Torque converter not locking???

[XJ/CJ]

This is kinda related to XJ and since I still own an XJ I hope you'll find it in your hearts to help. I've swapped a '95 XJ 4.0 and AW4 into my '82 CJ7. The torque converter wont lock up. I've gone through many tests (TPS, brake circuit, speed sense etc.) and changed the TCU. I've looked at the TCU on a DRBII and it had no trouble codes but it said that the brake pedal was pressed. Since the brake pedal was not pressed at the time, I cut the wire to the brake pedal leaving the circuit open, and it still thought the pedal was pressed. That's is when I changed out the TCU. I wired the lock up manually and it now works (but only when I throw the switch) So I figure that I can rule out a bad solenoid.. Has anyone else had this issue what was the fix? Is there a difference between PCMs that could cause this problem like as if the previous owner unknowingly replaced the PCM with a manual trans PCM?

Thanks
-Dave

 

[seanR]

Make sure the brake light switch is working properly and adjusted.

 

[langer1]

This is kinda related to XJ and since I still own an XJ I hope you'll find it in your hearts to help. I've swapped a '95 XJ 4.0 and AW4 into my '82 CJ7. The torque converter wont lock up. I've gone through many tests (TPS, brake circuit, speed sense etc.) and changed the TCU. I've looked at the TCU on a DRBII and it had no trouble codes but it said that the brake pedal was pressed. Since the brake pedal was not pressed at the time, I cut the wire to the brake pedal leaving the circuit open, and it still thought the pedal was pressed. That's is when I changed out the TCU. I wired the lock up manually and it now works (but only when I throw the switch) So I figure that I can rule out a bad solenoid.. Has anyone else had this issue what was the fix? Is there a difference between PCMs that could cause this problem like as if the previous owner unknowingly replaced the PCM with a manual trans PCM?

Thanks
-Dave

The brake light switch is dual circuit, have you changed the brake switch?
The AW4 switch is three wire.

 

[XJ/CJ]

The brake light switch is dual circuit, have you changed the brake switch?
The AW4 switch is three wire.

The XJ switch didn't fit (interferes with the ignition switch on the column) so I used the CJ switch and used a relay to change the signal to (-) for the TCU.

-Dave

 

[XJ/CJ]

I figured it out........ The brake switch must rest at ground to allow the torque conv to lock, and when the circuit is open it will unlock.

-Dave

 

[langer1]

I figured it out........ The brake switch must rest at ground to allow the torque conv to lock, and when the circuit is open it will unlock.

-Dave

I show an output from the ECU that is in paralell with the brake switch.
The brake input is normaly open.
The ECU output will allow converter lock up, the brake is an override during braking, all other times the ECU grounds TCU input C10 using ECU output 29.
For ECU output to work you need the ECU for automatic transmission.

 

[XJ/CJ]

Looking at the diagram from the FSM it shows the switch as normally open (thats what was throwing me off) The switch must be normally closed in order for the converter to lock and when you depress the brake pedal the switch then opens and breaks the circuit telling the TCU or cruise control (reason for parallel ecm connection) to unlock/disengage. If the brake pedal was to interupt the signal from the ECM it would have to be in series with the brake switch not parallel. Pin 29 at the ECM is actually an input to deactivate the cruise control.

-Dave