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Discussion Starter #1
I recently installed a rebuilt torque converter in a friend's 2004 RR HSE with BMW transmission. Im a full time mechanic but I've dealt with 2 RR's in my career. Transmission removal, torque converter swap, and transmission replacement went fine. No issues at all. Went to start it and battery was dead. Put it on charge over night. Next morning put fully charged battery back in. Went to start it. Key turned fine but wouldn't crank. Dash lit up. Had full battery power. Just no crank. So I started simple. Found no power to the starter relay behind the battery. I jumped 12 volts to the relay with key on and it started right up. So I was thinking alarm problem. Since it was running I went ahead and topped off the transmission fluid at temp. Went to drive it and it wouldn't shift gears at all. Info center said trans failsafe program. Checked codes got P0705 neutral safety switch. Checked the switch out thoroughly with info from this forum. It checked out in all gears. Checked good also at the connector to the transmission control under the hood. The owner even found a used one for a decent price and thought we would just try it. No change. Code would come back and it stayed in failsafe. And it still will not start with the key either. I'm at a loss. I don't think the trans failsafe is causing the no start issue but could the fact that I'm jumping it to the relay to start it possibly be causing the trans failsafe by not communicating with the neutral safety switch? Why do I keep getting the pO705 when the switch is good? I'm very stubborn and it isn't easy for me to admit defeat. I don't want to take it to a dealer if this is something I can fix without any RR specific software or diagnostic equipment. So if anybody could help a brother out with any kind of idea I would greatly appreciate it. My ideas are running thin. Thanks for reading and sorry for the book I wrote. I just want to be specific as possible.
 

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I know the ECU does not allow the engine to turn over if it does not get signal that the car is in park or neutral. I can’t help but think that the culprit is the inhibitor switch or its lead. It would have been nice if you had access to a diag tool to clear the fault to start out fresh to see if the fault returns when the vehicle is stationary with key in and turned and in park or in neutral. To clarify, did you say that you replaced the inhibitor switch or the transmission control as part of your diagnostics? I lost you there. Also to better understand your issue at hand these are the questions I have I am no expert but I have had my share of problems with this switch on both of my L322. Have you tried putting the selector in neutral and then start it? Does the dash display show PRND light when you move the selector through the gears?
 

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I seem to recall rrphil in one of his very informative editorials saying the transmission valve block module (under car) is programmed to each specific vehicle.

What you need to do is swap out the block from the transmission you just put in with the original one since its already programmed for that vehicle and you will be all set. It has to be the original one , there is an electronic security interphase built in that requires programming. If the original one was not faulty just remove the oNE that came with the transmission and install the origianl one. That will sort it out.CHECK WITH RRPHIL, he's the master with ZF transmissions.
 

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Discussion Starter #4
I would love to hear RRphils input. Ok to the first reply. I do have a scanner. Not RR specific but it does read codes on them and some live data. I've cleared the code several times. Always comes back. I have tested the switch using method from this forum. Opened up the switch just to check. Didn't see any problems. Cleaned it anyways. Re riveted. No change. And yes the owner found a used switch pretty cheap. Installed it. No change. Cleared code but p0705 always comes back. Makes no sense to me. Unless it has something to do with the way I'm starting the vehicle by jumping power to the starter relay because it won't start by the key. It turns.. no crank no start. Plenty of power. Tested charging system. It's fine. I'm at a loss. And to the second reply. I didn't swap transmissions. Only replaced torque converter. Any help would be greatly appreciated. Thanks
 

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LEGACY VENDOR
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As Rovah has already suggested, could you confirm that the gear indicator positions are lit up on the instrument panel and follow the corresponding shift lever position.



Phil
 

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I seem to recall rrphil in one of his very informative editorials saying the transmission valve block module (under car) is programmed to each specific vehicle.
Just to clear up any confusion, when the 6-speed transmission (2006/7) was introduced it featured, for the first time, a valve body assembly with an integrated electronic module (i.e. the mechatronic unit) which incorporated the transmission ECU. This is coded to the vehicle





On the 5-speed transmissions the transmission ECU is mounted on the vehicle so the transmission can’t be coded to the vehicle and consequently both the ECU and the transmission/valve body assembly can be swapped around at will (bearing in mind that the ECU stores the long-term adaptions for the particular transmission that it’s paired with)





Phil
 

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I'm sorry Phil. Which part of that are you saying is my problem? The transmission control module?
The problem is that the PRND are not lit on the dash which means the ECU cant tell which position the gear is in and will not let the vehicle turn over. One, the owner probably bought another bad switch. Or Two, there may be an underlying issue with the electrical wire from the switch to the ECU. Did you make sure the gear rod/cable is correctly installed? If anything I have a working spare switch I can ship to you for testing purpose but you would have to cover shipping back and forth.
 

