Forcing VVT to Operate (GM LY7, LLT) under any situation.

[carperson]

Ok,

First time poster. I have a unique one, probably for the advanced tuners here / engineers. I am looking to disable the ECUs hard coded VVT disable functionality on codes P0008, P0009, P00016-19. -and no, not to try to limp bad chains, this has new chains, its for an engineering project, too long to get into here.

(2009 LY7, Car application)

When using a stock tune:

Using a Tech-II I can view the VVT/CMP live data, and control each phaser via the special outputs menu, working fine. (Once codes set, this command in the T2 is disabled, important for later). However because the engine currently meets the parameters for setting P0016-19 as soon as the codes set, VVT is disabled and commanded and actual phaser states go to "0". In this engine that severely degrades performance.


Now here is the interesting part.

When using HP Tuners to disable the codes completely via the diagnostics menu, the ECU still commands "0", even more interestingly when using the Tech-II to command the phaser states I get a failure due to codes present as if it is setting any of those codes, however when I use the T2 to scan for codes, none found.

So clearly the ECU is still checking, and setting these codes, then acting on that information to disable the T2 manual command mode, and during normal driving always commanding "0" for all phasers it is just not reporting those codes through the OBD interface.

My question is: Is it possible to change the ECUs OS such that it never runs the test to trigger these "internal codes" (or ignores the tests output) and always operates the VVT system normally, even if problems are indicated?

Any ideas?

[KillboyPowerhead]

Did you disable those codes while they were active? If so, I wonder if disabling the codes when they're not active would prevent the VVT being disabled - can you get the engine back to a state such that those codes won't be present?

[carperson]

Did you disable those codes while they were active? If so, I wonder if disabling the codes when they're not active would prevent the VVT being disabled - can you get the engine back to a state such that those codes won't be present?

When the calibration is flashed it erases the codes and any "phantom code" as I'll call what I'm talking about. It takes a little while of idling for either the real or phantom codes to set.

I believe that VVT is active (just temp disabled as per the normal tune) for the first few seconds of the first start in both the stock and code disabled tune, then in both the ECU disables the system, but simply reports everything as good in the code disabled tune.

Are there any HP Tuners staff on here that can shed light on what/how exactly HP Tuners does to change code enablement?

[carperson]

Ok, doing more research it looks like what HP Tuners is doing is setting a DTC Disable "MASK" parameter, which tells the ECU not to communicate the DTC, but still act on it internally. E.g. enable the limp modes described above.

What I need to set is figure out a way to adjust the CKP CMP error band parameter.

Does anybody have any recommendations for a tuner service that could do this?

[enmanuelpimentell]

Could you post the tune so we can help you further?

[carperson]

Could you post the tune so we can help you further?

ctsdefaulttune.hpt

Sure, see attached. Didn't notice you had replied until now!

Attached is a factory tune. Per my research since posting: Changing timing DTCs to disabled does not effect the internal test conducted, just disables the communication of the DTC to a OBDII scan tool and illumination of the SES.

I think to take this further I need a custom user defined definition created for the data that changes the maximum correlation error band between the CKP and CMPs.

Of course most tuners don't really go this deep technically, so it's a bit of a road block.

Per GM SPS: calibration 12628463 is the original start of production, and calibration 12644338 has had the error band I am talking about adjusted to allow a slightly higher error before failing its test and setting DTCs.

I would imagine comparing the two calibrations would yield the location of this parameter to set in a user defined definition in HPT.

Let me know if you have any ideas, thanks.