AW4 slips in and out of overdrive

[lawsoncl]

On the Renix TPS, the square 4-position connector is the output for the trans computer. I think it's a grey wire on pin B. One pin should have close to 5 volts all the time, one is ground, and the other is the sensor wire. I think its a grey wire on pin B. Measure between the sensor wire and ground. You should see the meter move smoothly between around 4.6 and 0.4 volts as you open and close the throttle all the way (key on, engine off obviously). The high/low numbers are ballpark and you'll probably be at least a few tenths different. The important thing is that it swings smoothly with out any hiccups, especially in the middle.

 

[Ecomike]

Can any one confirm if this is the torque converter unlock switch, or the cruise control unlock switch or both?

Does anyone have the wire diagram on this? I am starting to think mine may be stuck in the unlock position. Going to run some meter tests, but I could use some confirmation as to whether this is the right switch that disconnects the torque converter (AW4, 87 XJ) and if not which one does send the signal to the TCU to unlock it?

I don't think mine is locking up anymore.

It's not too hard to remove the switch and clean it. You just have to be part contortionist to get to it. :} The metal bracket that holds the switch has a screw on the right side, facing the passenger side. I think it had a 1/4" hex hex, but I'm not real sure. You'll probably have to find it by feel but it's right behind the stamped M in the bracket on mine. If you take out that screw the bracket will slide to the right and come off. That's easier than trying to unscrew the switch from the bracket and having to get it back in the same place. The switch itself can be popped apart by carefully pressing in the little tabs on the side. Here's what the switch looks like (part of the bracket is missing).

 

[MapleDitch]

Can any one confirm if this is the torque converter unlock switch, or the cruise control unlock switch or both?

Does anyone have the wire diagram on this? I am starting to think mine may be stuck in the unlock position. Going to run some meter tests, but I could use some confirmation as to whether this is the right switch that disconnects the torque converter (AW4, 87 XJ) and if not which one does send the signal to the TCU to unlock it?

I don't think mine is locking up anymore.

It is the cruise/torque converter unlock switch. Unlike the stop-light switch, this one is a normally closed switch. I believe the wiring from the switch is for the torque converter only, and the other half of the switch is the air dump for the cruise control servo.

 

[89CherokeePioneer]

If you get up to 55, keep your foot on the gas and press the brake you can watch the tach rise 150ish rpms.

Assuming its actually locking.

 

[Ecomike]

If you get up to 55, keep your foot on the gas and press the brake you can watch the tach rise 150ish rpms.

Assuming its actually locking.

I tried that today, and sure enough tapping on the brake is having no effect on rpms, up or down if I hold the gas peddle steady. I also don't feel any lock up anymore. Now all I need is a 3 foot flexible midget to help me pull that friggin part.

We now return this hijacked thread back over to the founder, LOL.:sunshine: with our thanks!

 

[Ecomike]

Who stocks these at a decent price? Thinking of buying one before I pull the old one.

I tested the C10 wire while disconnected from the TCU, and ohmed from the wire to ground. I got a variable 1.2- 2 volts with the brake off, and 12 volts with the brake peddle applied.

Not sure what to make of the 1.2-2 volts, IIRC correctly my brake light switch also reads .8 to 2 volts when it is off, and it should be reading 0 volts.

Any ideas on where the stray voltage is coming from? I am guessing a bad ground somewhere, but where???????????

It's not too hard to remove the switch and clean it. You just have to be part contortionist to get to it. :} The metal bracket that holds the switch has a screw on the right side, facing the passenger side. I think it had a 1/4" hex hex, but I'm not real sure. You'll probably have to find it by feel but it's right behind the stamped M in the bracket on mine. If you take out that screw the bracket will slide to the right and come off. That's easier than trying to unscrew the switch from the bracket and having to get it back in the same place. The switch itself can be popped apart by carefully pressing in the little tabs on the side. Here's what the switch looks like (part of the bracket is missing).

 

[MapleDitch]

That switch is quite heavy-duty inside. And it is easy to take apart and clean.

There are four tabs (2 of which are visable in the pic) that you push in with a small screwdriver, and it opens up the switch and all its insides. Careful, the giant spring inside will launch when you open it!

Its a very basic switch with only 4 components inside including the spring. Clean all the parts, then 'snap' the electrical housing back together when done, just like two wiring harness connectors would go together.



Sorry, I can't help with the voltage anomaly. That yellow feed wire to C10 also feeds a multitude of other components, like the fuel pump relay and o2 relay. Perhaps check the underside of the sockets of those relays for corrosion.

 

[Ecomike]

...