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Discussion Starter #12
I tested both the original and the new switch using the pin test from this forum. They both tested good. I also checked the connector going into the Transmission control module. Fine also. Would replacing the torque converter reset the adaptations in the TCM? I hate throwing parts but found a used TCM for cheap. It's on its way.
 

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It’s difficult to imagine what could have changed if all you’ve done is swap over the torque converter.

When you removed the transmission from the vehicle did you disconnect the inhibitor switch at the 10-pin plug (C1452 connector) mounted in the bracket on top of the bellhousing and then reconnect it following re-installation, or did you slide the switch off the selector shaft spline, unbolt the bracket from the bellhousing, and let the switch dangle without disconnecting the C1452 connector?

Maybe the problem lies with the connector? Ideally, you would check the wiring continuity for the five inhibitor switch wires right from the ECU C1835 connector to the inhibitor switch (if you have the switch apart).


  1. ECU pin 31 (green wire) to inhibitor switch black wire (+ve feed)
  2. ECU pin 34 (black wire) to inhibitor switch grey wire (L1)
  3. ECU pin 24 (orange wire) to inhibitor switch pink wire (L2)
  4. ECU pin 14 (purple wire) to inhibitor switch yellow wire (L3)
  5. ECU pin 4 (yellow wire) to inhibitor switch white wire (L4)











Phil
 

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Discussion Starter #14
I've actually tested both the original switch and the used switch we put on it. Using those exact instructions that I found on here. They both tested good. So correct me if I'm wrong but if it's communicating from the switch to the connector at the transmission control module but still will not start then it would be a good possibility that the module is bad???
 

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Where the black and grey connectors from the transmission plug into the TCU, is it possible to swap the two connectors accidentally or are they keyed differently? Picture above looks like the keyways are very similar, if so maybe thats your issue.
 

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JACK'S GRANDAD
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I always look at the live data for gearbox position, as well as the dash.
The dash can say nothing at times, but if the ecm is seeing a neutral/park signal it will start.
Hook up and see what the ecm is saying for neutral/park.
If it isnt reading it, it will never engage the starter motor, period
 

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I had the same issue literally month ago during converter swap (my mechanic had). The problem was cracked electrical harness that goes from geras selector switch to gearbox ecu. This harness also combines wires from Oxygen sensors. In our case, lack of selected gears indication was combined with Oxygen sensors errors. Wires shorted and some fuses were blown. This harness is close to the exhaust manifold and insulation goes brittle after years of service. Manipulation during gearbox removal is causing this issue. You need to check and likely fix your wires!

Barted.
 

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It’s difficult to imagine what could have changed if all you’ve done is swap over the torque converter.

When you removed the transmission from the vehicle did you disconnect the inhibitor switch at the 10-pin plug (C1452 connector) mounted in the bracket on top of the bellhousing and then reconnect it following re-installation, or did you slide the switch off the selector shaft spline, unbolt the bracket from the bellhousing, and let the switch dangle without disconnecting the C1452 connector?

Maybe the problem lies with the connector? Ideally, you would check the wiring continuity for the five inhibitor switch wires right from the ECU C1835 connector to the inhibitor switch (if you have the switch apart).


  1. ECU pin 31 (green wire) to inhibitor switch black wire (+ve feed)
  2. ECU pin 34 (black wire) to inhibitor switch grey wire (L1)
  3. ECU pin 24 (orange wire) to inhibitor switch pink wire (L2)
  4. ECU pin 14 (purple wire) to inhibitor switch yellow wire (L3)
  5. ECU pin 4 (yellow wire) to inhibitor switch white wire (L4)










Phil
I have the same problem when i checked for continuity the only one that didnt have it was the purple L3.so do i need a new safety switch?
 

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programmed
The problem is that the PRND are not lit on the dash which means the ECU cant tell which position the gear is in and will not let the vehicle turn over. One, the owner probably bought another bad switch. Or Two, there may be an underlying issue with the electrical wire from the switch to the ECU. Did you make sure the gear rod/cable is correctly installed? If anything I have a working spare switch I can ship to you for testing purpose but you would have to cover shipping back and forth.
  1. I have the same issue with my 03 hse the PRND are not lit. I checked for continuity C1835.jpg the only that didnt was the purple L3 would it be a wiring problem
 

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  1. I have the same issue with my 03 hse the PRND are not lit. I checked for continuity View attachment 284958 the only that didnt was the purple L3 would it be a wiring problem
Means continuity for that L3 is broken somewhere along the line from the inhibitor switch to the ECU. You can easily follow that line and see if maybe it got pinched or chewed up by a rodent. Or maybe at the inhibitor switch connector, the pin slipped out and is not making full continuity.
ECU pin 14 (purple wire) to inhibitor switch yellow wire (L3)
 
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