P0740, P0785, P1860 + hesitation != fun
 

I have a 2000 Blazer LT 4WD AT with 80k miles on it. I am pulling the following codes which I looked up the definitions for:

P0740 - Torque Converter Clutch Solenoid Circuit
P0785 - Shift/Timing Solenoid
P1860 - TCC PWM Solenoid Circuit

The vehicle is hesitating or stalling usually between 0-30 mph, but after it reaches 30 mph it runs pretty normally. The vehicle is more likely to hesitate/stall the first couple times you accelerate to 30, but after the first 2 to 5 accelerations it behaves pretty normally.

I have found the following extremely helpful writeups (unfortunately the third one isn't loading the pictures - perhaps it could be updated?)

https://blazerforum.com/forum/showth...ighlight=p0740
https://blazerforum.com/forum/diagnostic-trouble-codes-dtcs-49/p0785-explained-28394/
https://blazerforum.com/forum/showth...ighlight=p1860

So, to me it sounds like I have an electrical issue. Can anyone give me any guidance as to why all 3 codes would be showing up? That's a lot of solenoids to hunt down and replace and a lot of wiring to find and check out.

Another source asked if these codes showed after I had done some heavier hauling which I think he was right on because thats when the MIL came on, but I didn't have a scanner at the time (recently bought one) so I can't guarantee that's what's causing the codes. I have cleared them and will be towing in the near future to see if that's what causes the codes to appear.

I know there are a lot of posts on hesitation issues and I've tried to read up on them and do searches but if I'm posting something that's already gone over I apologize.

Thanks in advance for any help. :D

The common link here would be the pink +12V source to the transmission (cavity E on the transmission inline connector). This can also cause other problems as this source also feeds the IGN B side of the ignition switch controlling many other functions in the truck.

Thanks, I'll check into it tonight (hoping I can find the sucker). I'm a little noobish. I'll look for any worn areas. Also, any ideas on why it would usually be particular to when the vehicle just starts up (and just for the few first accelerations)?

Electrical problems are often odd. It could be that when the truck sits, the harness rests just a bit different than when you are moving or when things warm up. Could be corrosion in a plug that heat affects... There are a bunch of different scenarios.

Alright well I'm more of a noob than I was hoping for. I tried to see if I could find a path of wires heading down to the transmission from the top of the engine but I failed on that. If I were to post a picture of my engine would anyone be able to help me locate the VCM? From the schematics it looks like the inline wire runs from the VCM to the tranny. Sorry for the handholding :(

The wire will actually run from the underhood fuse box to the transmission. The underhood fuse box is on the driver side fender. The PCM (VCM) is on the passenger side fender on top of the coolant overflow reservoir.

I would actually pull the electrical connection at/near the transmission and have a look there.

That's what that thing was. I noticed it for the first time last night and I laughed because it looked like an amp. I also found it strange it was mounted on top of the coolant but I suppose it's shielded from the hot temperature more over there. Thanks for the advice I'll jack it up tonight and dig around for some wires.

Alright well I got some jack stands but the floor jack I ordered online so it will take a week or more to get here so I'll have to let this post age a bit.

But get this. Last night i towed again since clearing the codes. I pulled a P0101 which is the MAF. I actually had this code before but I thought it was only showing because to tried to troubleshoot the problem by unplugging the MAF to see if the vehicle would run noticeably better/worse. (I realize I should have mentioned that in the original post, for that I apologize).

In any case, could a faulty MAF cause the 3 above codes to set? Transversely could the 3 codes above cause a MAF code to be set erroneously? At least we know what's coming back and in what order :D

I would say that they are unrelated, especially for it to be so wide spread. A failing/dirty MAF can cause transmission issues, but not typically with the solenoids/valves. More with erratic shifting and premature band/clutch wear.

As far as testing, you need a scan tool capable of frequency readings with some back probe connectors.

if CLSTR fuse #11 in the instrument panel fuseblock is blown, that can set all those transmission codes (which powers the wire swartlkk is indicating)