P1870 on 4l80e 2000 yukon xl 2500, changed harness and solenoids...

[TastelessTater]

Code p1870 is still being thrown. I had heard the abs issues I had with the ebcm might have caused it. I got the abs codes fixed but the light still stays illuminated with no codes thrown. I changed out the harness and solenoids for the transmission although this one also leaks through to the large connector that goes from inside the trans to the outside which sits on the side of the trans. Did I get a bunk harness? Should I still look there? Should I just get a new torque converter?

Note: vehicle drives fine if I clear the code and keep it in 3rd. Overdrive is when the code gets thrown.

 

[Donal]

So, P0187 can be elusive. Have you researched the code? Maybe checked for a typing error?

 

[TastelessTater]

So, P0187 can be elusive. Have you researched the code? Maybe checked for a typing error?

Sorry p1870, I've researched it for hours on end.

 

[NickTransmissions]

Sorry p1870, I've researched it for hours on end.

P1870 in a 4L80E is usually torque converter failure.

How many miles on the trans?

 

[TastelessTater]

P1870 in a 4L80E is usually torque converter failure.

How many miles on the trans?

Assuming it's the original trans then 186k. But 1-3 shift very well. Been driving it for over a year locally staying 55mph or less. Does that still sound like a torque converter issue?

 

[NickTransmissions]

Assuming it's the original trans then 186k. But 1-3 shift very well. Been driving it for over a year locally staying 55mph or less. Does that still sound like a torque converter issue?

ETA: Replace your harness - I've seen 4L80E go into limp mode due to fluid leaking through the harness connector.

Something is causing your PCM to think your TCC to slipping in 4th gear for too long after it's supposed to be "locked" (TCC applied) for two consecutive drive cycles trigging P1870 to store. Could be a myriad of things, including:

> Worn TCC regulator valve - common problem (valve body)
> Worn AFL valve - common problem (valve body)
> TCC Clutch degradation
> Apply circuit leak in overdrive (worn 4th apply piston lip seals, etc)
> worn turbine shaft sealing rings
> Worn/flattened converter clutch o-ring on the input shaft
> Worn pump stator shaft bushings, especially the rear bushing (common)
> Worn pump body bushing
> Worn TCC valves in the pump cover (back half of the pump)
> Malfunctioning PWM solenoid (or aftermarket solenoid bad out of the box) - You have replaced
> Bad Harness - You have replaced

Given the amount of miles, I wouldn't be surprised if it was multiple of the above

Looks like you've started with the easy stuff (harness and solenoids) and the code still persists so at this point, next step (before spending any more time and/or money) is to take it for a test drive w/ a scan tool to see if the PCM is issuing TCC commands as it should and then monitoring the TCC to see if it's coming on and at what RPMs and to determine if it's actually slipping.

If your scan tool confirms TCC slippage in 4th then you'll need to determine if the problem can be solved with the trans still in the vehicle or if it will have to come out to be fixed. Assuming it has to come out, I would do a complete and total overhaul and install a valve body/hydraulics improvement kit if you plan on keeping the vehicle.

For issues sourced to the valve body, you can install a shift or valve body kit. They will usually contain updated 'drop-in' valves for the TCC regulator as it is very often found to be worn in higher mileage 4L80Es. I would imagine your AFL valve is also worn and, if put on a Vac Test machine, would hold less than 15 inches.

If you want to upgrade the each of the valves a la carte (i do this, i dont buy shift kits) both Sonnax and Central Valve Bodies out of Oklahoma carry updated AFL and TCC regulator valves. Though Sonnax requires you to ream the bore to install their AFL valve. Central Valve Bodies sell drop in AFL valves for the 4L80E that do not require any machining..Neither company's TCC valves require reaming/boring to be installed - they just drop right in. I've been using Central Valve Body's AFL valves as of late in 4L60s and 4L80s with good luck so far.

For now, keep the trans out of fourth as much as possible until you can confirm the TCC is or is not in fact slipping and plan to overhaul the transmission sooner rather than later given the mileage. If you plan to take on the job yourself, let me know and ill do what I can to help you.

What did the fluid look like when you dropped the pan initially? What, if anything, was on the bottom of the pan?

 

[TastelessTater]

ETA: Replace your harness - I've seen 4L80E go into limp mode due to fluid leaking through the harness connector.

Something is causing your PCM to think your TCC to slipping in 4th gear for too long after it's supposed to be "locked" (TCC applied) for two consecutive drive cycles trigging P1870 to store. Could be a myriad of things, including:

> Worn TCC regulator valve - common problem (valve body)
> Worn AFL valve - common problem (valve body)
> TCC Clutch degradation
> Apply circuit leak in overdrive (worn 4th apply piston lip seals, etc)
> worn turbine shaft sealing rings
> Worn/flattened converter clutch o-ring on the input shaft
> Worn pump stator shaft bushings, especially the rear bushing (common)
> Worn pump body bushing
> Worn TCC valves in the pump cover (back half of the pump)
> Malfunctioning PWM solenoid (or aftermarket solenoid bad out of the box) - You have replaced
> Bad Harness - You have replaced

Given the amount of miles, I wouldn't be surprised if it was multiple of the above

Looks like you've started with the easy stuff (harness and solenoids) and the code still persists so at this point, next step (before spending any more time and/or money) is to take it for a test drive w/ a scan tool to see if the PCM is issuing TCC commands as it should and then monitoring the TCC to see if it's coming on and at what RPMs and to determine if it's actually slipping.

