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Hello LS1Tech - I'm having issues with my LSA swap and hitting some dead ends with my troubleshooting. Hoping someone with more knowledge might be able to point me in the right direction.
Completed an LSA swap back in 2020 and it's been running like a champ for two years without any major issues. Went to a car show in 100 degree weather and had some cooling issues. Went to add an oil cooler and beef up the trans cooler as well. Didn't touch any of the wiring whatsoever and now the LSA won't crank at all. When I turn the key to crank, I'm no longer receiving a 12V signal to the to the starter. Did bridge from the positive terminal to the solenoid and the starter immediately turned over - so no issue there. I plugged in my HP Tuner to check the DTC's and the following came up. Note: LSA Coolant pump is running fine, fuel pumps engaged/ON, and everything seems to be fine. I'm just stuck and self admittedly I just don't have the knowledge to troubleshoot further. Is it something to do with my O2 sensors? I recall I had an issue with the intercooler coolant pump output from the PCM detecting the pump was running and the same issue occrred where it would not send signal to starter. Car was running fine and now it's not. And to throw it wrench in it - trying to take this car to Hot August Nights in Reno next week and then this happens after 2+ years of running great. Any help is appreciated and thank you in advance to the community.
We'll, if you are not getting 12V at the starter solenoid, then that's obviously the problem. Find yourself a wiring diagram. It's going to either be the ignition switch, relay or wiring.
I don't know what vehicle you have, but doubt it's anything related to O2 or anything like that. But the wiring diagram may reveal anything else on that circuit.
Thank you LiljayV10, 01CamaroSSTx, and, strutaeng. I very much appreciate the responses.
The car is a 66 Impala with a OEM wiring harness. The LSA wiring harness is from PSI and those guys were great to work with. The wiring diagram is exactly as noted from PSI - been working and running great for almost 3 years. I double-checked all of the fuses and verified voltage output from the relays (12.7V's). This really has me stumped and I'm wondering if there is anything I can look in the PCM to (HP Tuners - Scanner) that could lead me to a fault of some sort? As you can see in the pic from above, could I be having an issue with an O2 sensor? Does the PCM do some sort of validation and if an O2 is bad, doesn't allow the car to start? I guess I can go down the process of elimination and replace the O2's.
Either way fellas - really appreciate the replies and guidance.
O2's do not cause a no start and you have something going on with the ignition circuit so you need to find out where the interruption of power is that's leading to the starter solenoid. Can you jump the starter off from the starter relay connection?
The PSI harness has the starter wire going directly from the harness to the solenoid. I even called them when I was installing the LSA motor to confirm this was sufficient and I didn't need a relay. They told me to go directly from the harness to the solenoid. I checked that wire and there are not breaks or issues with it, so that's why I'm focusing on the PCM, as the wire is coming direct.
Tranny = Hughes 4L80E and all of the PCI harness is installed.
FIXED! Ended up being a burnt up ground in the harness from the header heat. I wrapped the headers with the DEI titanium product, but my under the hood temps are getting really hot. I had no idea the supercharger would add this much heat. I was also told that my tune may be the issue for the heat - adding too much fuel. I had the car tuned by supposedly the "best" in the bay area, but not 100% I agree with that statement.
Thank you all for leading me down the path of checking all of the wiring - you were 100% correct in your assessment and I can't thank you guys enough. Very much appreciated and now this old guy gets to go to Hot August Nights!
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LSA Swap - No Crank Issues 
