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4L80E 2nd and Rev Only

dbrannon
Unfortunately I have a gasser.
But do you know if there is similar software for 454 BBC? I’m searching for it. That would be great to find a tech 2 powered software.
What do you think of the Quad Driver fault? Or the zero Output Speed?
Thanks
 
dalejohnson2000 said:
dbrannon
Unfortunately I have a gasser.
But do you know if there is similar software for 454 BBC? I’m searching for it. That would be great to find a tech 2 powered software.
What do you think of the Quad Driver fault? Or the zero Output Speed?
Thanks
Click to expand...
You should be asking our resident transmission expert, @THEFERMANATOR those questions.
 
I will dig around online and see what software is available. I forgot your's wasn't a diesel.

as for the speed signal, it can possibly be one of the speed sensors not getting signal to the PCM, might be a good sensor but something in the harness causing the issue.
 
dbrannon79 said:
Has anyone heard from Ferm? I haven't seen him online in a good while.
Click to expand...
Some time back I sent him a message but never heard back.
I hope He is okay and that his back has gotten better.
I’ll send him another message and see if He will respond.
I think a couple of the members had his phone number. Even met him in person to get some issues resolved.
Maybe those people could be hunted down and his number obtained.
Sure miss seeing his posts.
 
Thanks for the help along the way.
I gave up on finding another scan system.
I had the multimeter test that made me suspect the PCM.
I had the TunerPro link that suggested the PCM wasn't telling the transmission to shift.
I had the TunerPro show a fault on Quad Driver 2

So I decided to change the PCM.
But did something cause it to fail?
I had check resistance to ground for all leads from the PCM. They were all in range.
Today I also load tested all the items the PCM drives. Shift solenoids, injector solenoids, etc, they were all in range.
Then I remembered that the electric radiator fan that was installed by a previous owner.
I almost always just by habit turn it off before shutting down the engine.
But if I shutoff the engine first, it would sputter to a stop and the dash buzzer would make a weird noise.
So I surmised that switching off the key switch switched off the engine and the fan.
But the fan switch was on and the fan power lead was still a closed circuit to the fuse box.
The DC fan continued to spin for a bit, generating and putting a voltage backwards into the PCM.
This kept voltage to the injectors and ignition for a short bit causing the engine to sputter down and stop.
So I installed a diode to prevent the backwards power flow.
With the PCM disconnected I tested it and it no longer flows backwards.

Installed the new PCM.
Test drove.
Shifts like a dream.

BTW, I also installed the pressure gauge. Minimum should be 37psi, it was about 70psi. Driving it was about 100psi.

That should do it for now. Thanks again.
 
dalejohnson2000 said:
Thanks for the help along the way.
I gave up on finding another scan system.
I had the multimeter test that made me suspect the PCM.
I had the TunerPro link that suggested the PCM wasn't telling the transmission to shift.
I had the TunerPro show a fault on Quad Driver 2

So I decided to change the PCM.
But did something cause it to fail?
I had check resistance to ground for all leads from the PCM. They were all in range.
Today I also load tested all the items the PCM drives. Shift solenoids, injector solenoids, etc, they were all in range.
Then I remembered that the electric radiator fan that was installed by a previous owner.
I almost always just by habit turn it off before shutting down the engine.
But if I shutoff the engine first, it would sputter to a stop and the dash buzzer would make a weird noise.
So I surmised that switching off the key switch switched off the engine and the fan.
But the fan switch was on and the fan power lead was still a closed circuit to the fuse box.
The DC fan continued to spin for a bit, generating and putting a voltage backwards into the PCM.
This kept voltage to the injectors and ignition for a short bit causing the engine to sputter down and stop.
So I installed a diode to prevent the backwards power flow.
With the PCM disconnected I tested it and it no longer flows backwards.

Installed the new PCM.
Test drove.
Shifts like a dream.

BTW, I also installed the pressure gauge. Minimum should be 37psi, it was about 70psi. Driving it was about 100psi.

That should do it for now. Thanks again.
Click to expand...
Glad you took the time to find what it was that took out the first PCM/TCM before firing the parts cannon, installing a new one, and then having it fail the first time you shut down with the aux fan on. Enjoy your correctly shifting motorhome this summer!
 
Ahh.. the source of your problem is the fan pulling from the same power that feeds the PCM. you need to install a relay on the fan. I would recommend getting a fan controller to run the fan and have it setup so the ignition supplies power to the controller. then the main power for the relay from the battery. from what your describing, a simple diode won't keep it from frying the new PCM.

