The 5 Transmission p codes

Mooseman said:
Possible. I know the shift kits for these only go to 2006. Car-part.com only lists 2004 as compatible for 2004, 2002 and 2003 as compatible to each other, 2005 to 2007 as compatible, 2008 by itself with two different transmission models, and 2009 by itself.
Which kits? I got a Transgo kit for my 07.5 Silverado (same trans) and they make them for up through 2009.
 
I believe they are all physically/mechanically the same trans. Maybe different electronics/sensors. The 05 or 06 and up the trans had its own controller, in our trucks. The PCM became ECM and there was a separate TCM.
 
Sparky said:
Which kits? I got a Transgo kit for my 07.5 Silverado (same trans) and they make them for up through 2009.
It's the CTPowertain code buster kits. Quite possible that those kits are limited to some years. Some parts may be for some years while the TransGo shift kit itself works up to 2009.
 
Ah, right. As far as the shift kit part goes that is the same. Separator plates changed a bit. I asked them if they had anything for the 07 and they said yes they do have the 07-08 separator plates, just was not bundled in a kit. Told me go ahead and order the 06 kit but ask for the 07 separator plate in the notes. I have that now on my bench for install at some point.
 
So mechanic swore up and down my transmission was no good, it was slipping and had lt had lots of metal shaving in the pan. Well got a good used tranny. He installed it. I still have limp mode and those damn 5 transmission codes. He thinks it may be my PCM now. I am 1400 $ into this repair and no farther ahead then when I started. IS there a way to know if this could be a PCM issue. Or any other ideas out there. 2 months now without my blazer even after three mechanics and a transmission. So frustrating, but I am sure I can count out anything internal on the transmission. Is there a link on replacing the external harness anywhereÉ
 
If the tranny did have all that metal in the pan, it was probably a goner anyway.

Just to confirm, did you check the voltages and grounds at the connector? Look at the schematics and trace each wire to the termination points, whether it is a ground, power or at the PCM. If all checks out, then suspect the PCM. Although they are not known for failing, it does happen. If you have a pick-a-part nearby, that would your cheapest option. Just replace it and do a security relearn. Those from 2003 to 2005 would work.

Hell, I have a spare one from a 2003 I can't use because mine is a 2002 I could sell cheap.
 
Hi Mooseman,

I did check the pink power wire at the connector on the end of the harness itself and power was good. I tried to check ohms with a DMM. But not sure if I did that correctly or not. I did not get ohm readings anywhere using the guide earlier in these posts. I tried key on and off.

What schematics would I be looking for to trace wires?

As usual any and all help will be appreciated.

P.S. I have a spare PCM unfortunately it is also from a 2002.

Thanks Mooseman.
 
There are schematics for the tranny wiring in the manuals. Just check that there is no open from the tranny connector to the other end. Except for the pink power wire, all the others go to the PCM. The tranny wiring schematic is on page 85 of the 2004 wiring schematics.
 
Ok I found another proven good PCM for cheap, it is also from a 2004. The numbers on the top with the letter to the far right side are the same just the letter are different and the bottom numbers are not all the same. I do not think that matters.

For the relearn. I am thinking it is this one I am trying site.

Turn key on for 11 minutes, make sure security light is off, then turn ignition off for 30 seconds. do it 3 times then key on 30 seconds start car.
I also read I need the VIN put on the PCM for it to work and also a case relearn. Then have read you do not ?

Someone here has to be able to help me with these questions.

Thanks
 
Close. It's turn key to start, leave it in the Run position for 10+ minutes until security light goes off, turn key to off, repeat 2 more times. Fourth time it should start.

Just a warming, you will likely get a CEL and code for crankshaft angle error because it will need a CASE relearn. You can run it like this for as long as you need to, no damage or ill effects.

This process does learn the VIN to the PCM. Nothing else is required.
 
Thanks again Mooseman, relearn complete no problem. Did not fix the tranny though. Only $25 out on that one. Guess it is back to the harness.

Thanks again
 
Well, at least it rules it out.
 
I seen the video on this subject from GMTnation, I cannot find anything on it here to help me I am new to the site.

I have the five P0740 p0753 p0758 p0785 p1860.

I tested fuse 47 it has power both sides.

I swapped an ignition switch from my 02 envoy that I had smashed up. Reset codes and still got no power from vehicle.

I short test drive around the block and all 5 codes where back.

In the video it said to come here for the best help.

That's exactly what I am looking for. You help.

If there is a topic open on here already, please direct me to it. Vehicle is an 04 trailblazer LS 4x4.

Thank You all.

Don
I have same model Trailblazer, going through same song and dance. Seen same video,dude is awesome,been scratching holes in my head trying to figure out and stumbled on video. Any guidance would be beyond appreciated.
 
View attachment 67783

View attachment 67784

So yeah fuse 47 is the key on power feed to the trans solenoids. The pcm grounds the solenoids as needed.

If you got power on both sides of 47 with the key on, next thing I do is to go to the connector at the transmission. It is #10 in the second pic. It is hard to get to. With the key on, the pink wire in that connector should have good voltage. It might help to wiggle the harness 6-8" back from the connector and see if your voltage fluctuates.

