[2006silverrr]

Hi, I have been having an intermittent problem over the past few months with my 2006 4.2 Range Rover L322 Supercharged with the ZF 6HP26 Transmission. The car has around 147,500 miles on it, with the original transmission. I first noticed this fault in April, so 4 months ago. The first time the P0705 fault happened I hit a manhole cover that jarred the car around a bit and it threw the car into fault mode. After this first incident, I had no trouble for a month or so and then slowly the fault has occurred more often. Now if I drive the car 2 miles it will go into fault mode. It is completely random when it goes into fault mode. I have been parked, sitting at a light, slowly accelerating, or flooring it and it has gone into fault mode in all different instances, but not every time. It seems to have no pattern as to when it happens.

When it's in fault mode, the indicator on the dash disappears and it slams the car into 3rd gear only. I then have no control over which gear I am in as the shifter does not do anything at this point. I can shift into P, R, N, and D but it slams into gear when doing so. The shifter light next to the shift knob is still illuminated when this happens. I have also noticed that my reverse lights now flicker and do not stay on the whole time while I am in reverse anymore. I switched them to LED's over a year ago. I don't know if this has anything to do with the P0705 but I have read about issues with the reverse lights with the P0705 fault.

I took the car to the dealership and they quoted nearly $10,000 for a complete transmission swap. I think this is absolutely ridiculous as my transmission seems perfectly fine other than the transmission fault issue. I am now thinking about doing this job myself. Would it be possible to clean the contacts on the mechatronics unit and fix the issue that way? Or would I be better off replacing the mechatronics unit? I have read that the mechatronics unit has to be recoded to the car/transmission if replacing. Would I be able to take it to the dealership and have them recode it after replacing or can I recode it myself? Also if you have successfully solved this fault can you give a parts list as to what I will need to order to do this job? If I can fix the mechatronics unit I would also assume I'd be smart to change out the solenoids and all of the seals while I am inside the transmission/working on the valve body.

I would like to know if anybody has any insight into this problem or if anyone has experienced this fault code before on this transmission and fixed it successfully. Any help would be greatly appreciated.

 

[MARK_C]

Dash display is controlled by the mechatronics unit inside the transmission they are electronic data sent over one of the CAN Buses to the instrument cluster, the lights next to the shifter are controlled by the position of the shifter and is purely mechanical controlled by switches on the shifter base. I think I would check the elelectrical connector on the passenger (right) side of the transmission to make sure it was tight and none of the wires appear damaged, then maybe try readjusting the shifter linkage down at the transmission end of the cable to make sure its not out of adjustment, but I think you have an electrical issue between the mechatronics and the IPC.

 

[2006silverrr]

I will definitely check those when I get under the car and start taking it apart. I am also leaning towards an electrical issue in the mechatronics unit. I was wondering if it is possible to ship my mechatronics or TCM out to one of the companies who repairs them. Would they be able to fix my old unit or would I need to buy a new one? I know that the new one would have to be reprogrammed. I saw a company who can copy the old TCM to the new one if you ship them both units. Would this be a good route? Wouldn't the dealership have the tools to reprogram the mechatronics unit if I replaced it with a new one? I have also seen the PRDNL slider for sale on ebay. Would I be able to just change out that part on the mechatronics unit? It looks like it would be possible to just change the PRNDL slider, but I am not sure if that would mess with the electronics in any way.

 

[RRPhil]

The various components that make up the electronic module of the Mechatronic unit aren’t connected together using wires. Instead, the conductors are continuous thin plates which are fastened with tiny spot welds or mechanical swaging. This theoretically makes the assembly more reliable (Ha!).

It can therefore be challenging to replace any of the components as they were never designed to be separated. This company in Bulgaria offer an international service for replacing the inhibitor/gear position switch:
Automatic transmission

Phil

 

[MARK_C]

I'm thinking its a wiring issue on the outside of the transmission, you hit that manhole cover and jarred something loose, or maybe knocked a harness up against something and eventually it rubbed thru and now is an open or short. The mechatronics should be able to take alot more abuse than hitting a manhole cover, or pothole. Check around the outside before digging into the inside. Check that the connector to the transmission is tight and the connections inside it are clean.

 

[2006silverrr]

Okay, I have emailed softelectronics and another company called valve bodies UK. I am leaning towards the valve bodies UK company as they seem to be more helpful and it seems as though this is what they specialize in doing. They said they could source a new valve body from ZF but it would have to be reprogrammed. Would reprogramming be a big deal or would I be better off fixing my valve body that is already programmed to my car?

I would agree that it seems as if it could be a wiring issue. The only thing that doesn't make sense to me is if it was a wiring issue, I don't think it would keep getting progressively worse. I also took it to the dealership here originally and they inspected the transmission and they said that it was likely due to the valve body. The last couple of times I drove it, It wouldn't shift into reverse. I had to move the shifter back and forth a couple times for it to finally slam into reverse. Wouldn't a code reader detect a short? I have used mine before and it showed that I had an open circuit or short for one of the window wires.

It just seems to me that the car is slowly losing communication with the mechatronics unit. Since it slowly has gotten to the point where the car refuses to drive right. Also the p0705 code states that it is receiving a low input from the mechatronics unit, which would also point towards that being the problem. Would it be worth a rebuild of the valve body and the solenoids? My car has 147,600 miles at this point so I'm assuming that rebuilding the valve body wouldn't be a bad idea. I did notice that it was starting to shift worse, mainly the rpms surging when shifting from 3-4 and a hard 2-1 downshift sometimes, which I know is a common problem.

Phil
I have read some of your other transmission threads about teardowns and such but I don't think I saw any part numbers for the seals and the jump tubes. You also stated to wear a ground strap when handling the valve body. Do I need to wear a ground strap while handling the valve body? Which ground strap would you suggest getting?

 

[2006silverrr]

I got the car jacked high enough to get underneath it and took a look. The only thing that I could see on the outside was that a tiny rock got wedged between the wires on the connector. I couldn't see much that looked bad. I drained the fluid and pulled the pan off. There was no metal on the magnets so I don't think there is too much wear on the transmission. I previously had it serviced around 90-100k miles. Which is around 50k miles ago. I am going to let all of the fluid drip off the valve body before taking a closer look at it tomorrow. I will also check the wires on the connector on the outside of the transmission to see if they all look okay.

I am still wondering if I need to buy a ground strap before removing the valve body, as I do not want to ruin any of the electronics.

I did notice that the shifter cable was in the right spot on the mechatronics unit while under the car. So I am still leaning towards the unit being bad. I have stumbled upon other forums where this was also the case with the p0705 code. Either way at this point I will be sending out the valve body to get the mechatronics tested/repaired and all of the solenoids replaced.

Here are a couple pictures of the valve body with the pan removed. I don't see anything that looks wrong but maybe it will help.

 

[2006silverrr]

So I did find what looks like a problem with my connector.

the sleeve in pin 15 is missing it looks like. What does this pin control on the car and is it supposed to be missing? Could this be my problem?

 

[2006silverrr]

I just realized pin 8 is also missing. I don’t think it’s supposed to be like that as the mechatronics unit has 16 pins. I looked at the mechatronic unit connection and don’t see the sleeves for those pins so I’m not sure where they would go. Any help on what those pins go to specifically on this car?
here’s some pictures of the mechatronics connector off the car and the valve body.

 

[MARK_C]

15 is a spare pin, 16 is a ground.

 

[2006silverrr]

Okay thank you for that. So that means it’s not connector issues. I will be shipping out the valve body and mechatronics unit for repair and I will report back with whether that fixes the problem or not