2015 QX70 triggering Limp Mode

D

Dewight Barkley

Member
Car
2015 QX70 AWD
Name
Dewight
Hi all. My 2015 QX70 AWD w/5-speed transmission has recently started triggering the "check engine" light and going into limp mode. She's only at 80K mileage and has had no issues whatsoever other than regular maintenance like brakes and tires. First read of the code said that it was the speed sensor. My mechanic got that part (it was the internal one) from the dealer (almost $200) and installed it. It ran fine for about a week and then suddenly triggered again when I pressed the gas to make a 90 degree turn from a dead stop, almost left me helpless in the middle of a busy intersection. Both times the "check engine" and "IBA off" lights came on in the dash, and the transmission will only shift twice making it hard to get any safe speed over 60. This time the code is directing us to the Transmission Control Module, which I'm being told can only be replaced by replacing the entire transmission valve body. Here's the clincher: I hit a deer about 3 months ago and had most of my front end panels replaced including a few of the sensors that control the headlights, etc, but none that control any engine or transmission function, it was mostly cosmetic with the exception of a radiator mount. I'm starting to wonder if there is any chance the two are related, as I've heard there are a million little electrical glitches that can trigger the car into limp mode. The valve body is a very expensive part, the cheapest I've been able to locate is $1200 (match to my VIN is part # 31705-X600E), I don't want to go replacing this only to get the code again because it's actually being fed faulty information from another part of the car. Does anyone have any experience with this? I've heard that the speed sensor and TCM are both "known issues" with these cars (parts dept even told me "oh yeah, we keep these in stock because we always need one"), but I haven't been able to locate a lot of feeds on here relating to limp mode issues. Any insight, advice, or recommendations on "where to look next" would be most appreciated. Current engine code is PO720, "VSS Signal Low"
 
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Dewight Barkley said:
Hi all. My 2015 QX70 AWD w/5-speed transmission has recently started triggering the "check engine" light and going into limp mode. She's only at 80K mileage and has had no issues whatsoever other than regular maintenance like brakes and tires. First read of the code said that it was the speed sensor. My mechanic got that part (it was the internal one) from the dealer (almost $200) and installed it. It ran fine for about a week and then suddenly triggered again when I pressed the gas to make a 90 degree turn from a dead stop, almost left me helpless in the middle of a busy intersection. Both times the "check engine" and "IBA off" lights came on in the dash, and the transmission will only shift twice making it hard to get any safe speed over 60. This time the code is directing us to the Transmission Control Module, which I'm being told can only be replaced by replacing the entire transmission valve body. Here's the clincher: I hit a deer about 3 months ago and had most of my front end panels replaced including a few of the sensors that control the headlights, etc, but none that control any engine or transmission function, it was mostly cosmetic with the exception of a radiator mount. I'm starting to wonder if there is any chance the two are related, as I've heard there are a million little electrical glitches that can trigger the car into limp mode. The valve body is a very expensive part, the cheapest I've been able to locate is $1200 (match to my VIN is part # 31705-X600E), I don't want to go replacing this only to get the code again because it's actually being fed faulty information from another part of the car. Does anyone have any experience with this? I've heard that the speed sensor and TCM are both "known issues" with these cars (parts dept even told me "oh yeah, we keep these in stock because we always need one"), but I haven't been able to locate a lot of feeds on here relating to limp mode issues. Any insight, advice, or recommendations on "where to look next" would be most appreciated. Current engine code is PO720, "VSS Signal Low"
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I've also had limp mode a couple times with my wife's car. I was told to remove the battery cables and touch them together to reset the computer, which works. That doesn't help with your problem, but might help someone with limp mode .
good luck!
 
It sounds like the issue may not have been repaired the first time. I guess you could clear the codes and see if the VSS signal low code comes back or if it is left over from before the previous repair. It is possible there is a connection issue. I don't know if the VSS connects directly to the TCM inside the transmission or if it connects to an external harness. I would be suspect of grounds and any part of the harness that could have been damaged from the deer hit.
 
Sir I am visiting as I was once a FX50 owner. I would Upgrade your ground wires. My FX50s was doing the same thing for a year and it only Got worse. FLushed transmission, resets, and updates. However when you update your grounds and inspect wires you will detect brittle or weak wires and connection. I purchased a 2013 G37 IPL and the previous owner updated all the grounds. I was like I be damned these cars are known for weak grounds and wires
 
