A4LD Intermittent TCC Lockup

[Propane]

Parts replacedCM,TCC Solenoid,VSS,have completely serviced transmission,modulator ok,seems to be electrical in nature,have power to solenoid's,Drive the truck 6 to 12 miles works fine then when you start out again no lockup.Ended up backprobing harness at fenderwell at TCC wire and gounded it can hear solonoid's click - KOEO. Left wire grounded for now to prevent trans damage,works fine except for a little quicker 3-4 shift but lockup does occur.
Could this be simple as a faulty TPS sensor?!
Background:201000 Miles very good condition everything works.
This last trans service had about 10,000 Mi on it.Never anything unusual inside pan found only black/grey residue both times I serviced.
This is in a 1994 Ranger SC 4x4.

 

[BrooklynBay]

Check the solenoid, and the internal wiring harness with an ohm meter. It could have a bad connection. Wiggle the prongs coming out of the solenoid, and the wiring of the connector.

 

[Propane]

A4LD TCC Continued-

Actually have checked harness and connections all ok & nothing is really jumping out at me.Backprobed connector on PCM side at ground & TCC wire,only works consistantly when I ground TCC wire,this is why I thought PCM might not be switching ground.This thing is really starting to kick my rear! The reason I was thinking TPS was maybe it's getting out of wack when it gets some heat to it.

 

[MrShorty]

The TPS is a simple potentiometer. It wouldn't take much to put a voltmeter on the signal wire and see if you can see anything weird that coincides with the TCC locking/unlocking.

However, the first thing I would probably do would be to put a voltmeter on the TCC solenoid circuit (I would probably set it up so you're measuring the voltage drop across the solenoid). Then see what the computer is doing and see if it coincides with the TCC locking/unlocking.

 

[BrooklynBay]

Check the brake switch. It will cause the TCC to unlock if the brakes are applied.

 

[Propane]

A4LD More...

Thanks for the replies so far,checked the brake switch,works ok.
When I backprobed the connector w/paperclips & connected wire to each-black w/white stripe -ground & purple w/yellow stripe TCC & ran inside cab & hooked a test light between the leads the light never went out while driving,of course when I took the test light out & touched the leads together lockup occured.
Have replaced TCC solenoid w/new,checked with ohm meter both old & new.
New one had lower resistance & within spec,old one had higher resistance and
within spec,however click test failed on old solenoid.Have checked harness's also,the replacement PCM came from a wreck & all numbers matched.TPS voltage was smooth through throttle travel but has been replaced sometime w/aftermarket part starting & ending voltage was not right on by the book.
I will be doing further checks this week,watching Bowl games today.
Anything anybody can think of is appreciated.

 

[BrooklynBay]

Do you have LED taillight bulbs? This is a problem on the Fords. Check # 1 in my list of useful threads for more information: http://www.explorerforum.com/forums/showthread.php?t=157011

 

[Propane]

A4ld...

No L.E.D.'s,but there is a Hoppy trailer connector,but it was installed long before this started,I spent about a hour last night reading your list very informative.

 

[MrShorty]

Thanks for the replies so far,checked the brake switch,works ok.
When I backprobed the connector w/paperclips & connected wire to each-black w/white stripe -ground & purple w/yellow stripe TCC & ran inside cab & hooked a test light between the leads the light never went out while driving,of course when I took the test light out & touched the leads together lockup occured.

Sounds like you hooked it up to measure voltage drop across the PCM rather than the solenoid. I haven't ever used a test light for this, but I have uses a voltmeter. It sounds to me like, for this test anyway, the PCM never chose to command lockup. When you took out the test light and touched the leads, you provided your own path to ground, bypassing the PCM, so it locked up.

Which connector(s) did you backprobe? If you haven't already, I might repeat this test but move the backprobes to the PCM's 60 pin connector to see if there are any loose connections between your test points and the PCM.

At this point it appears that the PCM isn't choosing to command lockup. the next question I might explore is can the PCM command lockup. This is easy with the same test light setup and using the output state EEC-IV test (see my notes on pulling EEC-IV codes in the EEC-IV forum). If the circuit behaves normally (you can see the test light/voltmeter change states), that would suggest that there is a problem somewhere in the EEC-IV system that is preventing the PCM from choosing to command lockup. If it doesn't check out, that begins to suggest that there's a fault in the TCC solenoid circuit (possibly internal to the PCM) that prevents the computer from commanding lockup.

 

[TeckNine4]

"MrShorty" do you think I can take a PCM from a 95' and use it for a 95' Trans.>Inside of a 94'?

 

[MrShorty]

"MrShorty" do you think I can take a PCM from a 95' and use it for a 95' Trans.>Inside of a 94'?

can it be done? I believe most anything can be done with enough time, money, ingenuity, and other resources.

can you do this swap? I don't know, because I don't know what resources you have access to. Right now, I couldn't do it, because I haven't researched it enough, which is why I posed this question in dewgod's other thread.

I do know that there are a few small differences between the 1st gen and 2nd gen 4.0 OHV blocks. I don't believe they are enough to invalidate the '95 algorithms, but I can't say that for certain.

One of the first steps in this question would be to get a good wiring diagram for the engine management systems for a '94 and a '95 and identify what's similar and what's different. That would give an idea of how much work would be required in terms of wiring harnesses.

Someone else here may have ready access to information for this swap. If you decide to pursue, they may be able to help you. And, of course, let everyone know what you figure out.

 

[Propane]

A4LD even more...

Checked all grounds again,removed trans. harness & checked all wires -OK,checked all other harness's w/related circuts-OK,Drove the truck tonight,shifted & locked up flawlessly first 10 miles until slowing for a turn then no more lockup.I wonder now if donor PCM may have same issue as original?At least I am begining to think this is a PCM issue.
All related sensors check out OK.How can I put the PCM in output state? Could'nt find in forum's.
All pins are good in connectors & connections are clean & tight.
Thanks

 

[Propane]

A4LD Lockup

Thanks for the help MrShorty & Brooklyn Bay,I found Your Post For pulling EEC-IV codes,I have had a scanner for years but did'nt know how to put the PCM into output state test mode,I had never read about this in any manuals that I have.I'll be doing this tomorrow,and do have a reman PCM standing by.
I've been repairing Medium & Heavy Trucks & Pickups(mainly Fords)for 30 years.
Never had to much faith in these forums untill now.

 

[wood1]

The engine coolant sensor needs to show a certain temp before the EEC will allow the TCC lock-up.

Also I'm almost sure I read that a weak alternator can cause TCC lock-up issues, anyone remember reading that somewhere?

I would also check the grounds to the EEC.

Good luck.

 

[wood1]

Ha, found it.

Check the output voltage of the alternator and the harnesses where suggested in this link.

http://www.explorerforum.com/Singleton/web/pages/od.html

 

[Propane]

A4LD Intermittent TCC lockup solved!!

Long time no post sorry guys,the cause of this was a dirty MAF sensor.The reason I did'nt check this was because it had been replaced w/reman about 5000 miles prior and the Ranger ran perfect.Took about 4 months to figure out.

 

[BrooklynBay]

Thanks for the update!