Is my Transmission Failing

Paul1234002 · Sep 2, 2017

I have a 2006 L322 AJV8 with a transmission issue. Please see below what is happening.

OK, I have changed the filter and Trans fluid. Magnets were clean and there was no sign or feel of any particles in the old oil apart from it being quite dark.

Since the oil and filter service the car has behaved well, That is until today.

Came to a stop at a set of light, went to go and no drive. Tried it in manual,No Joy. Eventually, it went into a gear and i got home.

Put the diagnostic on and got the following codes:

In the transmission Section.

P0705- Transmission Range Sensor A Circuit (Park, Reverse, Neutral, Drive Low Circuit)

In the Engine Section.

P0851- Park / Neutral switch input Circuit Low
U0167- Lost Communication with Vehicle Immobiliser Control Module
U0402- Invalid Data Received From Transmission Control Module

I have checked the battery voltage, 12.4v without engine running & 14.5 when vehicle is running.
Can anyone shed any light what could possibly be wrong. Do i have an electrical issue? or is it something else.

Bobdog · Sep 2, 2017

Paul1234002 said:
I have a 2006 L322 AJV8 with a transmission issue. Please see below what is happening.

OK, I have changed the filter and Trans fluid. Magnets were clean and there was no sign or feel of any particles in the old oil apart from it being quite dark.

Since the oil and filter service the car has behaved well, That is until today.

Came to a stop at a set of light, went to go and no drive. Tried it in manual,No Joy. Eventually, it went into a gear and i got home.

Put the diagnostic on and got the following codes:

In the transmission Section.

P0705- Transmission Range Sensor A Circuit (Park, Reverse, Neutral, Drive Low Circuit)

In the Engine Section.

P0851- Park / Neutral switch input Circuit Low
U0167- Lost Communication with Vehicle Immobiliser Control Module
U0402- Invalid Data Received From Transmission Control Module

I have checked the battery voltage, 12.4v without engine running & 14.5 when vehicle is running.
Can anyone shed any light what could possibly be wrong. Do i have an electrical issue? or is it something else.

what mileage was it when you changed the oil and filter and is it the GM gearbox, same as the TD6?

Paul1234002 · Sep 2, 2017

Bobdog said:
what mileage was it when you changed the oil and filter and is it the GM gearbox, same as the TD6?

Mileage was 124500. and its a ZF6 box.

Bobdog · Sep 2, 2017

Paul1234002 said:
Mileage was 124500. and its a ZF6 box.

the GM boxes (and i suppose the ZF6) are supposed to be sealed for life but apparently if they are not serviced by around 70k, the oil starts to burn, resulting in damage to the gearbox. apparently many a GM box has died that way. my mate just found out the hard way, his had done 96k when the gearbox died.

Bemble · Sep 2, 2017

I’ve seen this P0705 error reported a few times on the 6HP26 but nothing conclusive yet seems to have emerged as to the cause.

The earlier 5-speed ZF unit had an external inhibitor switch which used five metal fingers to wipe across contacts to generate the control logic signal.

Inhibitor%20switch%20wiper_zpsvupuao81.jpg

This design is prone to problems and P0705 errors are quite common with the 5HP24. Clearly the switch can simply be replaced to rectify.

On the 6HP26, ZF changed the design completely to a ‘non-contact’ slider in the electrical/electronic part of the Mechatronic unit that appears to use magnets laid out in four strips to generate the logic of signals (Hall effect?) so that the transmission ECU knows the position of the manual valve and selector.

It’s pretty hard to see what could go wrong with this. Filthy oil depositing a layer of signal-blocking material across the face of the slider maybe?? Unlikely, I suppose. An issue with the Mechatronic unit itself, perhaps? I’m very interested to hear how you get on with this as I suspect it’s going to become a more common issue as these transmissions age.

Sorry I can’t be of any help.

Phil

Paul1234002 · Sep 3, 2017

Phil,

Thank you for your very detailed response.

Does this require a rebuild or a new gearbox?

Bemble · Sep 3, 2017

I really don’t think it’s as serious as that. Worst case scenario would be a replacement Mechatronic unit (coded to the vehicle) and these can be removed from the sump so there’s no need to remove the transmission from the vehicle.

