Discovery TD5 auto box problem

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Landrovermad689

Member
Posts
14
Location
Herefordshire
Hi I’ve
IMG_3120.jpeg
just got back into the landrover scene I have a discovery td5 and the gearbox seems to be doing some strange shifting, I’ve had nanocom on it and it’s coming up with code P0721 only every now and then it’ll go into limp mode too with M S lights on it also seems to be revving a fair bit more than I’d like while driving.

I’ve done the obvious filter change and fluid x3 color is fine

Nanocom specifically lists code P0721 downshift safety monitoring I haven’t been able to find out much about it hopefully someone can help me out thanks
 
Stanleysteamer said:
That's a llittle high, could mean the box or the pump to the convertor needs attention. Should be 2600 to 2800.
Click to expand...
Okay where is the pump to converter located? Is it easy to find? It changes into every gear fine including lock up. I will try another stall test later.
EDIT: there are 2 wires with spade connectors underneath near the gearbox one black wire and one green and black near the linkage for XYZ anyone shed some light?
 
Landrovermad689 said:
Okay where is the pump to converter located? Is it easy to find? It changes into every gear fine including lock up. I will try another stall test later.
EDIT: there are 2 wires with spade connectors underneath near the gearbox one black wire and one green and black near the linkage for XYZ anyone shed some light?
Click to expand...
As far as I know the pump is behind the convertor i.e. when you fit the converter it has be ensured that it meshes correctly with the pump, but I think the pump maybe in the box itself.
Like most humans I have never stripped down an auto box. So it would not be get-atable without removing the box, and digging further.
Are the two wires connected to anything or just hanging loose?
When it comes to anything electrical or to do with ECUs etc @sierrafery is the dude!
 
Landrovermad689 said:
the gearbox seems to be doing some strange shifting,
Click to expand...

Landrovermad689 said:
It changes into every gear fine including lock up
Click to expand...
So it shifts strangely but fine.

I think this is an electrical problem althought the stall test is a little worrying.
According to the link it looks like the output shaft speed sensor may be one possibility.
Limp home is the gearbox ecu protecting the rest of the vehicle.
My knowledge of all this is limited so I'll jump off and leave it to those who know more.
Best of luck.
 
Stanleysteamer said:
As far as I know the pump is behind the convertor i.e. when you fit the converter it has be ensured that it meshes correctly with the pump, but I think the pump maybe in the box itself.
Like most humans I have never stripped down an auto box. So it would not be get-atable without removing the box, and digging further.
Are the two wires connected to anything or just hanging loose?
When it comes to anything electrical or to do with ECUs etc @sierrafery is the dude!
Click to expand...
Just hanging loose look like they should be connected somewhere though
 

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Have you driven one before?

If not here goes.

They are not that well controlled, when cold slow to react, the ECU is a bit pants, does get reluctant to change gear. Feels a generation behind the better contemporary longitudinal autos such as the same era GM boxes.

One trick I have is always reverse into the parking spot and drive out, makes gearbox switch errors less likely.
 
MJI said:
Have you driven one before?

If not here goes.

They are not that well controlled, when cold slow to react, the ECU is a bit pants, does get reluctant to change gear. Feels a generation behind the better contemporary longitudinal autos such as the same era GM boxes.

One trick I have is always reverse into the parking spot and drive out, makes gearbox switch errors less likely.
Click to expand...
Yes I’ve driven an auto one before but it was a 300tdi it just seems to be revving too much when in gears when I kick down it seems to struggle which gear to find then m+s flashes that’s when I get the code as soon as I clear it it’s okay until I do it again. I think it’s been remapped as boost pressure is 1.3 bar?
 
Landrovermad689 said:
Just hanging loose look like they should be connected somewhere though
Click to expand...
Right well I'll stick my neck out and ask if there looks like a connector it should/could be connected to. if it will plug in then maybe it should as they tend to make them all so they can only be plugged into the correct other connection. It could be something as simple as the reversing lamp but then that is me thinking old skool as usual!!!
If you have the RAVE manual then the circuit diagrams might tell you.

don't want to put too much in the stew, but this may be worth a read too.
www.landyzone.co.uk

Disco 2 - Checking wiring loom from XYZ switch

I'll be digging into it as soon as I can and will report back. Unfortunately, that's unlikely to be in the next couple of weeks - unless I become tremendously enthusiastic in the evenings - because my weekends are fully booked. However, I am very appreciative of your encouraging words. :)...
www.landyzone.co.uk www.landyzone.co.uk
 
Top two results

carmodnerd.com

[SOLVED] P0721 Code: Fix Output Shaft Speed Sensor Range/Performance Issue Now!

To solve the P0721 fault code, replace the output speed sensor and clear the code using a diagnostic tool. Steps to fix are listed inside.
carmodnerd.com carmodnerd.com

www.e46fanatics.com

PLEASE HELP... P0721 Tranny Fault

Hello all. I think (pretty sure, it's the automatic/ with semi manual option) I have a ZF transmission, and today it threw a code and put me in limp home mode. :banghead: It has only happened this once, and never slips, shifts hard or acts funny at all!!!! I was stopped in traffic, and heard a...
www.e46fanatics.com www.e46fanatics.com
 
Hi the LR description of that code is

"P0721(21)* Downshift safety monitor prevented downshift which would have caused engine overspeed" corroborated with the stall test result above 2800rpm seems very like a clutch slip.... IMO that's what it is, not electrical at all
 
sierrafery said:
Hi the LR description of that code is

"P0721(21)* Downshift safety monitor prevented downshift which would have caused engine overspeed" corroborated with the stall test result above 2800rpm seems very like a clutch slip.... IMO that's what it is, not electrical at all
Click to expand...
Where did you find the LR description of that code as all over the place it comes up with other stuff?

Lets hope this is it.
 
Stanleysteamer said:
Where did you find the LR description of that code as all over the place it comes up with other stuff?

Lets hope this is it.
Click to expand...
In the official workshop manual (named formally RAVE):


AUTOMATIC GEARBOX - ZF4HP22 - 24
DESCRIPTION AND OPERATION 44-19
(second from top):
1700160850350.png



corroborated by the ZF autobox troubleshooting manual so i dont know what "other stuff" did you see:

1700161429037.png


1700161180225.png
 
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