4l80e pcm command requirements

[Thenameless]

Thanks to everyone who always takes a minute to help people like myself stumped. It sure gets frustrating when all the problems happen simultaneously. I need to start with one and see it through. my 4l80e won't shift to fourth unless commanded by hptuners. I cannot command any function for the lockup either. I have added the input sensor and pinned to pcm as advised, double checked. Tried 2 segment swaps with same os just to be sure. Same results. Is there something I need to do with a brake switch wire to the pcm? My harness is standalone and not much is grafted between the 98 rcsb and the harness. I have put the truck on the hoist and signaled the solenoids with hptuners and have good 1-2, 2-3, 3-4 grounds when commanded. I think the pcm is looking for something that I haven't connected. I do have logs too if that helps.

 

[NickTransmissions]

What year truck are you working with? Is the 4L80e a fresh rebuild or used?

Brake light switch signal is used by the PCM to unlock the torque converter once the driver applies the brake pedal and so the ecm needs to see/know what's happening with the brakes at all times.

 

[Thenameless]

What year truck are you working with? Is the 4L80e a fresh rebuild or used?

Brake light switch signal is used by the PCM to unlock the torque converter once the driver applies the brake pedal and so the ecm needs to see/know what's happening with the brakes at all times.

4l80e is used, suppose to have been tested and good from a 2500 van early 2000, but there is no guarantee. My truck is a 1997 c1500 rcsb. Had a 4.3 manual. Its now lm7, standalone harness, 4l80e and a 14bsf.

 

[Thenameless]

Is there a reason why I can't command tcc lockup with hp tuners? Sounds like Nothing happens, and no change of voltage or grounds on the plug

 

[BeXtreme]

I would start with ringing out all the wiring between the trans connector and ECM. What PCM are you using? Have you verified that you are not getting misfire or knock indications? Have you looked at whether the PCM is getting the brake signal? Is the standalone harness even wired correctly for that?

 

[Thenameless]

I would start with ringing out all the wiring between the trans connector and ECM. What PCM are you using? Have you verified that you are not getting misfire or knock indications? Have you looked at whether the PCM is getting the brake signal? Is the standalone harness even wired correctly

Thanks for the reply. My pcm is an 0411 I believe. I do not have the brake switch wired to the pcm, this is what I am trying to determine. Is that only to unlock the converter or would it hinder upshifts aswell? The harness is a stand alone harness. Like I said previously I can command 4th gear shifts with vcm scanner when rolling or still and it shifts fine. I cannot get any action when I prompt tcc lockup. If I test the pins there is no signaled grounds or power on any of the pins besides what was already there before hand. This is what I was able to verify. It seems pcm won't command lockup or 4th gear on its own.

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[BeXtreme]

Thanks for the reply. My pcm is an 0411 I believe. I do not have the brake switch wired to the pcm, this is what I am trying to determine. Is that only to unlock the converter or would it hinder upshifts aswell? The harness is a stand alone harness. Like I said previously I can command 4th gear shifts with vcm scanner when rolling or still and it shifts fine. I cannot get any action when I prompt tcc lockup. If I test the pins there is no signaled grounds or power on any of the pins besides what was already there before hand. This is what I was able to verify. It seems pcm won't command lockup or 4th gear on its own.

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What I'm saying is that the harness might have been built wrong. You need to disconnect the connectors at the PCM and ring them out(check for continuity) between the pins on the trans connector and the pin they are supposed to run to on the PCM. I would also check to make sure none of them are shorting to ground.

I don't know the right pins off the top of my head, but if you go here: https://www.lt1swap.com/wiringharness.htm

you can find all the info you need, including what the correct brake switch signal is and how to get it into the right spot on your PCM. If the connector on your PCM is red/blue, then you have an 0411 and it will be from a 99-2002. Green/blue means you have a P59 and it would be from a 2003-2007. Just click on the right pinout page for the year range Vortec engine you have the PCM for. They highlighted the trans pins in RED on those pages, so it's easy to find.

 

[Thenameless]

Figured I would let you fellas know what was up. Finally got the trans working fine today. It was a bit of a dick around on my behalf with the wiring. I had swapped the pins in the trans connecter to change from 60e to 80e. It didn't work the first time because I wasn't getting power to the pcm from the brake switch. I put in a temp + wire to the pin on the pcm that needs power from the brake switch on a rocker switch to see if I could get action.. and voila.. 4th gear and lockup

After a bit of poking around I found the purple wire that I needed on the clutch safety switch as my truck was manual to begin with. Wired it into pcm and all is well, confirmed with hp tuner that its functioning as it should. So problem was, wires weren't switched on the plug, and no power to pcm for tcc lockup +

Onto the next thing. And thanks again for the knowledge.