More on 2004 Quest transmission--need some advice

[cleeland]

Oh great Nissan Online Mechanic,

You may remember me posting awhile back about problems with a 2004 Quest transmission (old post ). I haven't given up.

I had also posted about this at the Edmunds Town Hall Forums, and a week ago somebody posted that not only had they had similar symptoms, but that they were able to take the car to the dealer while it was happening, and the dealer was able to diagnose and fix it.

I spoke with the service manager from the repairing dealer this morning and he told me the following:

1. no "CONSULT" codes were found ("P0000")
2. the following codes (from where?) came out: 31 0 36 - CK 600
3. result code vehicle speed sensor automatic transmission
4. result code vehicle speed sensor "NTR" (I don't know what "NTR" is)
5. it was starting in 3rd gear under failsafe mode[/list=1]
   
   I know what they finally replaced, but I was hoping that somebody could help me understand what was pulled enough so that I could describe it to my local dealer. I'd also be iinterested in knowing if the diagnosis/parts replacement concurs with what they actually did. If the codes that he told me aren't "CONSULT" codes, then what are they, exactly?
   
   Finally, is there ANY way for me to investigate any of this stuff myself, or is there any way that I might be able to try to induce the problem based on what was pulled here?
   
   Thanks for ANY help you can give.
   
   -cj

[NISTECH]

The best I can decifer out of what you posted[as its not exactly clear what he told you] It sounds like it had a CAN communication code the CK600 appears to be something you would see in CAN diagnostic flow. What that means if i interpited it right is a line going to a specific control module from another had no communication when it expected to see it which resulted in the failsafe condition of 3rd gear start. It appears the unit that did not transmit the information on the network was the speed sensor [speedometer or unified meter] I am not clear on what NTR stands for as I havent heard that abbreviation before. It is likely for the transmission revolution sensor used to compare vehicle speed to trans speed. perhaps it sent a garrbled signal and initiated the failsafe. if that were the case the only way I think you could initiate the failure would be to be driving down the road and drop it to nuetral and back into drive a few times but that may only put it in fail safe simply because you confused the TCM and not neccesarily set off the failure.

[cleeland]

Wow! Thanks for the excellent response.

The dealer replaced the TCM in this case.

What's interesting is that yesterday I got email from the van's owner and he said that the symptom repeated--even after having the TCM replaced. So the TCM wasn't a fix.

To me, that's good information, since (unless both TCMs share the same problem) it eliminates one more thing that it *can't* be.

Thanks for the tips on not reproducing the problem. Too bad I can't get in and figure out how to jiggle the wiring from the speed sensor while I'm driving.

Is it me, or is the CAN bus more diagnostic trouble than it's worth? Good in theory, but hard in practice...

Thanks again,-cj

[NISTECH]

It is very difficult for even some good nissan techs to figure out. But once you understand the system It is relitively simple. It is mearly a network of 2 wires, its the finding out where in those 2 wires the problem is. All the control units are on those 2 wires to btw so the unit it self could be the problem.

I wouldnt of gone for the TCM in the case you mentioned since the speed sensor was involved in the problem. The speed sensor is responsible for communicating its signal all over the network. The ECM uses it for load inputs to determine fuel ratio and since the cruise control system is now housed in the ECM it is used for that as well. The TCM uses it to control shift points. Heres the kicker, Believe it or not the speed signal is sent to the speedometer from the ABS control unit. The speed signal is a averaged number from all 4 wheel sensors for the ABS. The ABS figures this number and sends it to the speedo and then it is distributed from there.

[cleeland]

Quote » I wouldnt of gone for the TCM in the case you mentioned since the speed sensor was involved in the problem. The speed sensor is responsible for communicating its signal all over the network. The ECM uses it for load inputs to determine fuel ratio and since the cruise control system is now housed in the ECM it is used for that as well. The TCM uses it to control shift points.[/quote]TCM certainly seemed odd to me as well.

Where is the speed sensor located? I presume it takes its speed reading off the transmission and is calibrated to wheel size? Is it any place that I could easily get to it and verify that it's connected properly?

On startup, does something "ping" every item on the CAN bus to insure that it's there and operating? If so, are there timing constraints for responding? It seems possible that under certain conditions the speed sensor might not be responding quickly enough or the signal is lost or stomped on by another sender, and thus the TCM can't see it and drops into failsafe mode. Does that sound plausible?

Quote »Believe it or not the speed signal is sent to the speedometer from the ABS control unit. The speed signal is a averaged number from all 4 wheel sensors for the ABS. The ABS figures this number and sends it to the speedo and then it is distributed from there.[/quote]That's bizarre! Does that mean that there's an easy way to change wheel sizes and recalibrate the speedo, i.e., by using a computer at a Nissan dealer? On all my bicycle computers, you have to tap in the circumference in millimeters; it would be really nice if you could do something similar for cars so that you could use whatever wheel/tire combinations you wanted (as long as offsets are correct, of course).

Based on the information you've seen, you don't have any further ideas, do you?

[NISTECH]

the speed sensor ,by ESM description, is the speedometer/unified meter. No it does not take the road speed of the vehicle from the transmission at all. Like I said it gets it from the ABS wheel sensors. It averages out the speed of all 4 wheels in the ABS module to determine the vehicles speed.

No it does not "ping" the system. It is in constant communication any time the key is on. It constantly sends information from one control unit to the other to make the vehicle operate properly. If one of those messeges is sent out on the communication line and the unit thats suppose to use it does not respond back with the proper response it throws a CAN code in the module that sent the info out.

No there is no calibration procedure at the dealer but there are shops that can calibrate the speedometer/unified meter for tire size changes. That is generally an aftermarket operation as nissan does not endorse doing that. They are very narrow minded about that type of stuff and pretty much say if you make changes to your car like that you void the warrenty on the effected components.

Based on what you gave me I would say one of 2 things could be the problem. either The speedometer/unified meter has a problem or the revolution sensor in the trans has a problem.