LSx Lessons Learned.

[jorgensensc]

I thought I would write this so others that are performing an LSx swap will have some important info that will help them on their conversion. These are my observations and may not be true of every swap out there. Please feel free to add any info that you find valuable from your own personal swap adventure.

MODS: If you want you can make this a sticky that others can add to if you feel it will be a valuable addition to the board.



Some of this applies to everything, but some is engine/trans specific.

For ease of installation get the engine,trans,ECM,and pedal out of the at the very least the same year vehicles. The same vehicle is best.

6.2/6l80e
Somewhere in 2010 the e38 ECM operating system changed (OS). Make sure your ECM matches the trans computer (TCM) year for sure or the two will not communicate correctly.

The TCM can be exchanged between trans, but the valve body operations changed between years so they will have to be switched also. Much easier to just change ECM to match TCM.

Trying to overwrite a different OS onto a different year ECM will result in failures. Sometimes instant, sometimes glitches that cannot be resolved. Do Not do this! Just get the right year ECM.

The 6l80e needs the TCC wire GROUND when brake pedal not depressed, 12 volts when brake pressed. You can tap into the brake wire on the brake switch to accomplish this easily if you have regular brake light bulbs. If you are using LEDs then you need to set up a relay and use a 1k ohm 1/2 watt resistor to pull down when pedal not depressed. As I have learned, YOU MUST HAVE A GROUND WHEN PEDAL NOT DEPRESSED. An open circuit will not engage the TCC.

Early 6l80e trans received the TCC signal directly from the brake switch and from the ECM over the CANBUS system. Later 6l80e trans receive the TCC signal by ECM via CANBUS only.

Verify the function of the Body Control Module (BCM) in your donor vehicle. You may or may not need this depending on what functions you want to retain.

There is some debate about this, but there may need to be a 120 ohm terminating resistor put after the trans, and before the Data Link Connector (DLC). The CANBUS system needs to see this so there won't be any communication errors. The BCM from your donor vehicle usually has this in line between the trans and DLC. If you measure the voltage on either the high or low wire and it is 5 volts then you need the resistor. The voltage should be about 2.5 volts. Just put a resistor between the high and low wires.

After market harness are great, but not necessary. Modifying the stock harness is very doable and not that difficult. If you want the ECM mounted somewhere special then you may want an after market harness.

LS3 and L92 engines are not quite the same. The engine harness and sensors are not identical. Make sure you have the correct harness for your ENGINE.

A subscription to ALLDATADIY is a must! Spend the couple of bucks, it will help you find any issues you may encounter.

Buy a decent scantool to help you diagnose problems.

As a member found out, tuning with open headers will give you many errors and have you chasing ghosts. Get the exhaust done before fully tuning.

Hire a reputable/reliable tuner. Nothing beats a dyno tune. Mail order tunes are great for startup. If you have the time to learn it buy HP Tuners and tune/ learn yourself. Be wary of Craigslist tuners. Most of them bought HP Tuners and know a just enough to be dangerous. Or can only tune stock vehicles. Any kind of conversion/hybrid will baffle them. They are trying to recoup their cost and learn on your vehicle. Decide if your ok with that.

VATS MUST BE TURNED OFF TO START THE ENGINE! If you have double checked everything and it all checks out, have your tuner verify they removed VATS. not that he remembers disabling it, but have him verify. VATS can be disabled, but if the tuner doesn't REWRITE ALL then it may not take. You will chase ghosts forever and never get the engine to fire. The engine may start up and run for a few seconds, or it may not start up at all.

Custom fuel tanks are very nice and convenient, but not the only option for fuel tanks. In tank fuel pumps are best. There are many options.

At this time there are no DLC splitters that will let you hook up multiple scantools/gauges. One will overrule the other so you will only have one tool work at a time.

CANBUS gauges are great and convenient. However the verdict is still out as to whether or not they effect the ECM. They are not supposed to, but there are GM Technical Service Bulletins (TSBs) that claim add on devices are causing issues (scantools, insurance devices to monitor driving, etc).

Be very careful with switching throttle bodies and intakes. Some throttle bodies have different values during acceleration and the ECM tables won't match. This will cause major issues. Also the intakes will also change airflow, so be warned.