LS1TECH - Camaro and Firebird Forum Discussion - PCM Diagnostics & Tuning

Transient P1133 Failures (Tech 2 History) After SLP Lid Install & Trim Reset

Ape Man — Tue, 19 May 2026 10:05:11 GMT

Hey guys,

Looking for some insight from anyone who has chased transient O_2 switching speed monitors on legacy GM Gen III PCMs (specifically a 2002 LS1 F-Body operating system).

Background: The car has never had a pending or confirmed code stored in its life. I recently fixed a minor vacuum leak connection at the AIR pump solenoid, installed an aftermarket SLP air lid with a smooth bellows/cold air pack, and performed a full fuel trim reset.

Since the reset, I�ve noticed two isolated "Fail" ticks on the Tech 2 history scoreboard for P1133 (Bank 1, Sensor 1). However, the overall counter has 14 clean passes, and it has still never tripped a pending code, a confirmed code, or illuminated the MIL on the dash. I know it's a Type B code requiring consecutive trip failures, so the software is filtering it out, but I�m trying to nail down the exact root cause of the micro-events.

The Two Isolated Failures:

1 Fail #1: Occurred early on during the initial learning drive cycle right after the trim reset. Ambient temperature outside was cold, right around 3�C.

2 Fail #2: Occurred the other day following a warm restart. I sat for a few minutes, fired it up, and immediately drove right out onto a high-speed highway, followed shortly after by a long coast down a big hill.

The Data Logs:

When I dig into the actual scanner data, the execution parameters and raw sensor operation look immaculate.

Voltages & Range: Both front sensors have fantastic amplitude, hitting full rich (near 1.0\text{V}) and sweeping clean down to full lean (0\text{V}). There is zero lazy scaling or chemical contamination.

Switching Frequency: Warmed up in Closed Loop, they are tracking beautifully right together, averaging a crisp 31\text{--}33 switches per minute.

Fuel Trims: Intentionally tight and well-balanced across both banks. My stabilized Long-Term Fuel Trims (LTFT) are locked in solid, hovering cleanly around 7.8\%\text{--}9.4\% at standard highway cruise and tracking tightly between 6.1\%\text{--}7.3\% at idle. Total fuel trims are averaging perfectly right around 8.5\% on Bank 1 and 7.9\% on Bank 2.

My Theory / Question for the Forum:

Since both front sensors are identical, brand-new denso units, I'm leaning toward this being a purely environmental/thermodynamic byproduct rather than actual hardware degradation.

My thinking is that the SLP lid pack is flowing a significantly denser, higher-velocity, colder fresh air charge into the cylinders at low-load cruise. On a cold 3�C day�or immediately following a warm restart before the physical under-car steel is completely heat-soaked�this increased cold airflow drops the baseline exhaust gas temperature just enough to chill the sensor element.

Furthermore, I suspect that long coast down the hill right after hitting the highway played a major role in Fail #2. Dropping into a prolonged coast right at that transition cut the thermal input to the exhaust drastically while cold air was rammed down the pipes and under the car. When the PCM monitors its timing windows, Bank 1 misses the lookup table's switch target by a fraction of a second, ticks a single fail, and then spends the rest of the day racking up perfect passes once fully hot.

Have any of you calibrators seen the SLP lid/cold air packs consistently shift the thermal blueprint enough to trigger transient P1133 history notches on light highway transitions or extended coasts? Should I expect this to occasionally pop up as an environmental fluke under these conditions

LS swap Idle Issue

LSleeper1500 — Tue, 19 May 2026 03:33:02 GMT

Hey guys. Trying to get some help. LS swap is almost done and I�m struggling getting truck to idle. I am seeing P2138 which corresponds to D/E. 2012 E38, truck OS. Truck will attempt to idle and RPM will randomly jump RPM. Sometimes 5-10 seconds after trying to idle, others 30-45 seconds. Which I think then goes into limp mode.

most of the data I see refers to high resistance. But all 5 pins at the pedal connector back to ECM have 0 resistance. I�ve also pulled in a couple channels for throttle and pedal that I�m attaching to see if I�m missing anything. Only thing weird I noticed when pinning power is pin C (5 Volt Reference) fluctuated randomly when pinning power. But settled at 5.03V. D also measured at 5.03V

not really sure what else to go from here. For what it�s worth, throttle body is a new NW103, and I have. Ctsv2 pedal and also a 2012 truck pedal since the file is 2012 also.

any help/troubleshooting is appreciated

Attached Files

IMG_6082.mov (13.54 MB)

Another flex fuel enable problem post

QuiknBoosted — Fri, 15 May 2026 22:41:28 GMT

Hello yall, had another account but ider what the username used to be so new account and here we are....

