Solved Lockup.

What controls when lockup applies and disengages?

Are those times adjustable? If so, where can the adjustments be made?

Or is there some other way of changing the lockup timing?

The computer has it integrated into its program. It provides a ground connection for the TCC solenoid. EEC-IV isn't user adjustable. Tapping the brake pedal will disengage lock up.

Hmm, ok. So, I should look for a bad wire then, or maybe a bad computer. I am assuming that the under dash computer is the controller.

You could connect a test light to the output of the computer, and monitor the lock up of the TCC while driving. The output of the computer completes the ground connection. The three prong connector has a common 12 volt (+) connection for the TCC & 3-4 shift solenoids.

Well, I found out yesterday that the under dash computer has absolutely nothing to do with the transmission. I accidentally left it unplugged all day yesterday and drove about 50 miles with no change in anything other than an OCCASIONAL check engine light. Going to hook it back up before I even start the van today.

So, that means the transmission is controlled by some other computer. Guess I need to buy a test light, make a jumper cable, and see what happens.

Hopefully nothing wrong in the transmission, but it appears to be ok, although with my mileage on an original A4LD that is incredible. No metal and no lining in the pan, no burnt smell, and nice red fluid with about 20,000 miles since the last fluid change.

R u trying to change settings, or diagnose a problem.....if you drive at a steady speed , and tap the brake pedal, you should feel the lockup disengage and then 're-engage, ......I think the under dash computer is for abs, I don't have access to my manuals so I'm not sure...but you can't reprogram the tranny, as stated before

The engine won't start without the computer so it sounds like you unplugged another module.

jlh3rd said:

R u trying to change settings, or diagnose a problem.....if you drive at a steady speed , and tap the brake pedal, you should feel the lockup disengage and then 're-engage, ......I think the under dash computer is for abs, I don't have access to my manuals so I'm not sure...but you can't reprogram the tranny, as stated before

Click to expand...

I was originally trying to change settings, but since it can't be done, it appears that I am now trying to diagnose a problem. The problem is that at freeway speeds, under load, lockup is disengaging then immediately reengaging, sometimes only once, sometimes several times in a row. This is only happening when going uphill, never on the flat or downhill. And it happens both in OD and in Drive.

This has happened twice in the past. When it did, I changed distributor cap and rotor (which were very bad) and the problem disappeared for about 60,000 miles until the cap and rotor were bad again. This time, even after changing the bad cap and rotor (which were bad), nothing has changed.

I have checked vacuum since vacuum pressure drops under load, but there is nothing wrong there.

I have also checked for any codes that may have been set, and there are none.

Since it has been an engine issue in the past, I am assuming that it is an engine issue again, though I don't have a clue what is causing it.

I have talked to several of my customers (transmission shop owners) and some think it might be the converter going out, but with no evidence in the pan and no evidence in the fluid, that idea is suspect. And of course all think rebuilding the transmission will solve the problem. And all had the same diagnoses and solutions when I had the same problem with the same transmission in the past when in fact it was an engine problem.

I would hate to spend tons of money on the transmission only to find out the problem is not fixed. I have a good spare low mileage transmission out of a 93 Aero that I could install, but again, that is just throwing parts at a problem hoping the problem will go away.

BrooklynBay said:

The engine won't start without the computer so it sounds like you unplugged another module.

Click to expand...

What I unplugged was the module under the dash that must be removed to get the doghouse cover off. The only other module I know of is located under the hood on the passenger fender well and I believe it controls fuel delivery, spark timing, and other aspects of the engine. It may control other things, like the transmission, but I don't know what. And I swapped it out with a spare I had with no change in anything.

You unplugged the ABS module as somebody previously mentioned in this thread. The PCM is on the upper driver's side under the dashboard. The bulkhead connector is under the hood above the power brake booster area.

After talking to another customer, his suggestion, which pretty much aligns with the suggestions here, is to monitor the signals to the TCC solenoid. The difference is that he suggested that I do it manually via a toggle switch with the computer completely disconnected from the circuit to avoid computer interference.

So next time I get a three-wire A4LD core in, I will figure out which wires do what then manually isolate my problem to determine exactly where to look, transmission or computer circuit.

Be sure your plugs and wires are good. If they're bad, it will mimick your cap and rotor problem. My tranny was doing what yours was, and it was bad plug wires.....and try the brake pedal tap test, that will test the tcc...also try driving the van in a lower gear and see if the problem still occurs........

jlh3rd said:

Be sure your plugs and wires are good. If they're bad, it will mimick your cap and rotor problem. My tranny was doing what yours was, and it was bad plug wires.....and try the brake pedal tap test, that will test the tcc...also try driving the van in a lower gear and see if the problem still occurs........

Click to expand...

New plugs and wires 15,000 miles ago that replaced plugs/wires with 200,000 miles on them. How do I eliminate them as the problem?

Everyone says to do the brake pedal tap, but doesn't tell me what to expect nor what the results will tell me.

Problem persists in both OD and in Drive. Don't think lockup is applied in 2nd as van is moving too slowly.

Yep... understand your dilemma......the tap test will just let you know if the tcs is disengaging and engaging the converter lockup....it's not 100 percent test.......how bout if you pull the connector off the tcs and then go for a drive.

Okay,this is closely related to MY problem,but I won't hijack this thread....I'll start a new thread. don-ohio ^)

OK. I am now ready to attack this problem. I bought six A4LDs Friday and tore two of them apart today. Now I just need to know which solenoid is the lockup solenoid, front with red wires, or rear with blue wires.

Once I know that I will make an intermediate wire assembly with switches to insert between the transmission and the wires that connect to the transmission. After installing it I will drive for a few days manually working the solenoids to determine exactly what is happening and when.

Problem FINALLY solved!

To recap, my transmission was INTERMITTENTLY falling in and out of lockup at highway speeds, but only on INCLINES, never on declines or flat roads.

The intermittent part was driving me crazy trying to isolate the problem.

A week ago the motor started running VERY rough. Opened the hood, and sparks everywhere. The center passenger plug wire was shorting out.

Replaced the wire, now everything works like it should.

Based on examination of the wire, it looks like the intermittent part was caused by the wire moving closer to metal when on an incline and returning to its former position when on the level or on a decline. Eventually the short got so bad that it did not matter what the inclination was.

When I removed the wire the first HALF INCH behind the plug connector was BARE. I suspect that until the bare spot got long enough inclination played the major role in my problems.

Thanks for the update! I'm going to mark this thread solved.