been debugging a lingering p0720, p1574 on my 03 infiniti i35.
i still have these dreaded codes come up after several hundreds miles even after doing the following:
-replaced the speed sensor with a brand new unit purchased on ebay. after about 500 miles the code came up again
-thinking i had a bad sensor i purchased another sensor, now on brand new sensor #2. this time, the codes didnt come up for at least a couple thousand miles
-realized during this time my +battery terminal ring was broken, resulting in an intermittent connection to the battery. i only realized this after one morning the main relay was clicking constantly. popping the hood, i discovered the broken ring on the + cable. i was hoping this was the issue that has plagued my car w/ these trouble codes. wishful thinking, now after 200-500 miles the same two codes are triggered. things are good until the computer goes into limp mode after the A/T light flashes and/or CEL is on.
-some misc things ive tried during this period w/ no luck:
verified the related fuses are ok, probed out the VSS harness. i get continuity on all 3 wires from connector to connector.
cleaned the transmission ground strap and ensured there is a good connection to the chassis and transmission.
i also cleaned the connectors and ensured the harness connector and connector to the VSS are seated snugly. also cleaned both battery terminals.
i also probed the resistance of both of the sensors. interesting i get open circuit when i probe the different combinations on the 3 sensor terminals.
in an unbiased state what is the expected impedance and is there a simple test using a multimeter to verify if a sensor checks out ok?

im totally lost on whatever else i can try so any help is appreciated. i may try another vSS sensor but this time sourced from the nissan dealership. previous sensors appeared to be aftermarket so im not sure if this has had an effect on these codes?
if the TCM is bad would i expect to see codes other than p0720 and p1574?

 

i replaced the sensor with a new genuine factory piece and after 200miles, the AT light started flashing. same p0720, 1574 codes came up. im at a loss on what else to check and now considering bringing it to a dealer so they find out if this is a TCM issue or wiring related issue.

has anything had a bad TCM be the cause of these codes? seems that the majority have fixed these codes by replacing the revolution sensor.

 

Search my others posts on this site. I chased mine for 6 mos. Remove instrament cluster and tighten all screws on cluster. Now fixed

 

this post is to add positive reply to the repository of knowledge here on Maxima .org about VSS and TCM issues..

I had the same problem where my Cruise Control went out and I was having a P0104 and 0504, VSS and TCM Trouble code. I went to the local Autozone, had the code scaned and they recommended to replace the VSS as many members here have done. However, after replacing the VSS 3 minutes down the road the 0104 and 0405 returned.

Looking at this post and the other posts about VSS main thread I decided to re-solder the points on the instrument panel but soon realized I didn't have soldering tools.

So, instead I cleaned the printed circuit board contacts, screws, and washers around the speedo and I clean the contacts on the printed circuit board around the main connectors. Installed it and my cruise control returned the VSS and TCM trouble codes went away!

So, before you buy a VSS, re-solder the Speedo, or do any deep work to solve the issue just clean off the contacts around the screws and around the printed circuit board connectors first. Then go from there