When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Help - AT Check light, U1000 + U1001 + P1574 codes from hard driving?
'05 G35 sedan AT w/ 152k mi
Hey so I like to drive my car pretty hard but for whatever reason the light & codes in the title come on whenever this happens.
I would normally be concerned it was a transmission problem but the U1000 + 1001 codes lead me to believe its electrical.
The light also ONLY comes on after taking turns at a high speed for >2 miles, NOT when flooring it & driving fast on the highway.
It's extremely annoying as I have to pull over and turn the car off since it locks it in 2nd, 4th, or 5th depending on the speed.
Is it an actual transmission problem? Electrical connections? Wheel speed sensors (P1574 can be that apparently)? ECM/TCM? I'm kind of at a loss. I do have a grounding kit for the car as well.
P1574 is the ECM saying it's not receiving one of the two vehicle speed signals.
U1000 means one of the computers in the car stopped sending data.
Definitely focus on the U1000 first, I suspect it's a TCM issue since it's also gear locking on you. Verify the transmission ground (timing chain cover, on the top, in the middle, two wires landed on bolts, I think it's the one on the right side (when sitting inside the car) is still in good condition and that the lug is wire brushed clean along with the mating surface of the timing chain cover.
If that wire does NOT have part of the bonding kit installed on it then also check the engine main bonding jumper located on the right side of the timing chain cover, larger gauge wire that lands on a 2-hole lug directly below the coolant reservoir.
You would probably know if it was a wheel speed sensor issue because your speedometer would be reading incorrectly. Does this ever happen?
If it's not a grounding issue I would get the car on jackstands and inspect the transmission harnesses just to verify nothing is visibly damaged. Make sure all the wire keepers are properly installed so the wires aren't just dangling and moving around.
P1574 is the ECM saying it's not receiving one of the two vehicle speed signals.
U1000 means one of the computers in the car stopped sending data.
Definitely focus on the U1000 first, I suspect it's a TCM issue since it's also gear locking on you. Verify the transmission ground (timing chain cover, on the top, in the middle, two wires landed on bolts, I think it's the one on the right side (when sitting inside the car) is still in good condition and that the lug is wire brushed clean along with the mating surface of the timing chain cover.
If that wire does NOT have part of the bonding kit installed on it then also check the engine main bonding jumper located on the right side of the timing chain cover, larger gauge wire that lands on a 2-hole lug directly below the coolant reservoir.
You would probably know if it was a wheel speed sensor issue because your speedometer would be reading incorrectly. Does this ever happen?
If it's not a grounding issue I would get the car on jackstands and inspect the transmission harnesses just to verify nothing is visibly damaged. Make sure all the wire keepers are properly installed so the wires aren't just dangling and moving around.
I really appreciate the fast response & advice!
Transmission ground is in good condition & that connection was part of the grounding kit. I installed it after I first had this issue along with shifts seeming slow, forum said the grounding kit could help both & it definitely helped the latter. In fact, I had a previous post (not as much info given though b/c I didn't know as much) where I got told to do the same thing & I did the grounding kit and wire brushing after that!
I believe I wire brushed the main engine bonding jumper but I'll double check in a bit.
The speedometer has never read incorrectly to my knowledge, could the code mean something else then? That code also didn't show up in the normal DTC reading on either app, I had to go to some other menu.
Also got it, are the only potential causes electrical given the symptoms? I love driving hard but if it's potentially an actual transmission problem then I'll obviously lay off. The gear locking scared the **** out of me last night!
I'll check the engine main connector first and then if thats wire brushed I'll jack the car up high enough to have some room to work around with the transmission.
Any possibility it could be an ECM or TCM ground ? Or is the TCM ground just the aforementioned transmission ground? I might be dumb because it wouldn't really make sense for there to be a separate transmission ground but I just wanna make sure.
P1574 is the ECM saying it's not receiving one of the two vehicle speed signals.
U1000 means one of the computers in the car stopped sending data.
Definitely focus on the U1000 first, I suspect it's a TCM issue since it's also gear locking on you. Verify the transmission ground (timing chain cover, on the top, in the middle, two wires landed on bolts, I think it's the one on the right side (when sitting inside the car) is still in good condition and that the lug is wire brushed clean along with the mating surface of the timing chain cover.
If that wire does NOT have part of the bonding kit installed on it then also check the engine main bonding jumper located on the right side of the timing chain cover, larger gauge wire that lands on a 2-hole lug directly below the coolant reservoir.
You would probably know if it was a wheel speed sensor issue because your speedometer would be reading incorrectly. Does this ever happen?
If it's not a grounding issue I would get the car on jackstands and inspect the transmission harnesses just to verify nothing is visibly damaged. Make sure all the wire keepers are properly installed so the wires aren't just dangling and moving around.
By the way - all 3 codes popped up at the exact same time so I do think the P1574 is related somehow even if it's not the wheel speed sensor.
It's just so bizarre its ONLY be during hard driving though if its the electrical connections. Even if its not it's still strange. Gotta love high mileage sports cars.
Also, you seem super knowledgeable so I have two unrelated questions if you dont mind answering: 1. Is a small rattle for the first second or so after starting the engine normal (or at least not concerning)? I've seen conflicting info on whether or not it's just the VVT rattling before it gets oil or if it's actually an issue. 2. This car is pretty high mileage now (153k), but I don't believe it's ever had a transmission fluid change since it's not on the service records but every oil change is. Should I do a drain and fill, flush, or just let it be? Most of the reasoning for not doing it seems like bro science but I don't want to kill the transmission since dropping $2-3k (or ~$1.5k if I do it myself) is an expensive fix for a car only worth $6k. Thanks a lot!
Last edited by connordriza; Jun 11, 2023 at 05:36 PM.
The startup rattle is usually the timing chain tensioner, it uses OIL PRESSURE (not a spring) to maintain tension on the guide, on startup with an engine of that mileage it takes a second longer to build oil pressure so the chain slaps on the tensioner guide. As long as you aren't starting the engine and immediately revving it while it's building pressure you're not going to hurt anything, but it wouldn't hurt to put in a new tensioner to get rid of that annoying rattle sound. Plus it holds better pressure on the tensioner guide throughout normal driving which is always a good thing.
Fortunately the DE engine has a little access plate in the timing chain cover to replace that guide. Definitely look up some videos and read up on how to do it, if you skip a tooth by letting the guide go slack then you will be removing the timing chain cover...
As for the tranny flush, read this post, it will clear up the bro science. I doubt it will fix your issue though.
Is this issue something you can reproduce easily? If so it would probably be best to get a 1 hour diagnostic at Nissan or Infiniti just to verify that it is actually a TCM issue.
