4l80e no 4th unless commanded, no codes

[kingtal0n]

Was the ECU originally a 4l60e and if so how did you change the wiring and segment swap for the 4l80e, for mine it was both segment and a re-wiring job

If the ecu is originally 4l80e I would double check the pinouts are what you think they are and that somebody didnt do some weird 4l60->4l80e stuff to the harness

Its weird that it worked and then doesn't suddenly. Could be a wire is crushed in the harness maybe its shorting where you can't see it so it seems like the pcm is doing things but its really just a short?
Maybe disconnect the harness from the PCM and check the wiring for obvious continuity or shorts between the wires and to ground/12 even though its disconnected

[travmac79]

I think i may have unchecked the p1810 code or changed to no error reported initially. Probably the cause of all of my confusion.

Either way. When I turn ignition on with engine off, I get 11ish volts to the a, b , and c pins on the pressure manifold switch. I got continuity from pcm harness to the trans connector as well on those pins. So the wiring seems ok. What internally could cause an 1810 code?

[kingtal0n]

https://www.ls2.com/boggs/a4/DTC%20P1810%203.8.htm

Bad pressure switch is common apparently, I have not had it happen but

https://forums.holley.com/forum/holl...480#post378480

The pressure switch reports the gear after pressure flows into the circuit. So when you are seeing trans current gear 3 I think it means that literally the 4th hydraulics never pushed the switch. So I am not sure that is part of the problem for why you didnt have 4th.

[kingtal0n]

Looking at the 3 conditions to set the code I wonder if you've got a shifter misalignment issue that is screwed the manifold switch now and keeping it out of 4th gear hydraulically.

[travmac79]

I did put a new pressure switch in from oreilly. The old one didn't have any obvious physical flaws. The original Seals and "caps" on the original pressure swtich all looked fine but I changed anyways. Pretty sure the 1810 code existed when I got the swap combo, but I can't say for sure, as I don't remember. Could I have gotten a bad new part too?

[kingtal0n]

Of course its possible. I can't count how many new parts are bad. Its such a frequent occurrence I flat out stopped buying brand new crank/cam/prndl sensors. I only use junkyard 150k miles proven sensors now. I cut the wires if I need to and solder them because the factory glues the plugs into those prndl things. I could not get the new prndl to work properly. The brand new crank sensors its like somebody returned the bad one in the box. Brand new cam sensor gray but it should be black, is it 5v or 12v gray but black?

The Pressure switch though is tough. You really should put a new one. Try buy one from sonnax. I would say check the wiring, check the shifter position, make sure the ecu is properly setup to work with that transmission. I can't tell from here if it is this is just suggestions for logical follow through. Replace the pressure switch because its really not hard or bad from the bottom. While in there check the wiring isnt pinched or something.

If the wiring is right, ecu is right, shifter is right, what else is there? Internal leaks or something with the build maybe, like a stuck valve, could probably cause hydraulic issues leads to codes and bs. One of the 4l80e I built had 4th for about 5 minutes then lost it for about 5 minutes then it came back and was fine since then. Probably some goop in there, I over-do my bearings and washers when I put them together it might have stuck a valve for a few minutes. That was weird. But stuff like that can happen on fresh builds with goop inside all over parts coming loose as it dissolves. Just stuff to think about.

[kingtal0n]

One thing to keep in mind is 4th uses the 1-2 solenoid, so if the trans has 2nd it should have 4th gear control over the same solenoid. It rules out wiring to the solenoid which leaves the ECU command and transmission internally parts and fluids. And you said it would command from the scanner so the ECU had control and the trans seemed to work. That lead to the ECU being the issue but if there is some code or problem with that pressure switch it could do all kinds of weird shifting things I guess.

[travmac79]

I Accidentally deleted my last 2 comments trying to edit. Fat fingers must have hit delete.

It shifts into all gears with the code. If I clear the 1810 code while engine is running, it goes back to 3 gears with normal line pressure. Like it has been the past 2 weeks.

Did some testing. I measured 11ish volts to all3 pins with the ignition on(engine off), so it's not a broken signal wire. I measured continuity to ground on the 3 switch signal pins while my dad shifted(engine running), to see which pins were being grounded by the pressure switch. I never got all 3 pins grounding but I got some combinations of the 3 that the service manuals don't specify as being a specific range. Some seemed to "flutter" as if the switch was going on and off very quickly. I'll keep reading and testing today for more clues before I pull the pan again

[travmac79]

So after driving this morning, the code is thrown immediately on startup(engine on). Oddly enough, not always the first key cycle or drive after clearing it... i cleared it before I cranked it. I set it to where the SES light would come on with that code so I could see it in real time. When I read the code, there is no freeze frame data to look at along with it. Is that normal?

