Reduced Power Mode at WOT (tried everything) - LS3 swap with pedal assembly

[Joe6pt0]

I've tuned many cars with DBW and have successfully disabled Reduced Power Mode on many vehicles via P0068, PO121, P2101 disabling. I've even disabled DTC 1516 as it was previously setting. This one has me stumped as its still enabling only at WOT or close but not only at high RPM. I can get this to fault going 45mph with lockup engaged and flooring it. On a select few vehicles I've had to go in and scale the tune down to lower the max VE values a few times to get this completely gone but on this vehicle I've tried to scale virtual VE by 75% yet it still enables quite easily.

Details: LS3 engine with mild cam, 4l60E trans, 08 Tahoe ECM, unknown TCM, pedal assembly from either Tahoe or vette (another shop did the build). It's a complete swap so there is no BCM just ECM/TCM. I was going to try to scale down 50% from where I'm at to give that a try but figured I'd throw it up here in case I'm missing something.

DTCs present (Even after disabling) are:
U0100 Loss comm with ECM/PCM A
U0121 Lost Comm with ABS
U0140 Loss comm with BCM


Attached tune is a virtual VE scaled by 75%

OL11b scaled.hpt


I've considered playing with the Engine->Airflow->Electronic Throttle->Desired Throttle Area sections but most have warnings that have me worried.

Anything stand out that I'm missing?

[Joe6pt0]

I'm going to try 50% scaling to see if that corrects it.

[dlc_racing]

Just to get everything cover is that wiring in good shape? I have tha same issue in a 2009 silverado with a 6.2 swap and a tvs magnacharger in the end the trouble was a defective cam sensor connector that was making false contact and as soon as the pcm lost the signal send the truck to RPM it took me a while to get to the fault and the bitch never gets me any cam sensor dtc's or any else just my two cent men good luck

[Joe6pt0]

Thanks, yes the wiring is all brand new and has been gone over. I think I've found the issue and will post results later.

I was able to view the scanner with the engine off. As I approached what felt like 100% throttle, I would see the max 88% on the scanner but the pedal still had a good 1/4 of travel. After this point, the TPS reading would get lost and default to 0 (actually 27%) and would not respond at all. I adjusted the max rotation position to 90% in the cal and after that point I don't see this dropout. Looks like I'm on to something here, but HP Tuner's warnings about "incompatibility of this calibration with vehicle TAC module may render PCM permanently inoperable" had me worried about modifying it. I'd also like to adjust the "Desired Throttle Area->Map A - Normal" table as well but the same warning is present.

[frankstd]

I had that Issue with a swap and found that the way the throttle pedal was mounted was allowing the pedal to travel more than it would and it should when on the stock vehicle.
I made a pedal stop so that the pedal would just get to WOT and stop.
(in the beginning I tapped couple of coins quarters together onto the firewall with ducktape) checked with the scanner how much throttle % I had and made sure it would stop after 100%.
after figuring the thickness of the stopper needed to be I made one out of aluminum and fastened to the firewall.

[gmtech16450yz]

Your desired throttle area table doesn't look like it's from an '08 Tahoe. It looks more like a table from an LS9 or LS7 than anything else. It's almost identical to an LS9 table actually.
So don't be afraid to change it since it's already been changed from an '08 Tahoe. The way these tables go is the higher the stock hp, the lower the throttle percentages (below full throttle/pedal) will be in this table. The pedal percentage table you're running in this build is way too conservative for an NA LS3, it probably makes the throttle response kinda flat anyway. Look through the tune repository for a tune from an NA LS3 or better yet, from an actual '08 Tahoe with a 5.3, 6.0 or 6.2. You'll see when you compare to the one in your tune that the truck tables are actually way more exponential in the mapping. The table you have is very flat until full pedal travel. That's the way you'd want a boosted or high hp engine setup.

On the early ECM's this table was known for killing ECM's, but I've never killed one in the later OS's and ECM's. The worst it will do is exactly what you're experiencing, a reduced power mode at certain pedal positions. That's why I'd look at that table and put the rotation table back to 100%. I believe the problem is the mapping in the pedal percentage table is not compatible with the ECM/OS/pedal combination you're using.

Hope that helps!

[kgraves]

double check what type of pedal you are using. If i remember correctly, the APP wiring was slightly different between the truck and car. Im not sure that would cause reduced power conditions but it does cause throttle issues.

[HartRod]

The vette and truck pedals have 2 wires that need to be swapped. When you say TCM, are you talking about the tach module? I thought only the A6's used the TCM (located in the tranny)?