Need Help. P0740

I found many threads on this and know my problem is the TCC Solenoid failure.

Noone says what solenoid is the problem? There is a regular TCC solenoid, A tcc Lock-up solenoid. one for shifting up and one for shifting down. what one do I need to replace?:banghead::banghead:

My Blazer has thrown a PO740 code & it turned out to be the valve body needed to be reprogrammed. Chevy 4L60Es have a built in valve body failure. GMs answer was a new valve body which in time did the same thing. Any good tranny shop will be very familiar with this & they have found a permanent fix, provided the torque converter isn't burned up.
Sometimes if you clear the code you may find the problem fixes itself. At least for awhile My first code came a year ago & never had another problem until a month ago when I had the valve body redone. Common condition of a PO 740 code is a hard 1-2 shift & & overdrive not working but sometimes.
For what it is worth.

hrms I am not sure about the overdrive?.I will see if it works

I found many threads on this and know my problem is the TCC Solenoid failure.

Noone says what solenoid is the problem? There is a regular TCC solenoid, A tcc Lock-up solenoid. one for shifting up and one for shifting down. what one do I need to replace?:banghead::banghead:

Well what year make and model and engine and transmission and mileage?

Has code been cleared and drove to see if it comes back?

Codes do not say replace part but do say to check it out.
Start with going threw the repair flow chart for the code.

A hint on code P0740.

Code 740 says you have a open or shorted circuit to TCC solenoid.
Circuit refers to the wiring or plugin.

Yep. P0740 is an electrical performance DTC, not a valve body concern. You know the power is going into the trans ok or you would also have DTC's P0753, P0758, P0785, and P2761. The fault is either an open solenoid (which requires a complete internal trans harness) or a fault with the control circuit from the PCM to trans or within the PCM. The solenoid resistance should be 21-33 ohms measured from pins T & E on the trans side with the connector unplugged.

I will check the pins. How do I know what pins are T,E is it coded?

It is a 1998 blazer 4dr 4x4 180,000 4.3L trans is the 4t06E i think I cant find the paper that has the info.

I have had the code cleared 2 times. It comes back the very first time I turn the key and only about 2seconds after.

After some looking around I found the answer to this question. here is a link for any future people with this problem.
http://www.hotrodders.com/forum/attachment.php?attachmentid=52719

http://www.youtube.com/watch?v=rp7lzRFpttM&feature=player_detailpage

also does anyone have a flow chart for this? I looked in my Haynes and it just tells me what the code is and to take it to a dealer. I can't find any info on the wires or how to test them

I have the pan off and have access to all the solenoids. Can you tell me what pins are T&E so I can test them before I put the pan back on? All the wires in the pan look good. I see no kinks or anything like that I unplugged every one and plugged back in tight to see if maybe it was loose.

The fluid in the pan did not look all that great. has a layer on the bottom of like metal dust. It sticks to a magnet. It is about a thick as a peice of paper. The filter in it was a Filtran Filter. Is this OEM from 1998

Where everyone go that was helping me.
here is what I did. I checked T&E reading was good. I checked all the other solonids also, all checked out. Took it for a drive after I changed the fluid and filter and cleaned all connections. It now seems to me to drive fine. No loss of power at takeoff, I got it up to 70mph and it was at 2,100 RPM. Is that good??

One thing I notice is that when I do 4X4 low. it engages at about 1,500 RPM and does it with a little jump. IS THAT NORMAL??? I never had a 4X4?

The lights that tell me if I am in 2x2 4x4high and 4x4 low don't always light up?????
I also noticed that the gas gauge started jumping and it did not do that before? does that aim at ignition switch?? I was told the fuel pump is new so I am guessing not the sending unit.

My check engine light is still on but may need to be cleared first before it may go away.

Anyone that can answer any questions please do. I am sitting not knowing what to do untill I hear what to do from someone.

Ok, Gonna take it in to get tested to find what is wrong.

I left because I told you what happened to me when 3 times I had a PO 740 code that was fixed by a tranny shop after the third light, but what would they or I know. They have only been in the tranny business for 30 years. Build race transmissions & custom billet converters, Along with a full line of custom Diesel transmissions & converters.

This is a problem where it would be much easier to have the vehicle in my bay on a lift to accurately diagnose. I can send you flowcharts if you want, but a good transmission and electrical technician may save you time and money in the long run. I don't mean that as an insult but good technicians are hard to find, and if you can find one locally take advantage of the opportunity. If you happened to fix it by moving connections around the check engine light will turn off after 3 consecutive trips without a failure reported.

yeah if you can send me your flow chart that would help alot. Ill pm my e-mail

This is a problem where it would be much easier to have the vehicle in my bay on a lift to accurately diagnose. I can send you flowcharts if you want, but a good transmission and electrical technician may save you time and money in the long run. I don't mean that as an insult but good technicians are hard to find, and if you can find one locally take advantage of the opportunity. If you happened to fix it by moving connections around the check engine light will turn off after 3 consecutive trips without a failure reported.

You are 100% correct. I read post after post on this issue, on this & other sites. I finally took it to a shop because I didn't have the equipment needed to make a positive identification of the problem. Being an old retired mechanic I knew it would be cheaper to take it to a GOOD Shop. What they came back with was a valve body issue & oil flow. Basically this is an issue with the 4L60Es & others that the factory when in warranty would just replace the VB. & the problem would many times arise again but out of warranty. The GOOD Tranny Shops figured out a permanent fix to the problem. By opening up oil flow to the converter. Which fixed the issues, which the call a reprogramming of the valve body. No where on this or other Blazer sites have I seen this mentioned.
Anyway I which you luck. I not going to continue to try & convince someone that doesn't want to hear it. BYE

Read the last post. It is going to the shop next week. The guy is busy before the 4th
I just fighured I may as well check the wires to make sure I don't have a short in one while I am sitting here waiting for him to be free

the reprogramming kit looks to me like the valve body spacer. I am guessing that you are guessing that the check balls have warn out the valve body spacer plate?

I have e-mailed you the flow chart, the schematic, and the appropriate connector end views to make measurements and do tests. Any questions about test results, just ask! P0740 sets when a continuous open or short to ground is detected in the TCC sol valve circuit or in the valve itself. A worn spacer plate or sticking valves in the valve body will not cause this code to set.

Ok, I tested c1,10 and 13. They are 28

I tested C@ 4,6,7 and they are 28

I just replaced the internal wire harness with new TCC last week and checked the TCC before I put it in. It was good.



Everything looks good as far as connections go. I had the code reset at auto store and it still came back before I even get out of Park.



Can the VCM be bad??

Update. Just put everything back together and started the blazer. NO CEL came on. Need to take for a drive to make sure it wont come back. Maybe it was a loose connection somewhere.

Well CEL back on. Never even drove it. I did notice one thing though. When the key is in the on position but not running no lights are on except the gauges. I start the car and no lights come on untill about 6 seconds later and then all the lights come on. E.G. check engine, airbag, check gauges etc. On my s-10 all the lights come on when key turned not started and then stay on for about 3 seconds after I start it and go off.

Problem solved. I connected the neg side of my volt meter to pin 10 on the blue wire harness and the pos side of the volt meter to the batt. I had 12v. I disconnected the wire harness from the tranny and still had 12v. It should be 0v. I had a short in the wire and it was grounding the wire. My tcc solenoid was always on. After attempting to find the short I gave up and just ran a new wire..