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Multiple Trans related Codes- P0740, P0753, P0758, P0785, P1860

  #1  
Old 08-10-2011, 12:27 PM
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Default Multiple Trans related Codes- P0740, P0753, P0758, P0785, P1860

1997 4x4 Blazer, 4.3L engine. The vehicle will intermittently start out in 2nd gear, or maybe it is 3rd gear, I'm not exactly sure. The codes are listed in the thread title.

I have been doing some searching on this board, and have gleened some useful information. Such as in this thread: https://blazerforum.com/forum/2nd-ge...0-p0306-23980/

My vehicle does not have a CLSTR fuse in the #11 slot though. Mine has a TRANS fuse in the #24 slot, so I amm assuming that it is that fuse which supplies power to the TCC and shift solenoid circuits. Please correct me if I am wrong about that.

Anyway, the fuse itself is good. I wanted to see if the power to the fuse stops when my shifting problem starts, so I rigged up a simple light that was powered by the fuse terminal. That way I coulad watch for the light to go out when I started getting no downshift on the trans. I drove the car and the trans acted up like normal, but the light stayed lit the entire time, indicating to me that the circuit has power to that point.

I was really hoping to be able to pop a new ignition switch in to solve my problem, but I wanted to do a bit of diagnosis to make sure it was the problem. Since my little test light set-up remained lit the entire time I was driving, I am assuming that my ignition switch is good, and that my problem lies elsewhere. I have not had the trans pan off recently, or done anything else to the car that would casue a disturbance to the trans wire loom.

I am hoping that someone here will help me out by pointing me in the right direction to continue my diagnosis. I do not have a wiring diagram, so I can't trace wires that way. Would anyone be willing to take a poor noob by the hand and help him solve this problem? I promise to report back when the problem has been solved, in order to further the knowledge database of this fine site. There is nothing worse than finding a thread with the exact same problem that you are having, olny to find out that the resolution was never posted.

Thanks in advance for any help you can give me.
 
  #2  
Old 08-10-2011, 01:48 PM
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I would pull the connector on the passenger side of the transmission & test for +12V to pin E (pink wire). The schematic shows power to the TRANS fuse (15A #24) in key positions OFF, RUN, & START so there should be power to this wire in all of those positions (seems odd that it would have power in the OFF position to me though). If you have power to the connector, I would then check inside the trans for power to each of the solenoids. It'll be a red wire inside the transmission pan.
 
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Old 08-10-2011, 02:04 PM
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Scratch everything I said earlier about diagnosing this problem.

After mucking about under the blazer, I decided to take another drive. I still had my light hooked to the fuse. For most of the drive, the light stayed lit up and the car shifted up and down normally. The check engine light was off, as I had previously cleared all of the codes.

After I had ran a few errands, I was driving along and all the sudden my little light went off. At the same time, the check engine light turned on. The next time I stopped, the car did not downshift and I had to start out in third gear.

I decided that I would try to replace the ignition switch, so that is what I am doing now.

I posted earlier that the light did not go off when the car started showing the symptoms earlier. I guess I was wrong. Diagnostics never was my strong suit, especially on an intermittent problem. I'll post back later to tell whether the new ignition switch fixed the problem.

Later- The ignition switch is in. I took the car for a drive and it did not display the trans symptoms like before, however this problem has been intermittent, so time will tell I guess.

Thanks for the help.
 

Last edited by zlathim; 08-10-2011 at 07:27 PM. Reason: Added update
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Old 08-10-2011, 08:15 PM
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This should help:
 
Attached Thumbnails Multiple Trans related Codes- P0740, P0753, P0758, P0785, P1860-4l60e_trans_pinout-engine-side.gif  
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Old 08-15-2011, 08:21 PM
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Well, it's been several days and the problem has not resurfaced. Apparently the new ignition switch fixed it. Thanks for the help.

Zane
 
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Old 01-17-2012, 05:23 PM
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Hello guys I'm having this same problem I have trouble codes P0740, P0785, P1860, P0753 they came in this order, I haven't had a chance to look at anything yet seeing how this happend just as I was leaving for work as I started my Blazer. So I wrote the codes down then when I was pulling out of the parkade I had to floor it just to get up the incline, so I parked it and shut it off and I couldn't take the key out, it would shut off and turn back a bit but not to the off position, so I deleted the codes and the SES light when off and the key worked like normal.

I just need an idea of were to start I've replaced my ignition switch in March do to the fact that my Blazer was broken into and they forced the ignition and fried the switch and my transmission was rebuilt in 2005 when I bought it because the reverse was gone and I've only put 30,000 Klm on it since then, so I have no idea what could be the problem, could this be a cold related problem? I live in Edmonton and right now it's -29C and bin that way starting 3 days ago but before that it was like -3 or warmer

Any help is greatly appreciated Thank You
 

Last edited by Hammond1524; 01-17-2012 at 05:45 PM.
  #7  
Old 01-18-2012, 05:17 PM
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Hello again guys haven't had any issues since I cleared the codes yesturday other then on my way to work today the SES light came on again but went out a few minutes later, checked for codes in memory when I got to work and no codes everything was all green

I will keep everyone updated if this problem comes up again

Thanks again everyone
 
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Old 02-12-2012, 04:33 PM
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deleted.
 

Last edited by eak435s; 02-21-2012 at 10:15 PM.
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Old 12-26-2013, 03:00 AM
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Default PO740 p0785 P1860

I have been painstakingly trying to help my daughter with her 1998 S10 Blazer. I recently replaced the multifunction switch because the brake lights weren't working. The MF switch fixed that problem but shortly afterward she started getting these odd transmission codes P0740, P0785 P1860 which indicate a malfunction in the torque converter solenoid circuitry. As far as I know the car is still running fine but still getting these codes shortly after I clear them. The tranny fluid looks great and it seems to be shifting fine. Her car does have a remote start and I have read some threads about this causing problems. I am just at a loss and I really don't think it's a tranny problem but an electrical or voltage issue. Some of the threads dance around this, but they are really taking me nowhere. Key stuck in the ignition switch airbag light coming on but I don't have any of these problems. Does anybody have any solid advice about where to start, and could it be possible that the new MF switch is causing the problem? Thanks in advance for any help.
 
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Old 01-01-2014, 05:30 PM
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Default Remote starter triggers codes

I found out today that my daughters 98 blazer only throws on the SES when it is started with the remote starter. I cleared the codes tried the remote start and the codes were back a minute or so after it started idling. Cleared the codes again and started it with the key and no codes drove it about 25 miles no codes. Don't know much about how the remote starters work, and had this one installed a few years ago, and it was fine until I changed the multifunction switch. She was trying to get it smogged and they won't pass it when there are codes present. I believe I will drive it down tomorrow after starting with the key and it should be fine. Any info on this little issue would be appreciated.
 

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