1983 Chev G30 motor home 2012 LSI with transmission drive

[Russ C]

This has been 3 years in the making. Purchased 2012 6.0 L96 VORTEC ENGINE AND 6L90E 6 SPEED AUTOMATIC TRANSMISSION. ECM, TCM, & FCM all stock, harness stock all from the donor vehicle, going into a 1983 G30 Chev chassis motor home. My back ground is 40 years in design and servicing avionics.

I need some help with the above. All components are mounted and wired. Instrumentation is Dakota Digital (very good products). Harness 100% beeped out. HP tuner is talking to everything, so buss is active and appears to be working. Where I am is the following.

I cannot get the starter to work. If I take the ECM out of the circuit (unplug both connectors) and apply A+ (battery voltage) to connector J1-52 wired to the buffer starter relay (200 ma coil) the engine will turn over, so that appears to be OK.
I have disabled VATS so I think that is off the table. I have monitored J1 pin 1 of the ECM and get a low (.2 volts or statically .02 ohms to ground) when transmission is in either park or neutral so that is off the table.
Being a EE I have followed solid engineering principals in the wiring department, so I am pretty sure that is off the table. Although at my age the only thing that is for sure is nothing is for sure.

I do have a GM 2012 wiring manual for the exact vehicle (2012 Chev Express 2500) and have eliminated the BCM. However, I may of missed something in that direction. I don't know if the ECM has a problem. J1-52 of the ECM looks like (according to my drawing) a PNP transistor (a drafting teaser) that is ties to pin 52 of J1.

So, if anyone can help, I would appreciate it.

[dave w]

:welcome:

LT1 Swap has good wiring information, http://www.lt1swap.com/E38%20ECM%20Connector%20Pinouts.htm but has not updated to 2012.

Are you using the 6L90E Park Switch circuitry to the ECM? Are you using the ECM to control the Starter Relay circuitry?

LT1 Swap information is very helpful for engine transplants, but typically bypasses Park Switches and Starter Relays.

dave w

[Russ C]

Thanks Dave...
I am using the signal (park/neutral pin 3 trans. connector ) from the transmission wired to J1-1 (ECM) I am new to this form so hopefully missteps forgiven...

I think I am expecting a little to much from the OEM design, and have made some assumptions that are not valid. I will attempt to attach a drawing that reflects where I am today. 14859
I will rethink the start circuit and change to a more conventional design.

[dave w]

Perhaps using the J1-1 signal directly to the starter relay will work? What I'm thinking is the J1-1 wire will provide a ground signal when the 6L90E is in Park or Neutral. The starter relay can be wired so the engine starter circuit will only work when J1-1 is ground.

dave w

[Russ C]

Perhaps using the J1-1 signal directly to the starter relay will work? What I'm thinking is the J1-1 wire will provide a ground signal when the 6L90E is in Park or Neutral. The starter relay can be wired so the engine starter circuit will only work when J1-1 is ground.

dave w

Well, that signal is only good for something less than 100 ma. (.1 amp) most auto relays are 200 ma coils. A simple PNP transistor with the base circuit limiter draws less that 2 ma (.002 amps). This has solved the start problem. see attachment

Russ C

[dave w]

I'm curious where the TCM P/N switch current rating is published?

I'm curious what current is needed for the HELLA H41773001 Solid State Ceramic 32 Amp SPST Mini Relay?

I really like the PNP transistor solution posted above.:thumbsup:

I really like using off-the-shelf automotive parts when working with automotive applications.

dave w

[Russ C]

I'm curious where the TCM P/N switch current rating is published?

I'm curious what current is needed for the HELLA H41773001 Solid State Ceramic 32 Amp SPST Mini Relay?

I really like the PNP transistor solution posted above.:thumbsup:

I really like using off-the-shelf automotive parts when working with automotive applications.

dave w

Dave:

I have attach where I found the spec on the max current from the TCM.

Russ