I noticed that is almost no information about the ZF5HP24 Input and Output Sensors located in the valve body part of the transmission.
Our Indy mechanic remarked that we might need to replace one of these transmission sensors (input or output - he did not say which one).
3 weeks ago, We went to a department store that just had their parking repaved earlier in the day (hot asphalt and temps in the upper 80s').
After I started the engine, it began to feel like it was going to stall (also when I tried to accelerate, it went into restricted performance - limp mode).
My code scanner (I keep in the center console) gave me a P1121 DTC code and for some odd reason I could not erase it. We drove to our indy mechanic in limp mode (only about 5 miles away).
He was able to run his scanner and found a problem with the transmission speed sensor, then he erased the DTC codes and everything was back to normal. He wants to wait to see if this is an recurring event.
Last night we were on the Interstate Highway in very heavy slow traffic and the same time happened again (P1121).
This time I was able to erase the DTC code and on engine restart all was well again for maybe another 10 miles than heavy traffic again and back into limp mode (P1122).
I exited the highway and erased the DTC code (Ok on engine restart).
We stopped at one of the shorefront restraunts on the sandy beach along Long Island Sound for dinner and hopefully a break from the heavy traffic.
About and hour and half later, we were back on the highway without all the traffic that was there before and no other problems occured on the rest of the travel home.
Well that is the background and here is the results of my research:
I found the part number (0501 310 401) for the ZF5HP24 transmission speed sensors (both the input and output have the same sensor part number).
These sensor's suggested retail price is about $90 to $100 each, which can be purchased from $54 to $70 from online transmission parts vendors (these are ZF parts, no aftermarket parts are available that I could find).
The CTSC (The California Transmission Supply Company) sells them for $54.17 each - shipping $9.98.
Here is a photo of the speed sensor:
No need to remove transmission, only removal of the transmission oil pan to gain access to the input and output sensors.
Here is a diagram and parts list of these 2 ZF5HP24 speed sensors (shown as Valve Body - Duct Plate Group) from the ZF Spare Parts Catalog (I added red arrows that point to the 2 speed sensors):
Maybe someone can point out which one is the input speed sensor and also identify which one is the output speed sensor (both have the same part number). Is the output ref# 27.160 or ref# 27.500?
Also look at this TSB (309-03) on Valve Body replacing - procedure - Not in Workshop Repair Manual (included instructions on replacing these speed sensors - I highlighted the sensor info in red text):
Here is another photo of the sensor showing it needs to be cleaned (current thread 2000 XJ8 transmission rebuild - where to buy parts):
The front sensor must be the input sensor (ref# 27.160?) and the back sensor must be the output sensor (ref# 27.500?). Is this a correct assumption?