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Torque Converter Lockup Solenoid


Well-Known Member
October 4, 2007
Reaction score
City, State
Glendale, AZ
Year, Model & Trim Level
1998 Explorer 4.0 4x4
I had a cold start/stall out situation this morning. Would idle fine in park and neutral and drove fine in reverse, but would immediately stall in drive. After it warmed up (in park) I drove to a shop. They suspected a leaking fuel injector was flooding the engine.

After about 2 hours they called and said air and fuel are good. Problem is the trans (God I hate hearing that). The torque converter is acting up. They're saying it's 80% the solenoid and 20% the converter itself. I okayed the solenoid fix ($415+) but wont know until tomorrow if it works because they're very busy.

So taking bets - is it the solenoid or converter?

If it's the converter am I looking at a full rebuild? Or can they just swap out the converter?

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I would ask to replace all shifting solenoids once they are in there. I think there are 6 of them. Something like this:


The TC can be changed, but that requires to take the transmission out.

hmmmm. isnt each solenoid $75-100? also, is replacing the 6 solenoids part of a standard tranny rebuild?

No, solenoids are easy to access with transmission on vehicle, they are part of valve body. Transmission rebuild would require to pull the transmision out.
Online are cheaper.
But, if you want to pay 400 for each solenoid when they will fail later (they have the same age all of them)... it's your right.

What I mean is, I had the trans rebuild 3 years ago. Would that typically include replacing all the solenoids?

Also, in my current situation, why would the solenoid work when the car is warm but not cold?

No O/D Flash
No metal shavings in the pan when they pulled it. Fluid looked good.

Mechanic said their computer is showing a fault with the Torque Converter Solenoid. So they replaced it.

I just got a call that replacing the solenoid did not change anything. Still stalls in drive. Same code for the solenoid fault is showing on their computer.

They are stumped and bringing it to a transmission shop who can activate the solenoid through the computer to see if it's responding.


Wiring outside the transmission? Bad PCM?
I thought they checked that before they pulled the cover off...

Mechanic now says it's a low fluid pressure condition. When the car is warm pressure is high enough to drives/shifts with no problems. When it's cold it stalls shifting Park to Drive.

So.. does the transmission have a pump or is that incorporated into the valve body? Should I install a tranny fluid pressure gauge????

could a bad MAF throw a transmission solenoid code? I know it can drastically affect shifting when it goes bad.

Mechanic now says it's a low fluid pressure condition. When the car is warm pressure is high enough to drives/shifts with no problems.
AFAIK, higher temperature makes the fluid thinner, causing the pressure to drop, not the other way around.

So an update on this, I had the TCC solenoid replaced. Mechanic said code cleared and it passed all tests.

I picked it up and it drove great... for about 4 days. Starting to shudder again. Then bam, back to square one, stalls out in the morning when cold and shifting into drive. I let it warm up and limped it to work. During lunch that same day, I get a CEL. Since I'm already out for lunch I take a side trip to autozone to get the code read - p0743 which is an electrical fault in the same solenoid they replaced.

I had to go to the airport that same day and couldn’t bring it to the shop. So it sat for 6 days. I made plans to bring it in to the shop. The 2 days after I return, I'm driving to work and the CEL turns off. Huh?

I haven’t brought it back to the shop because it's been driving fine all week. No shuddering or stalls.

Any insight? I'm thinking the solenoid could be loose or something simple like that...

Not fixed. It got worse.
Solenoid was replaced which did not do anything. The valve body was replaced, which included all six solenoids and the internal harness and that did not do anything.

P0743 CEL would cycle on intermittently, so I drove on it for a couple weeks until the intermittent problem became chronic (as a general rule, mechanics are horrible at fixing intermittent problems).

Now the CEL does not cycle, it stays on. It will stall out in all Drive gears and my truck is in the transmission shop. They replaced the valve body again under warranty that that didn’t help. They are diagnosing the electrical and wiring now hope to have an answer soon.

They think it’s the computer. I think it’s something simple like a bad wiring harness that is grounding out. Either way, from my research, I am sure this is an electrical problem. It's just really hard to find a shop that's good at electrical work and do the proper testing.

If you recently got a CEL for this, I would first examine the external wiring. Start with the connectors on the transmission and trace them up to the computer. They can melt against the exhaust manifolds. If the wires look ok, remove the pan and test or just replace the solenoid. Don’t pay a shop to do this; if you can change your own transmission filter you can replace the solenoid.

I fixed mine by dropping the pan and cleaning the contacts on the internal lead strap. The connected to all the solenoids. The 7 pin connector looked bad, so I used an emmery board to clean the flat pins. I then checked the ohms thru the PCM connector and found everything good. No more P0743 code.