I have a 2007 Pathfinder LE with approximately 120K miles. Recently, the trouble light came on and when I checked the code it indicated "transmission input speed sensor". I took the car to a local mechanic who changed the fluid and replaced the sensor. He told me that there was quite a bit of metal particles in the pan and that the transmission might be nearing failure. He also said not to be surprised if the trouble light came back on with the same code soon after the repair. The service was to change the fluid and clean/replace the filter, no flushing was done. Well, the light came back on the very next day with the same code. I had checked around a little to get an idea of the cost to replace the transmission and got one quote of around $5200 which included a new radiator due to supposedly known problems related to cooling the fluid. Since that amount is in the neighborhood of the current value of the car, I decided to continue driving it around my small local town to see if the shifting would be affected. The only shifting problem I was seeing was a clunk when it shifted into the lowest gear as I decelerated to a stop. HOWEVER, a couple of days ago, I was returning from a short errand and noted that it seemed to be slipping a bit as I pulled into the garage. I turned it off and went into the house. Later that evening I decided to take it for a short drive around the neighborhood to see if the slipping was transient or was now a permanent condition. When I got in the car, the engine would not start. All of the dash lights come on but there is no noise at all when I turn the key to the start position...no clicking or any other noise. I thought that the 3-year old battery might have coincidentally dropped dead so I did all of the normal battery stuff including trying to jump start it from another vehicle. I get nothing when I turn it to the "start" position. It seems like too much of a coincidence to have this no-start problem appear right when I'm having the transmission problem. BUT I'm stumped as to what could be going on with the transmission that would produce this type of problem. Any suggestions on what to look at that could product this condition that could be caused by the transmission?

lilmoose wrote: ↑

Thu Sep 22, 2022 11:18 pm

... I took the car to a local mechanic who changed the fluid and replaced the sensor. He told me that there was quite a bit of metal particles in the pan and that the transmission might be nearing failure. He also said not to be surprised if the trouble light came back on with the same code soon after the repair. ...

The metal particles stuck onto the magnet trap inside the fluid pan is normal unless there are chips of metal, like shown in the picture below. "Not to be surprised if the trouble light came back on with the same code soon after the repair" is a red flag statement in my book when coming from a mechanic that just charged you to replace a sensor that they knew would not fix the problem. Trouble codes for one component can be caused by issues with other components, like the park/neutral position switch in this case for example. I would get a second opinion with complete diagnostics from a Nissan service professional before you start looking at replacing the transmission.

mdmellott - thanks for your feedback. In an effort to troubleshoot the neutral safety switch, I noticed today that when I turn the key to the ON position, I don't see any indication of the shift position (P/R/N/D) on the display. Should this be illuminated when the engine isn't running? I also tried turning the ignition ON, pressing the brake pedal, and shifting to neutral to see if it would start there...it wouldn't. I didn't get much detail from the mechanic about the nature of the metal in the transmission pan. However, I must admit that I had not followed Nissan's recommendation for routine transmission maintenance as this was the first service done since I bought the car and it currently has about 120K miles on it.

Check the TCM fuse, sounds like it's offline. If the fuse is good and has power, your TCM may have given up the ghost and might even be crashing the CANbus and making it unusable for other devices. Unfortunately, that's an infamous tendency of R52 Pathy / D40 Frontier TCM's.

Update - I checked and found the 10A TCU fuse in the box under the hood near the firewall was blown. I temporarily pulled one of the other 10A fuses and installed it in the TCU socket. Voila...the car started right up. I then noted the following: (a) the performance in reverse seems normal, (b) performance in drive is very sluggish. I then turned the ignition off and then tried to restart the engine...dead again. The TCU fuse blown again. IS my goose cooked or is there a possible simple fix?

Cooked. Needs a Valve Body at least, but given the metal your guy found in the pan, my guess is the tranny is shot.

OK. Now I need some advice on what I should expect to pay to have the transmission swapped. I talked with one local shop about the symptoms I was having and he gave me a price to swap the trans and to also install a new radiator. The price seemed really high to me but it may be quite reasonable. The shop involved is a local auto mechanic that specialized in engine and trans work, not one of the national transmission chains.

mdmellott wrote: ↑

Fri Sep 23, 2022 7:51 pm

lilmoose wrote: ↑

Thu Sep 22, 2022 11:18 pm

... I took the car to a local mechanic who changed the fluid and replaced the sensor. He told me that there was quite a bit of metal particles in the pan and that the transmission might be nearing failure. He also said not to be surprised if the trouble light came back on with the same code soon after the repair. ...

The metal particles stuck onto the magnet trap inside the fluid pan is normal unless there are chips of metal, like shown in the picture below. "Not to be surprised if the trouble light came back on with the same code soon after the repair" is a red flag statement in my book when coming from a mechanic that just charged you to replace a sensor that they knew would not fix the problem. Trouble codes for one component can be caused by issues with other components, like the park/neutral position switch in this case for example. I would get a second opinion with complete diagnostics from a Nissan service professional before you start looking at replacing the transmission.

We may deal with the same trans issue on my friend's Pathfinder. 97k miles on the clock so it might be good to get a new trans anyway. The input speed sensor was replaced about 2 months ago and still lit intermittently. It's neat overall with new tires, and brake pads. We'll check the condition of the fluid pan first.

After looking around for new cars I've about decided that I will have the trans swapped. One local shop that I talked with a couple of months ago quoted me about $5200 to swap the trans and install a new radiator. Seems like a lot of money but a second estimate wasn't much different. I will need to confirm exactly what type of repaired transmission he was planning to install (used/repaired/remanufactured). The repair will be in the neighborhood of the current value of the car but if I repair it I can (hopefully) drive it for another year or two. Or, I could still sell or trade it later and recover some of the repair cost.

lilmoose wrote: ↑

Sun Oct 16, 2022 12:23 pm

After looking around for new cars I've about decided that I will have the trans swapped. One local shop that I talked with a couple of months ago quoted me about $5200 to swap the trans and install a new radiator. Seems like a lot of money but a second estimate wasn't much different. I will need to confirm exactly what type of repaired transmission he was planning to install (used/repaired/remanufactured). The repair will be in the neighborhood of the current value of the car but if I repair it I can (hopefully) drive it for another year or two. Or, I could still sell or trade it later and recover some of the repair cost.

If I were a betting man, I would spring for a remanufactured valve body, solenoids and TCM assembly at a cost of about $500, install it myself and hope the clutch packs in my transmission are not shot. If it was mine, I would take that gamble, but that's just me, and it would give me something to do on the weekend for fun.

If I had actually seen the type of metal on the magnet trap when the pan was dropped, I would have a better feel for this bet. Chips of metal: Bye-bye transmission and buy another. Normal particles of metal: I would be all in for a valve body replacement.

Thanks for the feedback. When I had the trans serviced (fluid change, filter, etc.) the mechanic said that there was a "lot" of metal in the pan but I wasn't astute enough at the time to get a better description of the actual particulate size and amount. Any type of DIY work that I do these days has to be done in the driveway and at my age (75+), I'm not terribly motivated to spend a lot of time crawling around under a car. My main goal was to try and better understand what was going on so that I can hopefully avoid being sold things I don't really have to have.