The 6HP26 is a pretty rugged and durable transmission so I wouldn’t give up on it just yet.

A very common fault with this particular transmission in the L322 is the selector cable clamp bolt seizes up (through corrosion) in its hole in the selector lever. This prevents it articulating as the lever moves through its arc and causes the lever to be slightly out of position relative to the shift lever. It’s definitely worth checking that the clamp bolt is moving freely (and it’s also an opportunity to lubricate it) if there are any issues regarding drive/reverse engagement.

It’s possibly also worth disconnecting the 16-pin connector from the back of the transmission and reconnecting it again, just in case there’s a dodgy connection? (don’t touch the pins, though)

Phil

Paul1234002 · Sep 4, 2017

Phil,

On Saturday prior to your reply, I had lubricated the parts as you described. I was out in the car that evening and drove approximately 10miles. About 10mins into the journey i lost all gears again. I reset it and carried on my way with no issue. I was out of the car for about 2hrs then started on my way home when in less than 5 Mins it went again. As per your recent advise i got under the car and drenched the parts in WD40. I left it to soak for 30mins then smothered the parts in grease.
I have taken the car out tonight for about 20minutes of stop/start (due to traffic) and basically drove it as if i had pinched it. It never once lost gears and it felt that the gear change was quicker. Could this truly be fixed ????????

I will monitor the car over the next week and advise you. I don't normally use the vehicle until the weekends (My little Treat).

Thank you for all the advice given.

Bobdog · Sep 4, 2017

Paul1234002 said:
Phil,

On Saturday prior to your reply, I had lubricated the parts as you described. I was out in the car that evening and drove approximately 10miles. About 10mins into the journey i lost all gears again. I reset it and carried on my way with no issue. I was out of the car for about 2hrs then started on my way home when in less than 5 Mins it went again. As per your recent advise i got under the car and drenched the parts in WD40. I left it to soak for 30mins then smothered the parts in grease.
I have taken the car out tonight for about 20minutes of stop/start (due to traffic) and basically drove it as if i had pinched it. It never once lost gears and it felt that the gear change was quicker. Could this truly be fixed ????????

I will monitor the car over the next week and advise you. I don't normally use the vehicle until the weekends (My little Treat).

Thank you for all the advice given.

quick question, did you get a "trans failsafe prog" message come up on the dash?

Paul1234002 · Sep 4, 2017

Bobdog said:
quick question, did you get a "trans failsafe prog" message come up on the dash?

The only message I had was limited gears

Paul1234002 · Sep 9, 2017

Good afternoon all, Its time for an update.

The car has been stood since Monday night since my last post.
Took the wife shopping this morning travelled about 5miles and all was good. just been on a 35mile round trip and while i was doing approx 20 - 25mile i got a chance to accelerate (When the Saturday driver had moved) when all i got was just revs. I pulled over put the car into neutral then into reverse then into drive. I had no warning messages and normal operation continued for the rest of the journey. I am at a bit of a loss at the moment as Im not 100% sure the problem has gone. Any Ideas????

Paul1234002 · Oct 1, 2017

Good Morning All,

Its been a few weeks and i thought i would give a further update.

I have been driving the car a little more than usual over the past weeks with no issues at all that is until yesterday. I had parked up at a local shopping centre when i got the dreaded bong and the display saying Limited Gears, HDC not working. I switched the car off and re started it and all error messages gone. Locked the car and went about my buisness. When i returned to the car started it, No dreaded bongs but my courtesy light was still on. I switched it off and away i went on my journey without an issue, when i got home i noticed that the folding mirrors were out of sync.

With the mirrors sorted and no other concerns i parked it up for the night. This morning i had popped out and the car drove as it should. Then on my way home i was slowing down at a junction when "BONG" Limited Gears,HDC not working. Luckily i was only around the corner got home and switched the car off and then back on again and there was no errors coming up on the screen.

Has anybody experience similar issues or can any help with this.

Thank you all in advance.

paulh71 · May 26, 2019

Paul

Did you ever get this sorted as mines doing the exact same thing

Thanks

Is my Transmission Failing

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