BCM Start signal

Tuned an l26 out of an '05 Grand Prix, it has been transplanted into a different chassis. I had to wire the BCM into it to send the start signal from the BCM to the PCM to get it to run. This isn't VATS, it's litterally the serial data class II signal that the BCM commands the PCM to start with. I've done the re-link, done the 30 minute re-learn, poured over the BCM prints and satisfied all of it's inputs but it's still intermittent at best, only running once in a while. Hopefully somebody has a suggestion to get past this before it becomes a problem for more folks.

Hasn't anybody else transplanted one of these?

What PCM are you using and what vehicle is the motor now in. Currently I would say post your tune so we can see if you missed anything.

The 2005 Impala PCM (different PCM I know) does the same thing. It wants to see the BCM give its ok regardless of what you command the PCM ignore. Ryan (DarthFireo I think) did an LS4 swap into a Fiero using that same PCM you have, and found out it needed a BCM (which was fine for this setup as I think his customer wanted factory remote start and locks, which Ryan integrated into the build, and the BCM controls said functions).

My workaround was to flash a 2003 Grand Prix file to the PCM, which doesn't require a BCM to operate. Had I known that HPT can't actually disable VATS in these PCMs (though they swear up and down they can) I would have gone straight for an '03 GP PCM and saved myself 100 bucks in licensing that I'll never EVER use.

Whoa, sorry I haven't checked back, 2 responses! Well, as far as using a 2003 GP PCM, they switched to the E40 in 2004 when the L36(Series II 3.8L) was phased out and the L26 (Series III 3.8L) was in, so that 2003 PCM is the earlier style. The 5.3L engine must be using the earlier style in 2005. The PCM is service number: 12591278, it's in a Fiero based kit car and using it's 4T65-E tranny. I'm trying to post the tune, here but I don't see where to add it.

Found it, here's the tune, and a pic of the PCM tag, Does anybody know if the 2004 requires the start signal? it's an E40 as well in that year. Thanks in advance.

Not sure if my situation applies, but we installed an 06 grand prix power train with wiring harness and dashboard onto a piece of custom built farm equipment. I wanted to adjust various paramenters in the PCM but the 06 grand prix isn't supported so I have an 05 grand prix PCM installed on it with the 06 BCM. I believe I got it working by setting VATS to none and using "Write VIN/Tunerlock/VATS". Maybe with the BCM in there the PCM still got that "serial data class II signal" that you mentioned earlier. I also managed to get the 06 PCM working in the car that the 05 PCM came from by using the 05 PCM's hpt file and using "Write VIN/Tunerlock/VATS" to disable VATS.

On another note, I have an 05 Lacrosse PCM with the same service number: 12591278.

Is there a benefit to doing the tunerlock? I'll try it but it didn't seem like a good idea at the time. I have the BCM that came from the same car.

This didn't help but I heard there was a break though where it got fixed in the last couple of weeks, can anyone confirm that?

Never did work, lost $100 in HPT credits on a PCM that will never run and switched to a 1997 L36 PCM and a re-pinned L36 harness from a camero.