4L80e issues

[twisted60]

I’m getting codes 38, 85 and 86. Where to start ? I unplugged the external connectors and cleaned with electrical contact cleaner. Where next ? Issue is she’s going into limp mode. I checked battery voltage, 14.37 coming into rear battery, reset CB, repaired 2 wire that looked if’y, checked voltage going into TCM (14v)…
So ideas on what to check next ?
Thanks


Sent from my iPhone using Tapatalk

 

[Autonomy_Lost]

Have you checked the fluid? Thats all I got.

 

[NDT]

Are you working with Supplement 7 on the 4L80E?

 

[twisted60]

Are you working with Supplement 7 on the 4L80E?

Yes, that’s where I got the codes from, what I don’t see is what to check. Or maybe I just don’t understand what it’s telling me.


Sent from my iPhone using Tapatalk

 

[twisted60]

Have you checked the fluid? Thats all I got.

Yes, truck level, warmed up and ran thru gears.


Sent from my iPhone using Tapatalk

 

[NDT]

Page 122 for error 85 and 86 discusses the TISS and TOSS sensors providing inputs to the brain that the brain is not expecting, leading to brain going to limp mode. Checking these sensors is where I would start.

 

[Retiredwarhorses]

The codes mean a component is complaining…what did the book say about those codes?

 

[twisted60]

The codes mean a component is complaining…what did the book say about those codes?

Codes were 38, 85 & 86.
38 torque converter clutch
85 undefined ratio error
86 low ratio error
I’ve changed the TISS and TOSS no change.
When everything is cold transmission runs normal RPM to MPH.
After it heats up it goes into limp mode 2nd gear only. When hot it won’t move if I shift into 1st gear.
Now when I try to get codes it doesn’t flash anything, transmission light stays on steady.
Hope this helps


Sent from my iPhone using Tapatalk

 

[Mogman]

If you can no longer get codes then you might have a failing TCM, complex electronics many times fail after they get warm, can you pull codes when the TCM is cold?

 

[GuntherRommel]

Replace the relay maybe

 

[twisted60]

Was able to pull codes today (used different jumper) . New code pooped up, 87,
Did some testing on TPS, I think retired warhorse mentioned to check.
With glow plug controller disconnected I got:
0.7vdc (no pedal) - 4.49vdc (pedal to the floor) from wire 355B
5.02vdc from wire 350C Manual says 4.9vdc - 5.2vdc is a good TCM
Reconnected GPC and got:
0.68vdc @ idle from wires 355B
1.4vdc @ 3000RPM from wires 355B
4.3vdc @ idle from wire 350C
3.3vdc @ 3000 RPM from wire 350C

Is that normal for voltage to drop on sense wire 355B between GPC disconnected test and eng running test ?

Thanks

 

[Mogman]

Curious, have you tried deoxit on all of the connector pins?
With so many different codes I would start to suspect oxidized connector pins.
The troubleshooting guide outlines how to test the TPS, no other measurements should be necessary.

 

[Mogman]

When testing an analog input (IE 1-5V etc) I find it much better to use an analog meter (Simpson 260) The TPS is just a variable resistor and all variable resistors, (also called rheostats and potentiometers) can get noisy, this can lead to a failure code.
Everyone has heard a volume control on a radio/amplifier etc. get "noisy" well ECMs and TCMs do not like this.
That noise is very hard to see on a digital meter, on an analog meter you should see the voltage or resistance whichever you are reading cause a nice even swing from min to max as the throttle is moved from idle to WOT, if the needle starts to jerk around and not progress smoothly you have a defective TPS.
This of course as I said is very hard to see on a digital meter...

 

[twisted60]

Curious, have you tried deoxit on all of the connector pins?
With so many different codes I would start to suspect oxidized connector pins.
The troubleshooting guide outlines how to test the TPS, no other measurements should be necessary.

1 of the first things I tried was hitting all connectors with contact cleaner, they all looked bright and shiny.
Just got back from test run after adjusting TPS, I set it at .502vdc. It started out good but went into limp mode after warming up. I tested TPS again when I got home with everything hot, my low number stayed the same .502vdc but upper number that is supposed to be over 4.5vdc was only 3.43vdc. I’m suspecting the TPS at this point.

 

[Mogman]

Not sure where you got the "over 4.5v"
The 5V supply voltage (wire 350) should be 4.9-5.2V
Wire 359 is ground.
Wire 355 the signal wire should go from about .5-4.5V
If the pot was not noisy and just went to 3.whateverV it would not set a code, it would just affect shift points, the TCM would just think the throttle was in lass than WOT when in fact it was.
Look carefully at wire 350 with the TPS connected to make sure when it gets hot that it is still between 4.9 and 5.2V otherwise the TCM is bad.

 

[Mogman]

Was able to pull codes today (used different jumper) . New code pooped up, 87,
Did some testing on TPS, I think retired warhorse mentioned to check.
With glow plug controller disconnected I got:
0.7vdc (no pedal) - 4.49vdc (pedal to the floor) from wire 355B
5.02vdc from wire 350C Manual says 4.9vdc - 5.2vdc is a good TCM
Reconnected GPC and got:
0.68vdc @ idle from wires 355B
1.4vdc @ 3000RPM from wires 355B
4.3vdc @ idle from wire 350C
3.3vdc @ 3000 RPM from wire 350C

Is that normal for voltage to drop on sense wire 355B between GPC disconnected test and eng running test ?

Thanks

OK now I am totally confused, I just looked up error 87 and it is a high ratio error, nothing to do with the TPS
One cause of a high ratio error is a slipping transmission which would be consistent with the transmission getting warm, (this would also seem to be consistent with not pulling in 1st when hot) I would drain and pull the pan and look for"mud" or metal particles in the pan, if nothing is there change the filter, add fresh fluid and try again.

 

[twisted60]

Not sure where you got the "over 4.5v"
The 5V supply voltage (wire 350) should be 4.9-5.2V
Wire 359 is ground.
Wire 355 the signal wire should go from about .5-4.5V
If the pot was not noisy and just went to 3.whateverV it would not set a code, it would just affect shift points, the TCM would just think the throttle was in lass than WOT when in fact it was.
Look carefully at wire 350 with the TPS connected to make sure when it gets hot that it is still between 4.9 and 5.2V otherwise the TCM is bad.

Page 12 of the supplement talks about voltages and it says approximately 0.5 volts closed … signal voltage increases to greater than 4.5 volts at wide open throttle.
Thanks for the help, I have another TCM here same year as mine I can pop in tomorrow and see.


Sent from my iPhone using Tapatalk

 

[Mogman]

Page 12 of the supplement talks about voltages and it says approximately 0.5 volts closed … signal voltage increases to greater than 4.5 volts at wide open throttle.
Thanks for the help, I have another TCM here same year as mine I can pop in tomorrow and see.


Sent from my iPhone using Tapatalk

I do not understand how you are focusing on the TPS, you are not getting TPS codes but are getting high ratio codes, add that to what you said about not being able to pull in 1st when hot I would suspect a slipping transmission.
Have you changed the fluid and filter?