P0700 and P0715 codes

Hey guys, long time lurker on the forums here but finally come across the need for my own post. I have a 1998 XJ with the AW4 transmission. This jeep is really only used to tow my boat the half mile down the road to the ramp. I usually do this in 2high and use 4high to pull it out. Recently the vehicle has been very low on power, to the point where no matter how much gas you give it will not budge in 2hi or 4hi. You have to be in 4lo to move and even then it is down on power. So these codes just popped up as well. Any initial leads or things to check?

P0700 - Transmission control system (MIL request)
p0715 - Input/Turbine Speed Sensor Circuit

Start with checking the wiring harness.

So I have an update, I did check the wiring harness visually and it looks good. So next step I decided to replace the input speed sensor and see what happens, it did not resolve the issue but I did gain more troubleshooting information.

For the first 5 min the jeep drove fine, shifting normally. Then I came to a stop sign and when I went to take off again, it was bogging very badly. RPMs go up over 2k but not much power delivery. I moved the shifter into 1/2 gear and off she went perfectly fine. I experimented some more and figured that the transmission must be getting stuck in 3rd or 4th gear which is causing the symptoms. When in 1/2 on the shifter all the power is there.

Any ideas on what could be the root cause of this? Also, is it safe to tow a boat and a jet-ski at 10-15mph to and from my neighborhood boat ramp in 1/2 gear? This is all the jeep is really used for at the moment, so if it won't cause any damage I am fine towing around in 1/2 gear for the time being. Any input appreciated!

I've never actually seen one of the 98+ speed sensors fail. More than likely you have a failing #1 solenoid, causing you to start in 4th gear. No power to the trans computer will cause the same issue. You can test the resistance of the solenoids from the connector in the engine bay on the passenger side against the firewall. 13 +/-3 ohms is normal. I would also inspect the wiring harness down to the transmission for damage. The set of 3 solenoids runs about $70 on Amazon and can be replaced by dropping the pan on the transmission.

Changing out the solenoids is relatively easy, 1-banana afternoon job. Messy though since you have to drop the oil pan on the trans. If you do it yourself, two tips - don't bother with buying the filter as it's just a metal screen that can be flushed out with some brake cleaner. Only moderately snug on the pan screws, 7-ft-lbs. Too tight and you deform the edge of the pan and it leaks, or you strip the aluminum threads out of the transmission.

You're fine to manually shift into (1-2). Go enjoy the water.

Thanks for the info! I will take a look at this stuff when I get some free time between home projects and work. Not my main concern if it is fine to drive in 1/2. Thanks again

I had a bad speed sensor and vehicle had same symptoms. When computer sees a difference between input and output speed sensor the AW4 goes into limp mode and stays in third. Made it appear you had a loss of power. Check both sensors. Fixed mine.