AW4 Transmission stuck in 1st gear

Hi everyone, great forum, this is my first post...

I have a 96 XJ and the transmission is stuck in first gear so I'm trying to work out the cause of the problem. There is no check engine light and no error codes on my OBDII scanner. I've checked the fuses under the bonnet and the transmission oil level seems fine although it may be a little too full.
I've unplugged the TCU and can manually change through the gears so I assume the hydraulics/mechanical aspects of the transmission are good.



1. Could a faulty TPS be the cause? I recently replaced this sensor but drove through a lot of water yesterday. The problems only started today and now the engine seems to be running a bit rough on start up.


2. Can a faulty NSS cause the transmission to stay in first gear? I don't have any problems cranking it over in Park or Neutral and the reverse lights are OK. Would these be playing up too if the NSS was at fault?


3. Solenoids?


Any idea what to check first? I came across the article below so will probably check the voltages at the TCU against the chart on page 3 of the article (Figure 3):


http://www.transonline.com/transdigest/magazines/1997-10/Shift Pointers/index.html


Are these readings taken with the TCU connected or disconnected? Is this the best place to start fault finding? Any other suggestions?

XJSteven said:

Hi everyone, great forum, this is my first post...

I have a 96 XJ and the transmission is stuck in first gear so I'm trying to work out the cause of the problem. There is no check engine light and no error codes on my OBDII scanner. I've checked the fuses under the bonnet and the transmission oil level seems fine although it may be a little too full.
I've unplugged the TCU and can manually change through the gears so I assume the hydraulics/mechanical aspects of the transmission are good.



1. Could a faulty TPS be the cause? I recently replaced this sensor but drove through a lot of water yesterday. The problems only started today and now the engine seems to be running a bit rough on start up.


2. Can a faulty NSS cause the transmission to stay in first gear? I don't have any problems cranking it over in Park or Neutral and the reverse lights are OK. Would these be playing up too if the NSS was at fault?


3. Solenoids?


Any idea what to check first? I came across the article below so will probably check the voltages at the TCU against the chart on page 3 of the article (Figure 3):


http://www.transonline.com/transdigest/magazines/1997-10/Shift Pointers/index.html


Are these readings taken with the TCU connected or disconnected? Is this the best place to start fault finding? Any other suggestions?

Click to expand...

Crawl underneath and unplug the connector for the transmission harness. Use contact cleaner and then a little dielectric grease. Post up what you get.

I'm gonna go with the TPS. They don't like to get wet.

It was the TPS which was the first thing I swapped over! I'd only replaced it last month so I put the old one back in and the transmission is running fine again.

I can't believe how easily the TPS failed, is there anyway of waterproofing them? Why did it happen the day after I went through the mud/water? I'm glad it waited until I got home and didn't die out on the trails!

Might have to start carrying a spare in the car with me.

Also, that link I posted above for the AW4 Jeep Diagnoses page had different colored wires to mine, with a wire in one of the slots not listed on the chart and a wire missing where there should have been one. A lot of the wires matched up but some were completely different and others that I thought were right didn't return the expected reading. So it wasn't much help.

got that problem in a 1998 classic, it was a faulty NSS, took it out, cleaned and worked again

chiw00 said:

got that problem in a 1998 classic, it was a faulty NSS, took it out, cleaned and worked again

Click to expand...

With a faulty NSS was it also affecting your reverse lights and not starting in Park or Neutral as well, or can it just affect your transmission only?

it was affecting reverse lights, and the tranny stucked in first, mine started in Park with no problem