MPRZ

Hey, you may remember me. I'm the guy that embarked on a gearbox swap like two years ago but life kept getting in the way as it often tends to. I'm very pleased to report that the swap is now 99.9% complete, though I did run into an electrical gremlin of sorts. With the gearbox in neutral and clutch pedal depressed, the starter does not engage. Multimeter reads 12.6V across the battery terminals and voltage does not dip at all when the key is turned to the start position - no solenoid click, nothing. The only splice I made in the harness was to change the backup light connector which is different between the manual and automatic. Everything else is intact and connected securely; including the clutch safety switch*.

Could this be an issue with the ECM? I have yet to swap it with one from a manual car, though I wouldn't think this would prevent starting the engine. The wiring diagram shows that the circuits for the clutch safety switch and the park/neutral position switch both terminate to the same pin on the ECM (see attached images). I'll try to test for continuity on the clutch safety switch tonight, but the temperature in my garage right now feels to be around 120F.





*(For anyone wondering, the harness already has the clutch safety switch connector present even in the automatic variants. It is a pigtail that is taped up under the dash at the cowl. It even has a little plastic clip to secure it to one of the mounting bolts in order to keep it away from moving parts. I was pleasantly surprised to find it, as it saved me a good deal of splicing and soldering.)

MPRZ

Oh, jeeze - I totally forgot to add a detail that may or may not be of importance. The car is equipped with a Viper aftermarket alarm system that features remote start. Could this be the issue? I didn't even think of it even though the module was staring me in the face the whole time I was working under the dash.

Edit: The more I think about this, the more I'm convinced that the alarm system's remote start is the culprit. I would ultimately like to disable this feature (dumb to have on a standard transmission), but it's going to take some serious research on my part as wiring is definitely not one of my strengths. If anyone with a better understanding of this can offer suggestions in the meantime, I would very much appreciate it.

MileHightC

Almost guarantee it's the remote start causing the issues...especially given that you now have a manual transmission in there. Have you been able to find any of the install or wiring diagrams for your version of the Viper alarm's remote start feature? I'd start there and see what you need to do to uninstall it.

Worst case, you end-up spending some cash with a local audio/alarm company to do the uninstall of see if the guys will do 'side work' for cash as it would save you on the shop rate.

MPRZ

Thanks. Yeah, the model is a Viper 5701, and a PDF of the wiring diagram was easily obtained online. If I can't get it sorted myself, I'll do what you suggested and try to get someone out to assist. It's kind of a bummer, because I was really excited to get the whip back on the road!

DannoXYZ

Start wire to ECU is only input that tells it key is set to start. Key also sends
signal to starter-solenoid. As you suspect, alarm is intercepting signal between ig-switch and starter solenoid. For troubleshooting:

1. using small alligator jumper, connect +pos power from solenoid input terminal to small +pos activation terminal on solenoid. Does starter run?

2. Bypass starter-activation on alarm.

3. Ultimate for-sure 100% test is to measure voltage leaving ig-switch start wire. Trace it all way to starter-solenoid and measure at junction. Where power disappears tells you problem is between that junction and previous one that did have power. Simple.

MPRZ

Okay, so after struggling with this immensely I bit the bullet and took it in to the nearest shop. I'm taking the L on this one. I'm a little peeved because when I asked what the guy did to get it started, he started the whole "I don't speak English too well" thing. Anyway, water under the bridge. The box runs once again. It's actually running quite well, and the gamble I took on a pick-and-pull transmission paid off. It goes through all the gears and shifting is buttery smooth.

My question now - how can I go about programming the VIN to the new (manual) ECU? All of the diagnostic tools I'm seeing online that have writeback capability are well out of my price range. Is there a way to do this with a laptop and OBDII adapter?