No throttle response

[LS XJ]

Hi guys

Well I thought I had the SD tune done. Today I was running errands and about 30 minutes in I shut it off for about 2 minutes. It had been running great.
I started it up and it idled at 1300 RPM with no throttle response. My WB was off the charts lean. I didn't have my laptop with me so I was planning on having my son bring to me. While I was on the phone I tried starting it again and this time it responded normally. I drove it around for about an hour with no problems.

This evening it had sat for about 2 hours and I wanted to bring it into the shop. It started up fine and ran fine. I shut it off in the shop, then realized I needed to move it back a few feet.

It started the then a 1300 RPM idle with absolutely no throttle response. (Drive-by-wire)

I know if I flash an older tune into it, it will run.

I've attached the tune I've been running, the scan log of me driving it around today, and a short scan log of it running with no throttle response.

I sure could use some help here, it has me stumped.

EDIT: Sure enough after I posted this it started and runs fine. I can't trust this now.

Thanks

[LS XJ]

I'm wondering if I might have a hardware problem. This has happened 3 times, all when I tried to restart hot. All times it did restart and run fine if I left it. Possibly reflashing was just a time to cool down.
I should have checked for codes. My CEL is on all the time because I was SD tuning, so I wouldn't know if a new code came up or not.

I'll have to see if I can recreate the condition and be ready to look closer.

I believe that I read somewhere online a while ago about 2003 Chevy trucks with DBW problems, and an replacement TAC is used.

[LS XJ]

So this morning I checked for codes. I have a P154
I guess that reveals a "Reduced Power" situation.

I've researched and this can be attributed to air flow higher than expected. I'm running an SD tune, no MAF. The PCM uses the MAF to calculate air flow when presenting this code. I've read about upping the air flow in the 1514 table, where do I find that?

This is a stock 6.0 engine, just an LS1 intake and shorty headers. Is it actually flowing that much more air?

EDIT: Now that I think about it, I did swap my Envoy 5.3 MAF with my 6.0 MAF when trouble shooting. It drove the same back then for the problem I was working on so I just let then swapped. This P1514 has come up since then.
I'm going to swap them back and see if the P1514 condition returns.

EDIT: So, considering that the tune is an SD tune, I don't really need the MAF at all. If it's tuned out, it really doesn't use any MAF airflow info then, does it? So if I have the wrong MAF in there, as long as the IAT values are correct it won't matter.

[LS XJ]

OK, so I can replicate this condition.

It only happens are I have run a WOT, high RPMs. It runs fine for the rest of that drive cycle, but if I shut it off and restart it, it has no throttle response and has a P1514 code. I shut it off and wait 30 seconds and it starts and runs fine. If I just drive it with no WOT it will run fine the next drive cycle.

It is WOT that triggers the P1514. Can I adjust something to compensate for this? What's with the "1514 table" that I read I need to up the values to prevent this?

Thanks

[Sin7even]

Some info related to code P1514.

Possible causes:
- Faulty Throttle Actuator Control (TAC)
- Throttle Actuator Control (TAC) harness is open or shorted
- Throttle Actuator Control (TAC) circuit poor electrical connection
- Faulty Mass Air Flow (MAF) Sensor

If you think module is still referencing your MAF you definitely will want to have the correct MAF connected, or make sure that the module is failing the MAF so it will go in SD calculations.

Looking at your file, if looks like you have set the module in SD correctly. Only thing you might want to change is the Engine Diag> Airflow> Mass Airflow Sensor> MAF Frequency Fail High: From 0 Hz to some thing like 5 or 10 Hz (0 Hz is suppose to work, but I have read of people sometimes running into problems with settings being set to MAX or MIN).

Maybe someone else can chime in and give some thought on the following. Engine Diag> Airflow> Mass Airflow Sensor> Maximum Delta Airflow - P0101 Error: Might try setting the Airflow Delta to something like 1 or 2 across the table. Should help set P0101 code, and maybe that would help you.

[5FDP]

People that boost their vehicles always just raise the P1514 table in the engine diag tab, most just max the whole thing out to stop it from going into REP mode.

I'd just double the whole table and see if it stops.

[Sin7even]

OK, so I can replicate this condition.

It only happens are I have run a WOT, high RPMs. It runs fine for the rest of that drive cycle, but if I shut it off and restart it, it has no throttle response and has a P1514 code. I shut it off and wait 30 seconds and it starts and runs fine. If I just drive it with no WOT it will run fine the next drive cycle.

It is WOT that triggers the P1514. Can I adjust something to compensate for this? What's with the "1514 table" that I read I need to up the values to prevent this?

Thanks

How high are your RPMs at WOT? Does it happen only after High RPM/WOT run and shut down? Wonder what happens if you try to replicate the problem, but only get the engine to rev up to 5000 RPM (do everything else identically). Maybe the fault code is being set from going to WOT?

[LS XJ]

It does ONLY happen when I've gone WOT in a drive cycle. It drives the whole drive cycle fine, just when I restart it shortly after shutdown. If I let it sit 30 seconds it starts and runs fine. The code remains.

I tried maxing out the 1415 table and it DOES solve the "no throttle" issues, but creates another one. I have a very long throttle decay. If I poke the throttle, say to 2000 RPM it hangs about 5 seconds, then begins a very slow decay to idle. Very annoying while driving, it doesn't slow down when I take my foot off the gas.

