0-60 in the same day sort of acceleration and that's in 3rd. Plus he doesn't indicate that an CEL is coming up which it should. But in any case, a VIDA/DICE hookup should say something and should be the next step rather than trying to guess.

Cheers,

Bill

[Ars Gladius]

As mentioned, it stays in whatever gear that it is in. The acceleration is noticeably retarded, slow as snails. I've been in winter mode before in the past (to see what it did) and it is definitely in a high gear when starting.

Because of the torque converter it is relatively hard to stall out like you would immediately see in a true manual transmission, there is always some slip and I don't push it when this happens. You can start a manual transmission in high gear if you feather the clutch enough (but causing high wear on the friction materials and heat aka "burn the clutch").


When the engine is idling the pump effect is too weak to drive the turbine and the vehicle will not move. As the engine speed (RPM) rises it successively starts to drive in a gradual way. At higher engine speeds (RPM) the power transfer to the turbine can be up to 95%. The torque converter functions as an hydraulic clutch.

When stopped there is very limited coupling in the torque converter, so it doesn't matter what gear the transmission is in as there is almost no power being transferred between the engine and transmission.



DIM gear display is correct on what gear it is in. I can step down the distinct gears from 4th (or 5th or 3rd) to 1st and tell that there are shifts for each step.



The only other thing that I should mention (and I don't recall this starting at the same time), is that the front left ABS wheel sensor is showing a fault (possibly the tone ring according to the DTC code), so the ABS light it on. Some of the car systems depend on the ABS system for wheel speed readings (such as the Haldex coupling). However, the other sensors are fine, the speedometer in the DIM is functioning, and the AWD appears to be functioning as well (though I will have to confirm specifically before stating this with any certainty). I am getting this looked after very soon, so I'll see if this makes the trans issues go away. Also, like I said, the trans behaves itself in auto mode (which would still need speed readings).

[howardc64]

On my 01 T5, I know ABS info feeds into the tranny computer. The tranny had some harder shifts (down? can't remember) when I had the ABS computer out for resolder (01s had circuit board issues). The car is perfectly drivable but I noticed a couple of hard shifts. VIDA says this about ABS info feeding into TCM

Brake control module (BCM) / ABS control module (4/16). Provides information about the vehicle speed and also the difference in speed between the left and right-hand wheels. Prevents upshifting if the difference in speed is above 40 km/h to protect the differential in the transmission.

Don't know why this would happen in manual but not auto mode. Of course, we can't read the TCM software to know what it does.

[billr99]

Ars:

I see where you are at on this now. Looks like, at this point, your only recourse is to get VIDA involved and see what it has to say. I'm still wondering since you say that full auto operation is normal if the Geartronic board isn't the problem. But in any case, hopefully, VIDA will tell you that or whatever is actually out of whack.

Good Luck,

Bill

[hoonk]

Your TCM might be confused about how it is supposed to shift - I would reset the transmission adaptation with Vida - under Vehicle communication, TCM, advanced, resetting adaptation - the TCM will then relearn the best shift pressures.

[Ars Gladius]

Following the BCM sending ABS telemetry to TCM rabbit hole...



The ABS fault only comes up once the vehicle speed is above 40 km/h and the system has run its tests and throws the fault code for the sensor.


So this morning with no ABS fault showing, I put the transmission in manual mode (3rd and 4th) and came to a full stop, transmission returned to 1st gear as it is supposed to.

Drove above 40 km/h to get the ABS fault to trip, I put the transmission in manual mode (3rd and 4th) and came to a full stop, transmission did not return to 1st.


So it does appear that while the BCM/ABS is unhappy, about a single wheel sensor data fault it would seem, it is not passing all the info needed by the TCM for to run in manual mode.

I guess auto mode uses other telemetry points as it works fine regardless of the ABS fault status.

The curious thing is that shifts in both modes work 100% fine, no harshness or delays, it is only the manual mode return to 1st on stop that was wonky.


I guess that answers my original question. Hopefully this is helpful in the future if someone else runs into these stacked fault conditions.

[howardc64]

Following the BCM sending ABS telemetry to TCM rabbit hole...



The ABS fault only comes up once the vehicle speed is above 40 km/h and the system has run its tests and throws the fault code for the sensor.


So this morning with no ABS fault showing, I put the transmission in manual mode (3rd and 4th) and came to a full stop, transmission returned to 1st gear as it is supposed to.

Drove above 40 km/h to get the ABS fault to trip, I put the transmission in manual mode (3rd and 4th) and came to a full stop, transmission did not return to 1st.


So it does appear that while the BCM/ABS is unhappy, about a single wheel sensor data fault it would seem, it is not passing all the info needed by the TCM for to run in manual mode.

I guess auto mode uses other telemetry points as it works fine regardless of the ABS fault status.

The curious thing is that shifts in both modes work 100% fine, no harshness or delays, it is only the manual mode return to 1st on stop that was wonky.


I guess that answers my original question. Hopefully this is helpful in the future if someone else runs into these stacked fault conditions.

Glad you found it and great diagnostic work!!!

[guyeye]

Very interesting indeed!
This has got to be one of the very best automotive forums I've ever belonged to. Bravo!

[billr99]

Following the BCM sending ABS telemetry to TCM rabbit hole...



The ABS fault only comes up once the vehicle speed is above 40 km/h and the system has run its tests and throws the fault code for the sensor.


So this morning with no ABS fault showing, I put the transmission in manual mode (3rd and 4th) and came to a full stop, transmission returned to 1st gear as it is supposed to.

Drove above 40 km/h to get the ABS fault to trip, I put the transmission in manual mode (3rd and 4th) and came to a full stop, transmission did not return to 1st.


So it does appear that while the BCM/ABS is unhappy, about a single wheel sensor data fault it would seem, it is not passing all the info needed by the TCM for to run in manual mode.

I guess auto mode uses other telemetry points as it works fine regardless of the ABS fault status.

The curious thing is that shifts in both modes work 100% fine, no harshness or delays, it is only the manual mode return to 1st on stop that was wonky.


I guess that answers my original question. Hopefully this is helpful in the future if someone else runs into these stacked fault conditions.

Congrats, Ars. And yet another victory for the DIY mechanic/owner!

Cheers,

Bill

[mapper]

[thumbup] Nice work...definitely a nice little tidbit added to the knowledge base!