 

[Ecomike]

Well I wiggled the hell out of the wires, and the switch connection and mount plate yesterday (never found the screw head, yet, to pull it out) and today the TC started locking up finally. Now when it locks up it is running at:

45 mph ---- 1700 rpm
55 mph ---- 2100 rpm
65 mph ---- 2250 rpm

I was getting:

45 mph ........ 2000 rpm
55 mph ........ 2250 rpm
65 mph ........ 2400 rpm

The last stretch of road I had to slow down to 45 mph, which is where it locked up at 1700 rpm!!:yelclap:. So I think it was still slipping a bit at 55 and 65 mph, but at least trying to lock and partially locking at 55 and 65 mph. Will test again tonight on the 35 mile drive home.

MPGs have already gone up a little too. I know it is locking up some now as the RPMs do not change now when I vary the gas a little, but the rpms varied a good bit before.

I am wondering if that 1-2 volt back voltage is not coming from the ECU on C10. I will look at the electrical drawings again tonight to see what else might be on that wire.

 

[MapleDitch]

Here are some voltage readings I just took for reference(key on engine off - tcu still connected)

My torque converter functions properly. None of the voltages varied.

across switch: 0v pedal not pressed
across switch: 11.9v pedal pressed

C10 wire to good known B+: 12.48v pedal not pressed
C10 wire to good known B+: 1v pedal pressed

ground side of switch to firewall ground strap: 15.9 ohms

 

[Ecomike]

Return trip readings were:

45-50 mph ---- 1800 rpm
55 mph ---- 2000 rpm
60 mph ---- 2200 rpm
65 mph ---- 2300 rpm (maybe 2350)

It is hard to get much more precise that that. But definately a consistant drop in rpms, and the rpms held much more steady with slight increases and decreases in engine throttle and vehicle speed, unlike before.

 

[Ecomike]

Here are some voltage readings I just took for reference(key on engine off - tcu still connected)

My torque converter functions properly. None of the voltages varied.

across switch: 0v pedal not pressed
across switch: 11.9v pedal pressed

C10 wire to good known B+: 12.48v pedal not pressed
C10 wire to good known B+: 1v pedal pressed

ground side of switch to firewall ground strap: 15.9 ohms

Thanks, but I am not sure exactly where you took your measurements (Locations at both ends???) from your descriptions. The C10 wire goes from the upper brake switch to C10 on the TCU. You lost me with the B+ readings, but they are the opposite of the readings I got using a ground to C10 wire source with everything connected and power on, engine off.

" ground side of switch to firewall ground strap: 15.9 ohms" sounds like a bad ground on yours.

I got about 15 ohms on C14 to ground, which turned out to be the solenoid.

 

[MapleDitch]

Yeah, just ignore that data. I can see now that it will not help you.

" ground side of switch to firewall ground strap: 15.9 ohms" sounds like a bad ground on yours.

Yes, I double checked it and it is indeed a bad ground. Now I have to peel back the wiring harness to find out why!


Just post up if you need a specific value measured.

 

[lawsoncl]

I recall there was a crimped connection in the big harness against the firewall just above the valve cover. About half dozen ground wires were crimped together and wrapped in duct tape. It didn't have a crimp ring, but just looked like the wires were pressed together. I put a crimp ring and soldered it when I was there. I think one of theose black wires came out and had a ring terminal under the screw for the tranny dipstick. I'd probably just add a new ground.

 

[MapleDitch]

I recall there was a crimped connection in the big harness against the firewall just above the valve cover.

Well, it was exactly where you said it would be. Turns out I have more wiring problems than I first thought.

There is 8 black wires and 1 bare wire coming off the 2 input grounds. 6 are for the injectors, 2 are the ECM grounds(straight to pin B11 & B12), and the bare wire wraps around the knock sensor wire(I think, I forgot to look that one up).


You can see in my picture the 2 wires I separated are discolored. Those are so corroded inside there is almost no connection inside. Those 2 are the ECM grounds.

All the other grounds are fine. I had to replace those 2 corroded wires all the way to the ECM. I don't know what would have caused that.









And the Jeep runs FINE.


This did not cure my bad ground at the torque coverter switch either. That ground seems to follow a route that goes under the brake booster. I'll check that out tomorrow.


So I'll stop cluttering up this thread now!!


:wave:

 

[Ecomike]

Mapleditch,

" So I'll stop cluttering up this thread now!!"

Clutter away, your doing fine!!!

 

[MapleDitch]

Alright....

I found the right ground wire for the torque converter switch.


Coming out of the harness in the engine bay next to the air box and in front of the washer bottle, are 3 ground wires on 2 terminals that bolt to the driver's fender. The thicker gauge wire on a single terminal is the culprit. It is a thicker wire than the wire at the switch, so there must be another ground splice in the harness.

But I don't need to worry about that. My problem is my driver's side fender is a bad ground. I ran a new wire straight from the battery to all 3 grounds.



Now I have only .1 ohm at the torque converter switch to any ground!!

arty: