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lockup not working

T

torfinn

NAXJA Forum User
Location
Norway
I have an 89 XJ with AW4 and 4.0L. Recently I have noticed that lockup is not working. I results in higher rpms and lower mileage on highways. Where should I start looking?

regards Torfinn
 
Check fuses, but more likely the TPS (provides a signal to the TCU that affects shifting) or the lock-up disengage switch at the brake pedal. There are three switch functions, built into two switches, at the brake pedal: lock-up disengage when you hit the brakes, cruise control disengage when you hit the brakes, and obviously brake lights engage. Have you checked fluid level (first check)?
 
I had the same problem after I replaced my brake vacuum booster and master cylinder. On your brake pedal above the brake light switch. There is another switch. If the switch is not made up by the brake pedal being all the way out the torque converter will not lock up. Let us know what you find. HTH
 
i am not sure if it apply's to an 89 ,
my 96 aw4 started to jump out of lockup at highway speed ,(70 mph ~10 minutes )
and would push atf out of the dipstick tube .

got worse until it would slip into neutral and not move until shut off for
15~20 minutes .

no trans codes , fluid was new and level ok .

wound up being a bad turbine output speed sensor ,
located on drivers side under the tranfer case shifter bracket .
white two wire connector .
 
Problem solved.
Turned out to be the switch on the brake pedal. It is just pressed in holder, and can easy be pushed out of position if you are doing other things up there. I just pushed it back and used a multimeter at the tcu connector to verify the function. I am thinking I will add a LED to indicate lockup function.

Thanks for the replys.
Regards
Torfinn
 
I'm having the exact problem on my '90xj. Just noticed it today on the highway.

Checked the fuses, and pushed the switch back into it's holder (it was loose). No dice. I'm wondering if that switch is bad, because I don't have cruise control anymore as well. Coincidence?
How did you test at the TCU? Do the wires go directly to it?
I can't see up there good enough to know where those wires go..

-Nick
 
Consider this thread stolen :)
I don't want to start a new one, unless no one responds to this one ;)

I went outside to check my TPS, and adjusted it. It was way out (96%), so i put it at 83%. (4.70 supply, 3.9v signal). I then played with the trottle plate, and it moved very smoothly. I don't think my problem is the TPS.

I also wiggled the wires to the TCU. Everything else is working as it should. Only the TC doesn't go into lockup. Does it retain any sort of memory? Maybe I should disconnect the battery for a while? just an idea.

Found the wires that lead from the brake switch, and tested them with a multimeter. Tested ok, complete disconnect while brake is depressed.

Also, i recently threw a wheel weight. Just got them balanced again, but maybe i shook something loose?

I really can't think of anything else. I can't believe that the TCU would be bad, only on TC Lockup. there must be something else.

Thanks guys!
-Nick
 
http://wagoneers.com/XJ/tech/AW4-trans/AW4Wiring.jpg

This is the schematics you need to search for fault. Disconnect the plug from the tcu. You should ohm all three solenoids. They should be of similar value. Also ohm through the switch between ground and pin C10. All this with the ignition off.

You should also measure (ohm) the tps. It is a regular potensiometer. Measure between D1 and D3. It should be around 3,5kohm i think (it is not critical). Then ohm between D2 and D1 and then press the gas pedal and see if the reading changes.

The cruise control uses the same switch as the brakes, it is not the same as this one.

Regards
Torfinn
 
Okay, here goes:

All solenoids tested the same resistance.
The brake switch tested okay. Infinate resistance when pedal is depressed.

I reajusted the LV cable (it adjusted to where it was previously at)

I readjusted the TPS before. Measured the 3 pin connector, and got around 3.5k ohms - i don't remember exactly.

The only other thing in that whole diagram is the Speed Sensor. I have a little conflicting data. There is a wire in possition C3, and it is Tan/Black. I got no measurement from it.

ALSO: Now, when i test drive it, it's developed more shifting problems. 1-2 is a little delayed, but it really doesn't want to shift into 3rd. it waits until the engine is around 3100RPM before it finally shifts. Then into OD is no problem. It still never goes into Lockup.

It seems to me that if the TCU isn't getting speed data, than these problems may be in corolation with that, and that's the last thing that I haven't 'tested'.

Now, the cool thing is, i have a 96 XJ that i can compare my findings to.

Unforunately, everything appears normal in my vehicle.

PLEASE HELP!!! :explosion
-Nick
 
If your Torque Converter Lock-Up was not functioning for a while, after repairing it, I'd suggest a Fluid/Filter change is in order.

The biggest heat producer for the trans fluid is an unlocked torque converter, the heat kills the fluid and bad fluid leads to tranny failure. The heat oxidizes the fluid and destroys its lubricating, protection and friction surface engagement properties. So if your trans has been running hot, either from a malfuntion like the TC lock-up or you've been doing a lot of towing, I'd change the fluid and get fresh good fluid in the trans.
 
Thanks, but lets get the problem fixed first.

I really thought this problem was going to be the brake switch, or TPS.
Is there a relay somewhere that could have gone bad?!

-Nick
 
I think you have a speed sensor issue.
You said the brake switch was infinity when depresse, how about when not depressed it should be like around 0-2 ohms.

I dont think driving without lockup will ruin your oil. It will be just like old cars from the seventies that did not have lockup converter. Besides the tranny has an oil cooler.

Torfinn
 
Yes, only a few ohms when the brake pedal is not depressed. I'm thinking 3.4ohms.

Any idea where i can get that speed sensor or where it's at on the transmission? It's a '90 AW4, so it's got a Speedo Cable.

Thanks
-Nick
 
langer1 said:
One other thing is engine temp, lockup will not work untill engine is up to working temp, so check your temp sensors.
Click to expand...

Wouldn't I have other problems associated with this?
-Nick
 
There is no connetion between the engine computer and the trans. At least on older models. This is according to the schematics. Therefore lockup will also work on cold engine. It is nevertheless a good idea to check the temperature sensor, for improved gas mileage.

The speed sensor is just a switch like sensor, that gives pulses as the output shaft rotates. It can be tested using an ohm meter and rotating the output shaft. (put the vehicle in 2wd, and lift one of the rear wheels and rotate it.) THen the ohm meter should read around 0 and infinity repeatedly, if it does it is probably ok. I think it should give two pulses per revolution of the output shaft.

Torfinn
 
Check the resistor pack for power, some are hooked to the EGR output and don't have power until ECU is in closed loop mode. Make sure you have power to both sides of that resistor pack.
If everything is working accept lockup I doubt there is a problem with the speed sensor.
 
torfinn said:
There is no connetion between the engine computer and the trans. At least on older models. This is according to the schematics. Therefore lockup will also work on cold engine. It is nevertheless a good idea to check the temperature sensor, for improved gas mileage.

The speed sensor is just a switch like sensor, that gives pulses as the output shaft rotates. It can be tested using an ohm meter and rotating the output shaft. (put the vehicle in 2wd, and lift one of the rear wheels and rotate it.) THen the ohm meter should read around 0 and infinity repeatedly, if it does it is probably ok. I think it should give two pulses per revolution of the output shaft.

Torfinn
Click to expand...

A bit more info in case someone searches and thinks this test will work with all AW4s.

This only works on the pre-97 speed sensor. In 97, the rear sensor changed from a magnetic reed relay type switch to a hall effect sensor that puts out voltage spikes at the shaft turns (voltage depends on rpm, virtually nothing turning it by hand). It also changed to 4 pulses per rev instead of one. The sensors are also different length so you can't just swap them. I ran into this problem putting a 99 AW4 in my MJ and trying to use an 89 TCU (I did the unconventional solution and built a converter box to use the 99 sensor with the 89 TCU).

So for the later models, hookup a voltmeter to the sensor, put the xfer case in neutral, run engine with tranny in gear and check for ac voltage coming off the sensor. If you have a freq function on the meter you should see about 66 Hz @ 1000 rpm.
 
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