2005 gto 6.0 / 4l60e

[02CCSB]

Looking for some help here... I'm a transmission guy & had this car droppped on my lap. It has had repeat 3-4 clutch pack failure. After doing some road testing and data logging, I can see that the transmission isn't being commanded to raise line pressure (pcs amperage command never drops below .8, max line pressure is achieved at 0, but realistically, I'd like to see a # in the low .1 range)

Can someone look at this cars tune and tell me if theres anything obvious?

TPS works & I'm thinking it's MAF. The reason I say that is that it never exceeded .51g/sec during the road test.

The other thing that concerns me is that this car has an aftermarket stereo in it and the factory one was a speed sensitive style.

1491114912

[joecar]

I haven't looked at your files yet, but the MAF is a major concern... unplug the MAF and see if PCS current drops.

[02CCSB]

OK shall do.

As I posted in my other thread, is there a way to map PCS amperage drop to the TPS instead of to the MAF/VE?

[joecar]

That is not an easy thing to do...

it can be done mechanically with the vacuum modulator conversion (but vacuum is not linear with throttle position).


The best way is to fix/replace the MAF and any other problems.

[joecar]

Do you have another known-good MAF to try...?

[02CCSB]

I do not have a known good one.

That was my concern with the vacuum proposition, since the cam is relatively large, it will always have low vacuum and likely shift very hard, ie - not very streetable.

[02CCSB]

If I unplug the MAF, then PCS amperage should drop to max?

[ScarabEpic22]

Vacuum/MAP shouldnt be messing with shifts, the 4speeds are done with as pattern vs TQ. If the MAF isnt operating correctly, it will max out line pressures and shifts will be brutal.

Id try applying the MAF Patch B9901 and seeing if that makes a difference, then Id try going SD (have to apply B9902). Swap MAFs if you can.


Side note, it would be good to have the Torque Model added to E40s, Ill put a request in for it.

[02CCSB]

I *could* and *would* go SD, but then I'm waaaaaaaaaaay out of my realm as a novice tuner. Dmax, I can handle, LS I have no experience or knowledge. No clue how to tune these things, my responsibility here is to get this transmission to have pressure rise.

Quite frankly, whoever tuned this car is probably as clueless as I am. The idle quality sucks for a .222' @ .050" cam. It makes power, but it's clearly not reliable.

[joecar]

If I unplug the MAF, then PCS amperage should drop to max?If the transmission fault max pressure table has the MAF DTC's enabled, then commanded pressure goes to max (PCS current drops to almost zero); otherwise if the MAF DTC's are disabled in this table, the VE table is used to calculate torque and commanded pressure (you will see PCS current drop as load increases).

[joecar]

When you unplug the MAF, then either of the following will happen:
- if the trans fault max pressure table has MAF DTC's enabled, then commanded pressure goes to max (PC current drops to zero);
- if the trans fault max pressure table has MAF DTC's disabled, then commanded pressure is calculated from torque model which is calculated from VE table (PC current drops as load increases).

so if you unplug the MAF and you see either of those then the MAF and/or the MAF table has a problem;

( if the MAF does not respond appropriately to throttle opening, then the calculated torque will be low which causes the commanded pressure to be low (PCS current will be too high )

if the MAF table looks like a rising exponential curve then look closely at the MAF it may be faulty/failed, log MAFFREQ, MAF, DYNAIR.

[joecar]

To me, the MAF tables look a little low... at 10kHz I would have expected more than 300 g/s airflow.


However, that still does not explain 0.51 g/s during the road test, I would have expected 50-150 g/s for driving around on surface streets, and 270-300 g/s for WOT.

[joecar]

Erik has a good point about the MAF Error patch B9901, apply it and see what MAF reads.

[02CCSB]

Hmmm, so then could I intentionally make it reference the VE table instead of the MAF by disabling the DTCs?

[joecar]

Arghhh... the T42 file does not have a fault max pressure table.

[02CCSB]

Ok, so I'll try that MAF patch first, then a new MAF, if neither work then I'll do the vac mod. No biggie.

[joecar]

First, apply the MAF patch, log the MAF, and see what PCS current does... let's just see where we stand with that.

[joecar]

And also, unplug the MAF, make sure a MAF DTC triggers, and see what PCS current does.

[joecar]

Hmmm, so then could I intentionally make it reference the VE table instead of the MAF by disabling the DTCs?When a MAF DTC triggers, the ECM ignores the MAF and uses VE exclusively...


i.e. the calculation chain goes something like this:

VE -> airmass + spark advance -> torque -> trans pressure

[02CCSB]

Will advise