2002 Acura MDX Code P0740

Hi 4agemister2,

Here are the diagnostic procedures.


DTC P0740/40: LOCK-UP CONTROL SYSTEM
NOTE:
DO NOT perform this DTC test until all other DTCs have been repaired first.

1. Using scan tool, retrieve A/T freeze data. Clear DTCs and road test vehicle under same conditions freeze data was recorded. If DTC returns, go to next step. If DTC does not return, problem is intermittent. Check transaxle and PCM connections.

2. Using scan tool, check for any other DTCs. If any other DTCs are present, repair those DTCs first and recheck for DTC P0740/40. If no other DTCs are present, go to next step.

3. Measure clutch pressure at each clutch pressure tap on transaxle. If all clutch pressures are within
specification, go to next step. If any clutch pressure is not within specification, repair hydraulic system as necessary.

NOTE:
Lock-up control solenoid may also be referred to as torque converter clutch solenoid valve.

4. Replace lock-up control solenoid assembly and lock-up clutch pressure control solenoid valve assembly. Turn ignition off and clear codes. Ensure engine coolant temperature is greater than 176°F (80°C). Road test vehicle at 55 MPH for more than one minute. Recheck DTCs. If DTC P0740/40 returns, inspect "O" ring on torque converter. If "O" ring is okay, replace transaxle and torque converter. If DTC P0740/40 does not return, system is okay.

© 2008 Mitchell Repair Information Co., LLC.

Thank you for your advice, i was just wondering what DTC meant and how to go about measuring the clutch pressure? Thank you very much.

DTC = Diagnostic Trouble Code. HYDRAULIC PRESSURE TESTS Pressure Test Preparation Ensure transaxle fluid level is correct. Warm engine to normal operating temperature (cooling fan will engage). Apply parking brake. Raise and support vehicle so wheels can rotate. Line Pressure Test 1. With engine off, remove pressure tap plug from line pressure tap on transaxle. See Fig. 7. Attach pressure gauge to line pressure tap. Tighten hose fitting to 13 ft. lbs. (18 N.m). 2. With gearshift lever in "P" position, start and operate engine at 2000 RPM. Note line pressure. Place gearshift lever in "N" position, and note line pressure with engine at 2000 RPM. 3. Line pressure should be within specification. See HYDRAULIC PRESSURE TEST SPECIFICATIONS table. If line pressure is not within specification, see HYDRAULIC PRESSURE TEST TROUBLE SHOOTING table. Shut engine off. 4. Remove pressure gauge set. Using NEW seal washer, install and tighten pressure tap plug to 13 ft. lbs. (18 N.m). Clutch Pressure Test NOTE: Check clutch pressure at each clutch pressure tap on transaxle. See Fig. 7. 1. With engine off, remove pressure tap plug from appropriate clutch pressure tap on transaxle. Attach pressure gauge to appropriate pressure tap. Tighten hose fitting to 13 ft. lbs. (18 N.m). 2. Start and operate engine at 2000 RPM. Note clutch pressure reading with gearshift lever in appropriate position. See HYDRAULIC PRESSURE TEST SPECIFICATIONS table. 3. Ensure clutch pressure is within specification. If clutch pressure is not within specification, see HYDRAULIC PRESSURE TEST TROUBLE SHOOTING table. Shut engine off. 4. Remove pressure gauge set. Using NEW seal washer, install and tighten pressure tap plug to 13 ft. lbs. (18 N.m).

Thank you very much for your advice. I checked and everything was within spec. I then decided to take down the trans to get it rebuilt. The third gear clutch was burnt out so now after I got it back on, the indicator lights will not come on while in any drive gear, but with a little wiggle it will come on. Also, the CEL is back on and code is still P0740, but this time it says torque converter clutch solenoid circuit open instead of malfunction now. Please, any other advice would be much appreciated, I am running out of ideas here. My next step is to change out the TCC/lock-up solenoid and see how that works.

PNP switch is either out of adjustment or faulty. When this occurs, it can cause trouble codes be triggerred. Check/readjust the switch.

If the TCC solenoid has an open circuit, it could be that the wireharness is loose or has a broken wire. It could be the solenoid was damaged while doing the rebuilt.

Did you use a different scanner to perform the scanning? Does it describe an open circuit for the same code?

I use a Genisys to scan it this time and came back with same code, but with different description. I also checked with the "orange scanner" forgot the name, and it gave same code with the malfunction description instead of the open circuit like the Genisys. I went to AutoZone to check the code out and it says that maybe the fluid might be low, so i checked it and it was a little low since I didn't fill it all the way up after the rebuild. I topped it off, swapped the tcc solenoid with the one on the side, i forgot the name of that solenoid, and it still threw the code, wish i could get my hands on a used, but good a/t pressure solenoid so i can test it out before i go buy one for 2 hundred something dollar at acura. But I think in the end, tomorrow, I am going to have to go get those two solenoids and see where i am at cause those are the only two things left that does the lock up for the transmission besides getting a new torque conv and a new transmission. Head hurts.....thank you very much KHLow for all your advice.

You're welcome.

As I suspected, different scanners might provide a different description of the problem.

Go back to my previous post regarding the TC testing and perform the solenoid resistance test to see if they are within range.

If swapping the solenoids did not change the code, you might need to check the wire connection from solenoid to the PCM.

Hi there, thank you very much for your help. I found out that if I drive it in D4 instead of D5, no CEL. Weird huh, don't know what is going on now.

You mentioned in previous post that wiggling is required at times to get the indicator light to turn on.

With latest information on the D4 not triggering the CEL, it confirms the PNP switch is either out of adjustment or bad. The D5 circuit of the gear position switch is not working correctly.