Service Engine Soon after ECU swap

[leomio]

I have a 2005 GTO with an LS2, modified with supercharger, cam & full bolt ons.

The car was having issues with it going into Safe Mode sporadically. Tuner decided the ECU was part of the issue so I was able to track down a refurb'd one on RockAuto and it was swapped. It functions in the 6.0L LS2, but it was from a 5.3L GM truck.

So far, it runs just as before, but every time I start the car, the Service Engine Soon on the tach display. A push of the reset button makes it go away and it never comes back while driving. I've tried disconnecting the batter and the three-pedal stomp method, but to no avail. Tuner says he's stumped as to what's causing it. Any ideas?


Also, the has gone into Safe Mode even after swapping the ECU. Code P2135 Throttle/Pedal Position Sensor/Switch A/B Voltage Correlation. I've changed out the throttle body, the pigtail to the throttle body, I've gone thru two pedal assemblies (drive by wire) & cleaned the MAF prior to giving up and bringing it to my tuner who suggested the ECU swap. Any ideas where else to look to chase down the culprit? I saw something about increasing the values that an error is tripped to its maximum value, especially on heavily modded cars. Would this be beneficial? I suggested it to my tuner but he stated that was just putting a bandage over the problem ... but I may just have him do it regardless when I bring it back.

I just want to have things to suggest when I do bring it back in rather than hauling the car back and forth to him.

Thank you.

[blindsquirrel]

How was the replacement ECM reprogrammed? Is it the same service number, and correct for your GTO VIN? Was it set up correctly after install/programming?

[eXo3901]

Already asked for relevant info on ls1gto. Seemed like the tuner just changed the vin and copied parameters over. It needs to be SPS?ed after we find out the service information. All was already mentioned on the other site.

[blindsquirrel]

Oh, so this is somebody shopping around until they find an answer they like?

[leomio]

More just trying to get a different perspective and look into different avenues to rectify the issue with my tuner. I'll be contacting him this week to set-up bringing the car back and would like to explore all possible areas to have him look into. If that offends, that wasn't my intention. I'm in no way even remotely knowledgeable on tuning, so I don't even know what to bring up as possible solutions or things to look into to him.

LS1GTO did advise to ensure the Service# is the same.

The vehicle was programmed to the factory calibration with GM MDI 2 and my VIN was purchased from GM and installed on the new, refurbished ECU, immobilizer and crank relearn done and then the custom tune for my modifications from saved files was uploaded to the new ECU. When I call, I'll have to ask if the service numbers are the same. Aside from the Service Vehicle Soon error at start-up, the car runs just as before with no hiccups, minus still having the Safe Mode issue.

If the Service #'s weren't the same, would the new ECU even work?

My tuner did state that the operating systems were different from my original ECU to the new ECU ... the original being programmed to "Crank" signal whereas the new one from the 5.3L ECU was "Frequency" signal. When my tuner used the original "Crank" setting, the Service Vehicle Soon error didn't pop up, but the RPM tach didn't work. When he switched it to "Frequency", the tach works as it should, but the SVS error pops up at every start up.

Any ideas besides ensuring the service #'s match to look into?

[GHuggins]

Did Rock Auto program the new ecm to the vin in the old ecm and is a separate tcm involved? I've seen issues just like this on newer gens where it was just an OS break point issue. 15's and 17's for example I know had 3 completely different OS's in their corresponding years and if you didn't match them correctly they would have cel's on startup that you could clear, but would immediately come back on the next startup. Usually pertaining to baro or something weird like that, so if a separate tcm is involved it needs to updated at the same time via tis. If not then make sure it was programmed to the previous vin.

[blindsquirrel]

GTOs are weird.

ECM Replacement

If the engine control module (ECM) is replaced, the following procedures must be performed:

Program the ECM --Refer to Service Programming System (SPS) .
Link the ECM to the Powertrain Interface Module (PIM). The ECM must be linked to the PIM using the Techline Information System (TIS).
The CKP Variation Learn--Refer to Crankshaft Position System Variation Learn .

To do this, somebody somewhere would have to use GM (or equivalent - Autel, Snap On, etc.) tools. And same for the programming. HP Tuners cannot properly change the OS on Gen 4s, there are two segments that don't get read or written.

[eXo3901]

The vehicle was programmed to the factory calibration with GM MDI 2 and my VIN was purchased from GM and installed on the new, refurbished ECU, immobilizer and crank relearn done and then the custom tune for my modifications from saved files was uploaded to the new ECU. When I call, I'll have to ask if the service numbers are the same. Aside from the Service Vehicle Soon error at start-up, the car runs just as before with no hiccups, minus still having the Safe Mode issue.

My tuner did state that the operating systems were different from my original ECU to the new ECU ... the original being programmed to "Crank" signal whereas the new one from the 5.3L ECU was "Frequency" signal. When my tuner used the original "Crank" setting, the Service Vehicle Soon error didn't pop up, but the RPM tach didn't work. When he switched it to "Frequency", the tach works as it should, but the SVS error pops up at every start up.

These are conflicting statements. If it was programmed correctly, as hinted in the first paragraph then the crank signal would not be an issue. The OEM reprogramming would set the correct value.

The SVS issue sounds like the PIM/ECM/BCM linking was not completed, VATs was disabled, and codes turned off. (If you do not have your security codes for this car, this will never go away.)

The service number stuff is just to confirm the ECU you have can actually accept a factory calibration for your vehicle. So, when we find out which operating system is currently on the computer the correct recommendation can be made to either, 1.) reprogram properly with correct GTO operating system 2.) purchase a compatible service number ECU and then reprogram that one. 3.) other.