Hayden fan controller is what you need. look to see if you have an extra threaded water port on the engine, if not then get the controller that has a probe you can stick in the fins of the radiator. the controller is adjustable to turn on the fans at the desired temp. I have mine set at 200 degrees, and the probe is strapped to my thermostat crossover pipe.
 
dbrannon79 said:
Would you have access to anyone near you with a GM tech 2 scanner? being that your not getting any codes logged, not sure which scanner your currently using but a quick scan with a tech 2 might reveal trans codes. of course you'd have to drive it to them and for the codes to show up again after disconnecting the battery. I've learned that on older GM vehicles the tranny codes won't clear by a aftermarket scanner, only by disconnecting the battery.

If someone has one in your area, it might help point you in the right direction. you can also see live data determining if the PCM is commanding the trans to shift comparing to how it responds. limp mode can be caused by a multitude of things including engine sensors. it might be within range for the engine to operate normally, but things like the CTS and TPS can send it into limp mode. even if the TPS is miss-adjusted but still good. I was reading on the posts where you listed the reading from the TPS. it seemed rather high for idle. iirc the voltage should be lower when your not pressing on the gas pedal, I may be wrong though.

When testing the TPS, you should see a very low voltage like 0.4~ and when slowly pressing on the pedal it should steadily increase to 4.8ish without any dropouts or fast to full 5v's. again I may be wrong about the low end readings, you'd have to look up the specs on that. you should be able to find the exact readings searching how to adjust or replace the TPS on your model
Click to expand...
Correct. Looking at the 1994 driveability emissions electrical diagnoses typical value for the TPS closed throttle should be in the range of 0.3 - 0.9v

See here: pg 371
www.mediafire.com

1994_NATP-9442_DRIVEABILITY_EMISSIONS_ELECTRICAL_DIAGNOSIS_MANUAL

MediaFire is a simple to use free service that lets you put all your photos, documents, music, and video in a single place so you can access them anywhere and share them everywhere.
www.mediafire.com

www.mediafire.com

1994_NATP-9437_1994_GM_LIGHT_DUTY_TRUCK_UNIT_REPAIR_MANUAL

MediaFire is a simple to use free service that lets you put all your photos, documents, music, and video in a single place so you can access them anywhere and share them everywhere.
www.mediafire.com
 
dalejohnson2000 said:
Thanks for the help along the way.
I gave up on finding another scan system.
I had the multimeter test that made me suspect the PCM.
I had the TunerPro link that suggested the PCM wasn't telling the transmission to shift.
I had the TunerPro show a fault on Quad Driver 2

So I decided to change the PCM.
But did something cause it to fail?
I had check resistance to ground for all leads from the PCM. They were all in range.
Today I also load tested all the items the PCM drives. Shift solenoids, injector solenoids, etc, they were all in range.
Then I remembered that the electric radiator fan that was installed by a previous owner.
I almost always just by habit turn it off before shutting down the engine.
But if I shutoff the engine first, it would sputter to a stop and the dash buzzer would make a weird noise.
So I surmised that switching off the key switch switched off the engine and the fan.
But the fan switch was on and the fan power lead was still a closed circuit to the fuse box.
The DC fan continued to spin for a bit, generating and putting a voltage backwards into the PCM.
This kept voltage to the injectors and ignition for a short bit causing the engine to sputter down and stop.
So I installed a diode to prevent the backwards power flow.
With the PCM disconnected I tested it and it no longer flows backwards.

Installed the new PCM.
Test drove.
Shifts like a dream.

BTW, I also installed the pressure gauge. Minimum should be 37psi, it was about 70psi. Driving it was about 100psi.

That should do it for now. Thanks again.
Click to expand...
Curious...are you referring to the AC condenser fan on the front of the condenser or a new fan the previous owner installed? Any pics?

I also own a GM P-30 chassis Fleetwood Southwind Storm (1994) 454 TBI w/4L80E trans. I replaced my leaking oil cooler which by the way is part of the AC condenser (1 combined unit). The lower third is the oil cooler and the upper portion is AC condenser. While I had it out I cleaned the exterior of the radiator tube fins out thoroughly. Made a huge difference in running temps 10-12F drop.

Great that you found the issue made by the previous owner. Not something I have on mine (unmolested thank god). To see the AC condenser w/oil cooler repair I did I documented it here with a lot of pics...https://www.gmt400.com/threads/condenser-oil-cooler.59140/
 
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