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AW4 sporadically downshifting/jumping gears

travisk

travisk

NAXJA Forum User
Location
Fullerton, CA
A few weeks ago the AW4 in my 98 XJ occasionally started rapidly shifting between 3 and 4 at highway speeds. Yesterday it started doing it between 2 and 3 as well at lower speeds.

Swapped out TPS - no change

Unplugged TCU - Works exactly as expected

What should look at next?
 
Sounds like a classic selector switch issue. Lots of writeups on this.

The selector switch is mounted on the pass side of the transmission and interprets the drivers gear selection for the computers. The contacts sometime get fowled and the tranny will shift all over the place. - Ron
 
Is it throwing any codes? I lost my OD and got P0743 on my 98 and it turned out to be a thermal failure on the TCC lockup solenoid. I replaced all 3 for $65 about a year ago and have had no problems at all between 3rd and OD.
 
WB9YZU said:
Sounds like a classic selector switch issue.
Click to expand...

Is there another term for this switch? I'm not getting a lot of hits for AW4 selector switch.

98NWCherokee said:
Is it throwing any codes?
Click to expand...

No codes

cruiser54 said:
Click on the link below and go to Tip #10.
Click to expand...

I will check out the trans plug connectors.

I plugged the TCU back in and pulled the battery power for a minute to clear out all of the electronics. It seems to be OK so far but the problem is sporadic so I'll have to drive a bit more to make sure.
 
travisk said:
A few weeks ago the AW4 in my 98 XJ occasionally started rapidly shifting between 3 and 4 at highway speeds. Yesterday it started doing it between 2 and 3 as well at lower speeds.

Swapped out TPS - no change

Unplugged TCU - Works exactly as expected

What should look at next?
Click to expand...

If only you knew someone with a DRB III that could help you diagnose the issue... :repair:
 
The transmission is working great after plugging the TCU back in and pulling the battery cable.

Unfortunately now it keeps throwing a P1698 code, which is "ECM Fault No CCD Message From TCM" or "Engine control Module (ECM) unable to communicate with Transmission Control Module (TCM)".

Dammit.
 
All of these issues were caused by a failing alternator. Sideways plugged in his DRB and he said numbers were jumping all over the place, including the transmission input speed sensor and the voltage. The TCM was also intermittantly losing connection to the ECU. Electricity is weird.

Thanks Mark and Cal for the help.
 
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