If your scan tool confirms TCC slippage in 4th then you'll need to determine if the problem can be solved with the trans still in the vehicle or if it will have to come out to be fixed. Assuming it has to come out, I would do a complete and total overhaul and install a valve body/hydraulics improvement kit if you plan on keeping the vehicle.

For issues sourced to the valve body, you can install a shift or valve body kit. They will usually contain updated 'drop-in' valves for the TCC regulator as it is very often found to be worn in higher mileage 4L80Es. I would imagine your AFL valve is also worn and, if put on a Vac Test machine, would hold less than 15 inches.

If you want to upgrade the each of the valves a la carte (i do this, i dont buy shift kits) both Sonnax and Central Valve Bodies out of Oklahoma carry updated AFL and TCC regulator valves. Though Sonnax requires you to ream the bore to install their AFL valve. Central Valve Bodies sell drop in AFL valves for the 4L80E that do not require any machining..Neither company's TCC valves require reaming/boring to be installed - they just drop right in. I've been using Central Valve Body's AFL valves as of late in 4L60s and 4L80s with good luck so far.

For now, keep the trans out of fourth as much as possible until you can confirm the TCC is or is not in fact slipping and plan to overhaul the transmission sooner rather than later given the mileage. If you plan to take on the job yourself, let me know and ill do what I can to help you.

What did the fluid look like when you dropped the pan initially? What, if anything, was on the bottom of the pan?

Thank you for all that info. The fluid looked good, clean, no deris, smelled fine. I have access to a snap on scanner. But I'm a timber faller/tree climber who know only random stuff about vehicles, learned out of necessity, so I don't know how read all that stuff exactly. Always caught on fast though, I'll see if I can find a video on it somewhere in the internet. Is it possible it could be the TCC valve alone? I know it was common issue on 4l60e's but didn't know it was with 4l80e.

 

[NickTransmissions]

Thank you for all that info.

You're welcome

Is it possible it could be the TCC valve alone?

Yes, it's possible

If you're up for it, drop the valve body assembly, partially disassemble it (separate the accumulator housing from the separator plate and valve body) and remove the stock tcc valve; install a Sonnax or Central Valve Bodies TCC regulator valve.

Here's the sonnax page for vac testing the valve body and pump. Note the info in each box for the TCC reg and AFL valves on the valve body page. Both of those valves are commonly worn in high mileage 4L80Es.

If you replace both, you will make that valve body much healthier all other things equal. Whether or not it fixes your P1870 issue is unknown, at least not until you try it.

If it doesn't and your scan tool confirms p1870 is in fact storing due to the converter clutch slipping or falling out of lock up, it's time to pull the transmission/TC for overhaul or replacement.

 

[TastelessTater]

You're welcome


Yes, it's possible

If you're up for it, drop the valve body assembly, partially disassemble it (separate the accumulator housing from the separator plate and valve body) and remove the stock tcc valve; install a Sonnax or Central Valve Bodies TCC regulator valve.

Here's the sonnax page for vac testing the valve body and pump. Note the info in each box for the TCC reg and AFL valves on the valve body page. Both of those valves are commonly worn in high mileage 4L80Es.

If you replace both, you will make that valve body much healthier all other things equal. Whether or not it fixes your P1870 issue is unknown, at least not until you try it.

If it doesn't and your scan tool confirms p1870 is in fact storing due to the converter clutch slipping or falling out of lock up, it's time to pull the transmission/TC for overhaul or replacement.

Alright, but if it reads that it is slipping prior to changing the new tcc valve(and afv) then it would still need to overhauled correct? So best thing to do would be to do that first? Or could the valve cause the scanner to read slipping thus meaning that i need to start there first regardless?

 

[NickTransmissions]

Alright, but if it reads that it is slipping prior to changing the new tcc valve then it would still need to overhauled correct? So best thing to do would be to do that first? Or could the valve cause the scanner to read slipping thus meaning that i need to start there first regardless?

Id confirm with a scanner that it's slipping before doing anything else. Will give you an opportunity to fully scrutinize the trans from an electronic command and control perspective.

If it its def converter clutch falling out or slipping then attempt the repair with the two valves (replace the sealing rings on the 2-3 and 3-4 accumulator pistons as well when you have the assembly on the bench) and see if that fixes it. If not, its either converter or trans which means overhaul.