2003 Silverado 4.8L 4L60e with DBW p59
The OS is 12593058

VCM scanner shows 0% even with 20% ethanol in the tank

I have the "enable" feature turned on with DTCs. I found an old thread referencing using Tuner Cat to enable ff in certain p59s as not all data is there in the OS. That's a bit beyond me though with writing a COS like that...
I also believe segment swapping was another option, but I can't find an OS file with factory FF to use. I've attatched the current bin file below.

Would also like to note I am still using an old laptop with MPVI1 (YES MPVI1 in 2026!). I do have the lastest hpt software installed, but perhaps i need to finally upgrade to the latest mpvi, especially with support ending for the mpvi1 soon here.

Attached Files

03 RCSB Reno Tune 2 FLEX FUEL with 160 TRANS BLUECAT.hpt (256.9 KB)

Looking for Tune - Lost Orginial

weedoublewide — Wed, 13 May 2026 14:39:26 GMT

Had to put my ls 6.0 swap on the side burner for a few years, however ready to get back at it. However, I lost my original tune, had it on my computer and the harddrive died. Shame on me for not saving and resaving 10x. The engine is for a LS 6.0. It came out of a 05-06 Chevy Silverado with a manual transmission, most likely the nv4500. Reason is I've made some modifications and would like to start fresh.

I have checked the tune repository at hp tuners, all they have is the tune for automatic transmissions. While I can check all the tables and get it as close as possible, I would like to ask the community if anyone has a original tune first.

Thank you,

double

Help Disabling Rear O2 Sensors

Bonez0413 — Mon, 11 May 2026 20:20:23 GMT

Just installed catless long tube headers on my 5th gen Camaro SS, added a wideband, and removed the rear O2 sensors. I�m trying to get rid of the CEL using an MPVI4 with the latest version of HP Tuners.

From what I�ve read, older HP Tuners versions supposedly allowed you to disable the rear O2 codes, so I tried going that route, but I ran into another issue the older versions of VCM Suite don�t seem to communicate with the MPVI4 interface.

Has anyone with an MPVI4 found a working solution or workaround for this? Trying to figure out the best way to handle the rear O2/heater circuit codes on the newer software.

Backfire!! Flame!!

Perry LaBarbera — Sun, 10 May 2026 01:29:48 GMT

Hey

I have a LS3 swapped Porsche, track only car. Terminator X Maxx, runs great EXCEPT on closed throttle backfire on decel, usually above 5000 rpm, plus, after a strait away, long or short, BUT ONLY out right side cylinders 2,4,6,8 side. So much that the right exhaust is white, drivers side black. I am told it puts out a flame, right side only, many drivers have seen it, and it did blow apart a set of Flowmater 40s last year, guts rattling around and cases clearly bulged out. I swapped all left and right injectors, same thing, swapped plugs and wires left to right, same thing, O2 sensor is on the left. Exhaust pipes are not joined in anyway..IDEAS????

LS3 will not run

LSharold — Thu, 07 May 2026 17:11:16 GMT

I have an LS3 engine that has been running perfectly until now. Suddenly, it dies 2�3 seconds after starting. Could it be that VATS has been activated? I�ve done some electrical work, but nothing involving programming. Could it be a grounding issue? (I can't find anything obviously wrong) Thanks for any help, Harold

99 trans am, P0336 crank sensor code

TKR88GTA — Thu, 07 May 2026 11:59:00 GMT

At a loss here... 99 trans amPic for attention... Swapped a gen 4 6.0 into it, engine builder swapped reluctor wheels, the extension harness for the cam sensor outside wires, the car cranks but only fires on 2 maybe 3 cylinders (5 and 8, with 3 being slightly warm to the touch compared to the other 2 are super hot, other than that the rest are cold to the touch) if I give it throttle it'll stay running but sounds like a tractor. I've checked spark with a good ole screw driver while someone was cranking, I've checked injectors with noid lights and they light up, cleaned injectors.