In the first diagram you can see (if diagrams are your thing) that the circuit runs from the rear fuse box, up through the firewall, to the front fuse box, and back to the transmission (makes perfect sense). If no power is found at the pink wire and the wiggle test got no results, next would be the wiring at the front fuse box. But let's see the results of the trans connector first.
Bro,your a godsend. Was totally in the dark before seeing your video. Replaced solenoids,etc...thank you!!! At least got a starting point on the right path.
 
For anyone getting these codes, verify power is getting to ignition switch. I tilted the steering wheel while working which loosened the ignition connection. You may also notice low power in 1st gear like transmission is slipping and eventually a no crank no start condition. Then the power windows would not work but other accessories would. After ignition connection under the steering column was reseated and codes cleared vehicle worked as expected.
 
For anyone getting these codes, verify power is getting to ignition switch. I tilted the steering wheel while working which loosened the ignition connection. You may also notice low power in 1st gear like transmission is slipping and eventually a no crank no start condition. Then the power windows would not work but other accessories would. After ignition connection under the steering column was reseated and codes cleared vehicle worked as expected.
Having the same issues with these codes, but my car key will also not come out of ignition cylinder so have a feeling it might be related to that. How did you reseat the ignition connection? Unplug and plug back in? I imagine you had to take off the steering column cover? Thanks in advance.
 
Having the same issues with these codes, but my car key will also not come out of ignition cylinder so have a feeling it might be related to that. How did you reseat the ignition connection? Unplug and plug back in? I imagine you had to take off the steering column cover? Thanks in advance.
My key was stuck as well. This guy shows the easy way to change the ignition switch so it shows the connector.


To reseat, pull the connector out and put it back in and make sure it's connected, snapped and secured into the switch. If that's not the problem then maybe your ignition switch is junk. I replaced mine for like $15.
Dorman 924-715 Ignition Switch... https://www.amazon.com/dp/B00GJ1JC08/?tag=gmtnation-20
It freaked me out but's not a hard project. Hope this helps.

Fyi, the owner before me stripped out the negative battery terminal. Had to replace the battery at the same time. If positive and negative terminals are removed which resets system, you'll likely need to do a HVAC reset. That is, my vents air was blowing different and ac didn't work.

 
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My key was stuck as well. This guy shows the easy way to change the ignition switch so it shows the connector.


To reseat, pull the connector out and put it back in and make sure it's connected, snapped and secured into the switch. If that's not the problem then maybe your ignition switch is junk. I replaced mine for like $15.
Dorman 924-715 Ignition Switch... https://www.amazon.com/dp/B00GJ1JC08/?tag=gmtnation-20
It freaked me out but's not a hard project. Hope this helps.

Fyi, the owner before me stripped out the negative battery terminal. Had to replace the battery at the same time. If positive and negative terminals are removed which resets system, you'll likely need to do a HVAC reset. That is, my vents air was blowing different and ac didn't work.

Much appreciated, will definitely give it a try. HVAC info will also come in handy as the AC (or HVAC?) actuator that is in the back of the truck (right rear panel) has begun clicking loudly intermittently.My guess is that it's also related.
 
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Much appreciated, will definitely give it a try. HVAC info will also come in handy as the AC (or HVAC?) actuator that is in the back of the truck (right rear panel) has begun clicking loudly intermittently.My guess is that it's also related.
It's a small world. Just so happens, my house mate has an '04 TB with the rear passenger actuator that clicks. There are 2 actuators back there. You likely need to replace one but people may replace both "while your in there". Here's the actuator. If you replace both, then buy 2. We're just buying 1 of them, lol.

ACDelco GM Original Equipment 15-72811 Temperature Mode Valve Actuator Assembly , Black https://www.amazon.com/dp/B0016IDE12/?tag=gmtnation-20

This one looks good.
 
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Bro,you’re a godsend. Was totally in the dark before seeing your video. Replaced solenoids,etc...thank you!!! At least got a starting point on the right path.
Thank you for all your great info, I am now down to checking power to the pink wire. What exactly is pic #2 showing? Thanks in advance. This limp mode bs is like playing wack a mole (with apologies to the mole)!
 
What exactly is pic #2 showing?
You mean the pics in post #2? That's a diagram of the under hood wiring harness. It was to show where the connector for the tranny is (#10).
 
Thank You for the info.

You are not kidding. I crawled around under my Trailblazer for about 30 minutes. I could not find the connector. I thought I read it was on passenger side of the transmission. I only se some wires going down the driver side. All I could see was one rectangular looking connector. I am looking for the round one though correct?

I just had my blazer up on standard ramps in the front. Maybe I need to get it up hire.

Thanks again,

Don
Thanks again,

Both off you great information, and I just purchased a new digital multimeter.
I’m proudp pc is probably part to my problem with pppppp
 
Thank you for all your great info, I am now down to checking power to the pink wire. What exactly is pic #2 showing? Thanks in advance. This limp mode bs is like playing wack a mole (with apologies to the mole)!
I’m sure 👍 but PPPpp
 

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