[edcmat-l1]

So after driving this morning, the code is thrown immediately on startup(engine on). Oddly enough, not always the first key cycle or drive after clearing it... i cleared it before I cranked it. I set it to where the SES light would come on with that code so I could see it in real time. When I read the code, there is no freeze frame data to look at along with it. Is that normal?

When a code sets at key on, it's been failed by the comprehensive component monitor. There is no FF data to store. FF data is/are the running conditions when a code sets.

It is ironic that your thread title specifies NO CODES when clearly there WAS a code setting that you decided to set to NER and then decided to leave out of the information provided.

This is why I normally will flash vehicles back to stock before I start tuning, if they've been previously tuned. No telling what junk is baked into them.

[travmac79]

I didn't realize I had actually changed it until yesterday. I didn't leave that information out on purpose. Yes the title is misleading now. Oh well. My bad. Jokes on me if I don't get it figured out without rebuilding the whole thing

[travmac79]

Continuing down this path of fuckery. The code is still set and now I have only 3 gears again with normal line pressure. I didn't clear the code or anything this time either. The previous drive down the road, it had 4 gears at max line pressure.

Thinking back to the install. There was a ground on the harness going back to the transmission that I bolted to a bellhousing bolt. Could that possibly cause weird intermittent stuff like this? Should it have been grounded to the body? Would that even matter?

[Shrek]

With P01 PCMs paired with a 4L80 transmission, the OEM programming of the P1810 DTC when displayed in HP Tuners, is typically set to:

- SES Enable box (no check mark)
- Error Mode (No MIL Light)

If your conversion is based on a 2002 wiring harness and a 2002 PCM, then the above diagnostic settings would constitute a "stock" setting.

The later P59 PCMs used different diagnostic settings - which you may have inadvertently copied into your older system.

The diagnostics settings that are visible in any tuning software, must interact with quite a few diagnostic routines that run in the background - that are not visible (editable) in most tuning software.

Try the above settings.

This may get the upshift into fourth gear working.

The DTC may still be set in the background - but you would need to use a scanner to determine this - as the MIL in the cluster would not be illuminated.

[travmac79]

Couldnt a worn manual valve(the one moved by the shifter) cause line pressure to bleed into the wrong pressure switch orifices? I just pulled the pan and it seems pretty free in there. Doesn't move up and down a lot but some. Does have in and out movement but that looks like it may be normal because of how it's made.

[kingtal0n]

I think you should focus on getting the computer right 100% like Shrek says, try those settings. Compare files carefully for your computer and other transmissions.

I would be flipping the SES and MIL stuff on/off turn it upside down try to rule everything out electronically.

Yes the manual valve could cause some issue but at this point if you could command the 4th with the scanner then I'm thinking the 1-2 solenoid wasn't being commanded on by the ECU originally which led to this issue, its a software problem because 1st and second work but 4th does not and that is the same solenoid and wires. IF the scanner didnt turn on 4th then we might be looking deeper but if your scanner has control over 4th then it must be the computer right? The way you describe the issue over time is confusing because I'm not sure if your scanner ever lost the ability to command 4th or not.

[travmac79]

That's how the diagnostic codes are set in the stock tune. No mil light and no ses. It's upshifting into 4th with those settings. Just at max line pressure, etc. Because of the p1810 code.

[edcmat-l1]

If the code is setting at key on, it's not a pressure issue. It is an electrical issue. Period. Like I said previously, it is being failed by the comprehensive component monitor. It is not a performance code, it is a circuit code.

[travmac79]

I said that the code came on at startup(engine on) not key on. It's stated like that in one of the previous posts. Maybe I should have left "immediately" out of the description

[Shrek]

That's how the diagnostic codes are set in the stock tune. No mil light and no ses. It's upshifting into 4th with those settings. Just at max line pressure, etc. Because of the p1810 code.

I don't believe that HP Tuners has many of the Fault Maximum Transmission Pressure triggers available for editing - if memory serves only the MAF related (i.e. if you fail the MAF to run in Speed Density tune) ones are listed (ECM 500 - 502).

I use a different software for such tasks - the P1810 DTC has the Fault Maximum Transmission Pressure option "Enabled".

If you were able to Disable this, then at least you would be able to use the vehicle in the interim.

I agree that there is likely a contributing wiring or transmission component issue - which you should continue to pursue.

[travmac79]

In the 4l80 repair manual, it reads that an illegal combination of grounded pins at the pressure switch will cause the 1810 code, as well as set max line pressure, d4 shift pattern, immediate 4th converter lockup. All of which I am experiencing. I have power to all 3 pins for the pressure switch, at the connector with the ignition on as well. I can wiggle the harness around everywhere snd it never drops that voltage. Just more info I may have not stated clearly, or in the middle of some long response.