Out of stuff to check aside from having the oscilloscope. For the cam and crank sensors. I've checked..Injectors for being plugged and cleaned them, injectors are getting the signal with the noid lights hooked up

Spark plugs are firing, injectors and coil plugs are on the correct sides, verified I do have the 24x wheel (only thing I can't confirm in vehicle is orientation of it being on correctly), I do have the 1x cam timing gear with the half moon facing the sensor. The sensor is a Delphi sensor, I did swap the wires to make the signal and power correct on the sensor side of the connector. I've swapped crank sensors with my other car that was running. So not crank sensor. I do get a p0336 code when car does decide to fire. Power and grounds are ok there. Symptoms have all stayed the same.. firing on #5 and 8 cylinders while the rest are cold to the touch.

I guess one last thing to mention is that it did start and run just fine before I parked it. Original LS1 had a knock and why it got pulled.

Accuracy/resolution- small pulse injector dutycycle

Full Power — Fri, 01 May 2026 20:53:12 GMT

Question of how accurate the fuel calculations/ observed injector duty cycle is at low loads and idle conditions.
Can one MEASURE actual total fuel flow with any accuracy with injector duty cycle at idle or cruise conditions?

Anyone ever attempt direct reading fuel economy MILES per GALLON, derived from injector flow x duty cycle x rpm x (constant) ?

Does small pulse adders, minimum pulse duration get added in the pcm, or are these factors included in displayed Injector duty cycle?
.
A channel to display, or LOG calculated fuel consumption rate would be pretty cool.

Incomplete tune?

Ewreckt — Fri, 01 May 2026 00:28:12 GMT

Sup boys hope this is the right spot. Just bought an 02 rcsb 5.3/4l60. Truck has a cam, longtubes and does appear to be tuned, but i have no clue which cam or if it has any other supporting mods. I know enough to pull the tune file and compare to a stock file, but it looks like the tune was never completed. P0103 code from what I know is usually a deliberately failed maf sensor for the tuner to focus on speed density tuning. Ultimately I need this thing tuned properly, but there are other issues with the truck I will need to sort out but I want to make sure the current tune is good enough to not cause other issues. At the moment it will run and move under its own power but will try to stall in gear when letting off the gas. Also haven't gotten it in any other gear than 1st and reverse. I'm prepared to put money in this thing and planned on starting with the transmission, but id hate to blow up the new one and find out later that the tune was dogshit. Any help is appreciated and im happy to pay for the time of a professional thats willing to work with me a bit on the tuning process to make sure I get this thing sorted before I cause more issues than im fixing.
thanks!

Attached Files

stockgreentruck1.hpt (237.3 KB)

LS1 Starts then Dies

Clayton_5 — Wed, 22 Apr 2026 20:18:15 GMT

Hello,

I recently built my first LS for my 1998 Camaro SS, but I'm having major issues getting the motor to idle. I've tried many tune adjustments to get it to work, but I haven't had any luck. The car will crank and start perfectly fine, then die 1-2 seconds later. There are a few things I've noticed happening:
-IAC circuit is almost maxed out at ~175 steps compared to a desirable 40-60 step
-As timing ramps in from 0deg to 18deg, RPM drops and eventualy the motor dies
-Me operating the throttle will not keep the motor alive; opening the throttle drops RPM. When the throttle closes, RPM increases slightly
-Sometimes RPM seems uncontrollable and will shoot up to 3000RPM, then dies

I'm thinking this is an issue with the size of the idle air circuit(Too small for the engine), causing the IAC to be open +170 steps. I can adjust where the throttle blade stops, but the adjustments seem to make no positive change. Would anyone be able to point me in the correct direction?

I've included a image of my datalog, datalog file, and tune file. I've copied the LS2 injector data onto this tune as best I can.

The build is as follows:
~10.0 Compression Ratio
BTR Stage 2 V1 NA Camshaft
AFR 230cc CNC ported heads
LS2 Intake
LS2 Injectors
103mm Chinese throttle body
Long tube headers
AEM WB02 30-0300 tied into the EGR circuit
Hp Tuners MPVI4
Other sensors or things I didn't mention are stock(MAP sensor, MAF sensor, etc)

Attached Files

Stock Camaro Tune plus INJ.hpt (216.7 KB)

Stock tune plus INJ.hpl (5.3 KB)

Code P101

totop73 — Tue, 21 Apr 2026 03:11:48 GMT

I have a73 Corvette with a 2002 LS1. I installed a 5 wire Maf sensor. I keep getting a code P101 and sometime it the engine seems to kind of a burp when driving down the road. I changed the Maf sensor and ordered a new harness that is for the 5 wire sensor .Is the tune different for a 3 wire to a 5wire sensor ? Anybody have the answer? Thanks Charlie.