Still have P0741 after replacing TCC solenoid

[rydrew55]

Hi all, been a while since I've been around, (put a mustang motor in my 98 explorer, rebuilt rear end etc. with a lot of help from this site). Now I have an issue with the 5r55e (code D) transmission.

The o/d off light started flashing and it clunked as it went below 20mph while slowing down. The flashing comes and goes, and the tranny works fine when light is off. When light starts flashing, it does the clunk when I stop. Other than that, it shifts smooth and strong.

I took a chance and replaced the TCC solenoid, but the symptoms are back.
Brought it to the shop and they read the P0741. Cleared it, but it came back (intermittent).

Any ideas to trouble shoot before changing more parts or getting the tranny pulled?

Thanks
RYDREW55

 

[2000StreetRod]

P0741

P0741 Torque Converter Clutch Circuit Performance or Stuck Off

Ken, does the O/D start flashing when the torque converter should lock up? If so, then it sounds like the PCM is commanding the solenoid to energize but determines that the torque converter is not responding accordingly. The clunking may be due to the PCM going into "limp" mode because of the TCC fault. My ATSG 5R55E Service Manual states for P0741:

Description: TCC slippage detected
Condition: The PCM picked up an excessive amount of TCC slippage during normal vehicle operation.
Symptom: TCC slippage/erratic or no torque converter clutch operation. Flash TCIL.

When you replaced the TCC solenoid did you check for a blown out valve body separator plate gasket? Does the TCC slippage start to occur after driving for about 20 minutes? It takes that long for mine to warm up. If the gasket is blown then when the ATF gets warm the pressure drops because its flowing thru the gasket leak.

 

[drdoom]

I would say at the very least you will need to replace the valve body & torque converter.

 

[rydrew55]

I'll have to clear the code and try, but it did seem to wait a bit before coming back last time.

Not sure what I would have seen to indicate a blown VB seal, but everything looked real clean down there. Wouldn't you need to remove the VB to see the seal (gasket)?

My understanding (but I by no means know from experience) is that the clutch locks up at speed to help with gas mileage, and then releases when you slow down. The clunk happens when I am almost come to a stop, slowing down to around 20 mph.

 

[rydrew55]

More info after test drive

Brought it to the shop and they read the P0741. Cleared it, but it came back (intermittent). Works fine when light is off. When light flashing, it clunks as it goes below 20mph when slowing down.

Adding some more info

Took it on a test drive to see if I could determine if the TC was locking up as it is supposed to at highway speed.

1. Light was on when I left my house. Clunking when stopping as it slowed below 20mph.

2. Light went off after 4 full stops (about 1.5 miles) before I got to the highway. No clunking on stops

3. Got on highway light still off. Got up to speed. No issue for 2 miles. Held speed, hit the gas. Revs went up about 500 rpms when I hit the gas (from 2,500 to 3,000). Not sure how much it should increase revs with TC locked, but did not seem excessive.

4. Light came back on on the highway. Hit gas at speed, seemed like maybe the revs were a little more when hitting gas. Maybe 700 or 800 (2,500 to about 3,300).

5. Light stayed on till I got home. Checked fluid OK. Restarted, light still on.

6. OD off on on works fine, even when the light is flashing it will go into and out of od.

Any other thoughts? It really runs and shifts fine, both with the light flashing and with light out. Just that damn clunk when I stop.

Thanks,
RYDREW55

 

[2000StreetRod]

BPP Switch?

Is it possible the torque converter is staying locked when it shouldn't? P0741 is the wrong DTC for that but it might be worth checking the brake pedal position switch. The PCM monitors the TPS to determine when coasting and the BPP switch to determine when the vehicle is stopping. The brake pedal switch controls two separate circuits: the stop lights and the BPP signal to the PCM. An easy way to test the BPP switch is to engage cruise control on the highway and then lightly depress the brake pedal. The cruise control should disengage. If it takes more than 10 pounds of pressure on the brake pedal to disengage cruise control then the BPP switch circuit is defective. There's a brake pressure switch in the brake line to disengage cruise control as a backup safety device.

 

[drdoom]

Is it plausible that the clunk is from the ramped up pressure command of the "limp home" mode? Also, the easiest way to tell if you have lockup is to get up to cruising speed, and make note of the engine RPMs i.e. "normally at 55mph I would see around 2000rpm, but when the TCIL is flashing I'm at 2500rpm..."

 

[rickybobby]

It sounds as though the stator support bushing may have failed. IIRC that requires a new TC

 

[rydrew55]

Thanks. Is it something that can be tested to see? is it part of a new rebuilt bb or separate component that can be changed?
New TC means tranny out.

 

[drdoom]

A lot of possible causes of P0741: valve body wear, other internal leakage, bad pump stator seal, piston hub wear inside the torque converter, and thermal bypass issues to name a few.