Got the pretty check engine light to come on today in my 2000 LHS. After the key dance and getting P0700 and P1684 for codes I had my friend hook up his Snap On scanner to read the TCM and got code P0740. During a road test, the torque converter locked at @55 MPH and all gears were available. Fluid is good ~2 years old and is ATF+4 and level ok. Speedo works. So I'm ruling out the speed sensors and solenoid. Trans was not in limp mode. Googling P0740 and reading DodgeIntrepid.net didn't yield much but one really good post alluded to (1)Faulty torque converter clutch solenoid valve (2) Torque converter clutch solenoid valve harness or connectors (3) Torque converter clutch solenoid valve circuit is open or shorted. One possible cause is debris in the valve body and that a flush and refill (with ATF+4) might work or that the debris will work itself out if that's the case. I'm thinking the car is telling me to start saving and that a failure is in the cards. The trans has 124K so I realize that.

Can anyone offer some additional info? Is it early enough I buy time with this? The flush is probably the cheapest trick, but if the bands and clutches are going, will I be wasting $$? Anyone install a Mopar Reman lately? Any good? Thank you in advance.

p0740

1. While driving 55 MPH on a flat road, slightly depress the brake pedal enough to kick the Torque Converter Clutch (TCC) out. The RPM should rise about 200 RPM.

2. Release the brake pedal and the RPM should slowly drop about 200 RPM.

3. If it shudders or slips, change the fluid and filter. Install ATF+4.

also add a TQ converter shudder additive..

Snap-On scanner gives the FD code.
Codes P1684 and P0456 read over the odometer by cycling the key three times. P1684 simply means the memory has been cleared sometime in the last 50 ignition cycles. P0456 Evaporative System Small Leak Detected. Visually check the evaporative system for cracked or leaking hoses. Remove the vacuum hose from the top of the vent valve. Attach a hand vacuum pump to the vent valve and apply 20” Hg. vacuum. Observe the vacuum for 10 seconds. If the vacuum holds between 15.5” Hg. and 20” Hg., The valve is OK. If the vacuum drops below 15.5” Hg., replace the LDP Vent Valve.
See TSB # 25-001-02 Rev. A.

1. Drive about 60 MPH on a smooth straight road. Check the Torque Converter Clutch (TCC) operation.

2. If it shudders or is not smooth when engaging, flush the fluid and put in only ATF+4.

3. If there is no converter lock-up, replace the torque converter.
Tech Tips:
The P0700 code means that the Transmission Control Module (TCM) has a stored code and requested the MIL be turned on. On this vehicle the TCM and PCM are in one computer but the scan tool has to go into the individual module to read codes.

Reported Fix Details Confirmed Fix
Jim Tupper
January 06, 2011 2002 Dodge Intrepid, SE 3.5L, Vin V *
Torque Converter
- a new torque converter repaired vehicle
Torque Converter
Ed Beaulieu
June 16, 2009 2002 Chrysler Concorde, Limited 3.5L *
Torque Converter
89,000 miles Torque Converter
8812PROFAST
October 17, 2011 2002 Chrysler 300M, Special 3.5L, Vin K, USA/Canada *
Automatic Transmission
Automatic Transmission Filter
Automatic Transmission Fluid
- Customer stated that the car shifted hard and made a clunking noise. She also stated that the check engine light was on. Had P0700 and P0740 stored. Verified that the torque converter was locking up using scan tool. Performed a transmission fluid flush and it DID correct the problem.
Automatic Transmission, Automatic Transmission Filter, Automatic Transmission Fluid
Rod Posner
June 26, 2009 2002 Chrysler Concorde, LXI 3.5L, Vin M, USA/Canada *
Automatic Transmission
Torque Converter
55,513 miles Automatic Transmission, Torque Converter

Thank-you . I took the car to the Dodge dealer around lunch and talked to shop foreman. He looked at the fluid and mentioned it looked weak and was high, which is odd as I hadn't added any. Also performed some tests with the DRB3. Recommended performing a transmission flush and adding some type of BG additive. The DRB3 results looked good (I'm not knowledgeable enough to define them). I rolled the dice and said go for it on the flush. Cleared the codes and I was on my way. 20 miles later the check engine light returned. Not sure on the next step. I figure I need more mileage to get the fluid and additive to work(?)

If 20 miles on the flush is insufficient, can the TCM codes be cleared using an Actron CP9180 scanner? I know the Snap On and DRB3 can clear them, but I was unable to do with the Actron.

the scanner should clear the codes, if not unhook both batt cables, touch them together for a few seconds and that will erase the codes.. also try Dr, Tranny.. its in a red tube, it may help, you can get it AZ or other part stores
http://www.lubegard.com/~/C-230/Dr.+Tranny+Instant+Shudder+Fixx

i wanna say the last time i had this code, i pulled the VB and sol pack.. and replaced them with re-man units.. but its been a while..

and as far as the BG treatment seems most dealers use it.. im not impressed with it.. I like the lube guard products for transmissions

How likely is it that it's the TC? - Did not drive the car today.