I then tried just adding 1.0 to the entire table. Same as above.
I then tried adding .5 to the table above 80% throttle. It drove fine, as it should, however, it now reverted to the 1514 problem again.

I'll have to see what other options I can find.

Not going to have anymore time to spend on it today.

Thanks for the suggestions.

[Sin7even]

Now that I think about it, you have been having odd throttle related problems for a while now. If I remember correctly you have had a few threads open.

"I believe that I read somewhere online a while ago about 2003 Chevy trucks with DBW problems, and an replacement TAC is used"

Do you have the original donor vehicle TAC module, or did you get a replacement? Are the TAC module, Throttle Body and Throttle pedal from the same donor vehicle?

[LS XJ]

Yes, the whole swap is from the same donor vehicle.

The throttle issues began once I began tuning. I drove it many KMs on the stock tune and it drove like factory. Once I began tuning the VE in SD the idle problems began. I solved the majority of them by tuning out the Throttle Cracker.

Then this 1514 showed up. If I flash the stock tune (with MAF) the truck drives great, lots of power, idles smooth, drives smooth, shifting is smooth, but the VE was way too lean.

It does not like not having the MAF enabled.

[Sin7even]

Post a copy of your original read file that you were able to drive the vehicle around with before the throttle issues started.

*EDIT
Found one of your older files you posted before you started tuning SD in one of your first posts. Comparing both of the files I do not see any changes in the file that would cause you problems.

Have you tried reflashing the module back to stock (when you didn't have throttle related problems), and then start tuning things one thing at a time? Also another option would be to perform a throttle learn (some vehicles have a THROTTLE or IDLE LEARN in the scanner controls), for the rest of the vehicles people have used other work arounds.

Read this thread for throttle learn options:
https://www.hptuners.com/forum/showt...an-you-do-this!!

[LS XJ]

Hi

I'm going to flash my stock tune and start from scratch. I hadn't made the connection to the WOT on a drive cycle and the no-throttle issue until recently.

I'll now go step by step and checking each time for this 1514 to return.

At least I know that I can recreate the issue on a drive cycle.

[Sin7even]

Sometimes starting from scratch can be a quicker option. If you end up having your original hanging idle issue again (the one you corrected by disabling the Throttle Cracker), I would then just disable the Throttle Crack without any other changes and drive the vehicle for a few drive cycles to make sure everything is correct before you go any further.

[LS XJ]

1st run
So the stock tune drives great, smooth, lots of power, idle (600 RPM) behaves itself. LTFTs are over 25% lean but WB reports AFR is OK. No 1514 issue.

2nd run
I zero out the MAF, DTCs are set to error on second. Idle RPMs are 650 now and decay is slow. Drives "good", shifting is harsh and WOT shifts are about 500 RPM early. No 1514 issue.

3rd run
I copy the high octane table to the low octane table. Idle RPMs are 650 now and decay is slow. RPM jumps up when manually shifting through PRND. Drives "OK" but less power, shifting is harsh and WOT are about 500 RPM early. 1514 issue is present now.

So where do I go from here? It seems to really need the MAF.

I'll try the stock tune now with only the spark table copied. That seemed to be the final change that brought back the 1514

[Sin7even]

"2nd run
I zero out the MAF, DTCs are set to error on second"

I would try setting the MAF Frequency Fail High to some thing like 5 Hz or 50 Hz (something very low, but not bottomed out to 0 Hz), and you want your DTC/SES MAF codes set to error on 1st.

IF you only had one drive cycle in your second run, you would have still been referencing your MAF.

[LS XJ]

"2nd run
I zero out the MAF, DTCs are set to error on second"

I would try setting the MAF Frequency Fail High to some thing like 5 Hz or 50 Hz (something very low, but not bottomed out to 0 Hz), and you want your DTC/SES MAF codes set to error on 1st.

IF you only had one drive cycle in your second run, you would have still been referencing your MAF.

Thanks. I just disabled the MAF as you suggested, set to 5 hz. Ran "Good", as I described previous, better RPM behaviour, until I copied the high octane to the low octane. It runs real strong then, but a restart and I get the 1514 again.

????

[Sin7even]

I'm assuming you still had the MAF codes set to error on 2nd, if so that is why it took the second start to get 1514 to set again.

If MAF P0101, 102 and 103 are still set to error on 2nd, set them to error on 1st.

In regards to the 1514 setting, I would try what 5FDP said earlier:
"People that boost their vehicles always just raise the P1514 table in the engine diag tab, most just max the whole thing out to stop it from going into REP mode.

I'd just double the whole table and see if it stops."

Or, maybe just add like 10% to the P1514 tabe at a time until it stops setting the P1514 code and going into REP mode.

[LS XJ]

This last tune has the DTCs set to MIL on 1st error.

I did play with the values in the 1514 table and it nothing but screw up the RPMs.

I'm thinking I will just proceed to MAF tuning, hoping that with a MAF and 2 octane tables to use it will be happy and not do a 1514 anymore.

I've just now set up an AFR Error for MAF tuning. Debugging my setup so It will display in the hist properly.

[Earwax]

Check the freeze frame and failure records.
They are available until the code is cleared.

The PCM detects that the difference between the actual airflow (MAF) and the Speed Density calculated air flow is more than expected.
The above condition is met for less than 1 second.

[Earwax]

Check pin "C" (blk/wht) at MAF for GND.
Also check pins "24,27,64,67" at PCM "C1" for GND.
The MAF and O2 sensors share the same GND.
Make sure that the MAP connector/line is not leaking.