AW4 Gone weird

I have changed my TCU as I thought I had screwed it up while adding switches for controlling 2nd gear and the torque converter.

Symptoms are it will select 1st correctly even if the shifter is in D or 3rd but it will then shoft straight to 3rd or 4th (wherever the shift is) instead of 2nd.

Also the torque converter does not lock up when it should.

The 2nd gear solenoid and the Torque converter work with the switches.

I checked the codes and got a 31, 33, 35 (plus a 21, 22 which I had before).

I am completley stumped as replacing the TCU made no difference.

Have you tried returning the wiring to normal to verify that it's not your switch mod?

Yep, with everything as standard it acts as the symptoms described.

It is a 96 Sport 4.0L by the way, I can;t find any decent wiring diagrams for this year.

The switchs needs to be wired to turn the power off to the ECU when your using it in Manual.

langer1 said:

The switchs needs to be wired to turn the power off to the ECU when your using it in Manual.

Click to expand...

Why is that ?

WIth the power to the TCU killed it operates OK manually, if there is something else that I could have damaged due to an ECU link please let me know.

Thanks

langer1 said:

The switchs needs to be wired to turn the power off to the ECU when your using it in Manual.

Click to expand...

As I understand it, he's not going totally manual but rather adding a switch to supply power to the #2 solenoid to force it into 2nd with the stick in (1-2). I also gather he added a switch to lockup the t/c. I don't believe backfeeding power into the TCU can damage it. I would still recommend wiring the switch as a dual-pole to disconnect the wire coming from the TCU to prevent current from flowing back into the TCU. At the very least, use a diode.

He said he swapped the TCUs with no change (before or after returning the wiring to stock?), so I'm thinking that it's unlikely that the TCU is damaged. He also stated that it will shift into 2nd gear and the t/c lockup if he manually applies power to the solenoids with his switches. I'm thinking perhaps he's gotten the solenoid wires crossed somewhere between his switches and the TCU.

Easiest way to check what's going on is to put a meter on the solenoid outputs from the TCU while someone drives it (or maybe with the tcase in neutral in the driveway). That will prove one way or another if the TCU is acting right.

Mozzer - I pm'd you a link to grab the wiring diagram.

Thanks very much for the wiring diagram, most appreciated.

The switches do wha they are supposed to, one locks up the Torque conv the other powers up the second gear solenoid.

I am going to check the other supply feed, do you know why there are two or where the fuse is located, I've checked the one in the distribution block under the bonnet, sorry, hood.

There are two power feeds. One is switched with the ignition and one is constant power. Otherwise, the TCU will keep power to the #1 solenoid when the ignition is off. I'm not sure where the other fuse would be. On the older models it was on the wiring harness about 6 inches away from the computer.