Dewight Barkley said:
Hi all. My 2015 QX70 AWD w/5-speed transmission has recently started triggering the "check engine" light and going into limp mode. She's only at 80K mileage and has had no issues whatsoever other than regular maintenance like brakes and tires. First read of the code said that it was the speed sensor. My mechanic got that part (it was the internal one) from the dealer (almost $200) and installed it. It ran fine for about a week and then suddenly triggered again when I pressed the gas to make a 90 degree turn from a dead stop, almost left me helpless in the middle of a busy intersection. Both times the "check engine" and "IBA off" lights came on in the dash, and the transmission will only shift twice making it hard to get any safe speed over 60. This time the code is directing us to the Transmission Control Module, which I'm being told can only be replaced by replacing the entire transmission valve body. Here's the clincher: I hit a deer about 3 months ago and had most of my front end panels replaced including a few of the sensors that control the headlights, etc, but none that control any engine or transmission function, it was mostly cosmetic with the exception of a radiator mount. I'm starting to wonder if there is any chance the two are related, as I've heard there are a million little electrical glitches that can trigger the car into limp mode. The valve body is a very expensive part, the cheapest I've been able to locate is $1200 (match to my VIN is part # 31705-X600E), I don't want to go replacing this only to get the code again because it's actually being fed faulty information from another part of the car. Does anyone have any experience with this? I've heard that the speed sensor and TCM are both "known issues" with these cars (parts dept even told me "oh yeah, we keep these in stock because we always need one"), but I haven't been able to locate a lot of feeds on here relating to limp mode issues. Any insight, advice, or recommendations on "where to look next" would be most appreciated. Current engine code is PO720, "VSS Signal Low
Sir I am visiting as I was once a FX50 owner. I would Upgrade your ground wires. My FX50s was doing the same thing for a year and it only Got worse. FLushed transmission, resets, and updates. However when you update your grounds and inspect wires you will detect brittle or weak wires and connection. I purchased a 2013 G37 IPL and the previous owner updated all the grounds. I was like I be damned these cars are known for weak grounds and wires
Click to expand...
 
Your issue is eerily similar to my dad's with his Lexus ES350. Heavy Googling led us to discover that many other frustrated ES350 owners experienced the same thing, and had resorted to unplugging their batteries, resetting their traction control systems, and replacing their fuses and O2 sensors, with mixed success.

Refusing to add to the stealership's already deep pockets, we spent weeks approaching the issue from every angle until I decided to drive down to the local auto parts store to buy a can of MAF sensor cleaner. 10 minutes, a clean MAF sensor and a battery reset later, my dad could continue to brag about how his Lexus personifies Toyota reliability.

Here's hoping it goes just as simply for you :)
 
Dewight Barkley said:
Hi all. My 2015 QX70 AWD w/5-speed transmission has recently started triggering the "check engine" light and going into limp mode. She's only at 80K mileage and has had no issues whatsoever other than regular maintenance like brakes and tires. First read of the code said that it was the speed sensor. My mechanic got that part (it was the internal one) from the dealer (almost $200) and installed it. It ran fine for about a week and then suddenly triggered again when I pressed the gas to make a 90 degree turn from a dead stop, almost left me helpless in the middle of a busy intersection. Both times the "check engine" and "IBA off" lights came on in the dash, and the transmission will only shift twice making it hard to get any safe speed over 60. This time the code is directing us to the Transmission Control Module, which I'm being told can only be replaced by replacing the entire transmission valve body. Here's the clincher: I hit a deer about 3 months ago and had most of my front end panels replaced including a few of the sensors that control the headlights, etc, but none that control any engine or transmission function, it was mostly cosmetic with the exception of a radiator mount. I'm starting to wonder if there is any chance the two are related, as I've heard there are a million little electrical glitches that can trigger the car into limp mode. The valve body is a very expensive part, the cheapest I've been able to locate is $1200 (match to my VIN is part # 31705-X600E), I don't want to go replacing this only to get the code again because it's actually being fed faulty information from another part of the car. Does anyone have any experience with this? I've heard that the speed sensor and TCM are both "known issues" with these cars (parts dept even told me "oh yeah, we keep these in stock because we always need one"), but I haven't been able to locate a lot of feeds on here relating to limp mode issues. Any insight, advice, or recommendations on "where to look next" would be most appreciated. Current engine code is PO720, "VSS Signal Low"
Click to expand...
So ive been doing the research on this and the car runs hot and tge transmission heat cycle messes with the wiring of the TCM. This is located inside the valve body. Infiniti has you replacing the whole valve body when you jusy need to replace the TCM. Some say you can do the work yourself and even solder the wire to not have to spend anything. Unless if they find something to make it run cooler this is going to continue to happen. Anyway, not sure if infiniti sells just the TCM component so if theydont they say to take it to transmission shop and tell them you need a new TCM or replace that which is inside the valve body. Saves you thousands and takes about 2 hours to do the work. This is for code P0720. Im going to try to solder mine today and ill let you know if that works!
 
They do not sell the TCM by itself. Wherever there is code P0720 and the car won't shift past 3rd gear, limp mode, etc. the entire valve body has to be replaced. I just had this happen to me in early June of this year. I have a 2015 with 77,000 miles on it. I did all the work myself and the parts alone ran me $2,300 total as I went with an OEM valve body programmed from the dealership for my VIN. You don't want to mess around with used or eBay on this one. The TCM has to be programmed specifically to the car and the exact time/year it was made. You can't just throw in another one from a QX or FX or even g37.
 
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