hgh pwr

I purchased a used pcm for my 94 and my car still will not start ,so i was wondering if i ground 4 and 12 on my diagnostic port will it tell me if its bad?

93Rubie

Probably not. It may or may not throw codes but codes do not necessarily mean it is bad. Does the car crank ok? What tests have you done?

hgh pwr

well I have the ltcc on my car and my car quit running several times going home from work and when I removed the cover from the ltcc to see the led's, it has a green and a red and when there is a problem the red flashes a code which was 4 flashes and the instructions say no est signal from pcm.

I contacted bob bailey and he confirmed that my pcm was bad,so I purchased a used one from a company that sells them on e-bay,
It looked like it came from the Titanic,so I cleaned it up and put it in and installed my custom program with tunercat and still will not even think about firing off,it turns over fine and gets fuel but no spark.

i guess i will take it to my local chevy dealer and see if they can test it to see if its good,but I think its a piece of you know what.

Plus anyone interested in buying the ltcc should think twice in my opinion,have had more problems with it than 3 optisparks,has left me stranded more than once.

I also don't take any pleasure in bashing any product that is for an lt1 and bob bailey is a great electrical engineer but his product needs some improvements to be more reliable.

93Rubie

I'm not really familiar with the LTCC system but if it is using the EST signal from the PCM, how is it getting this? Is it spliced in? Did you verify that that signal is being received at the LTCC unit?

Don't be surprised if a GM dealer does not even want to test your PCM much less work on your Corvette, regardless of the fact it has an aftermarket ignition. Most of the folks working there would not know what the heck an LT1 engine was. Unless, you happen to run into an older mechanic that has been around GM for a while and is knowledgeable on them.

hgh pwr

Yes its spliced in and what the ltcc does is it lets you run an ls style coil setup,which consists of 8 ls1,ls2 coils.
The system works well,but in my case there is really not a good place on a vette to install it where it doesn't get wet,heat or vibration causing it to not work and leave you stranded.
I am removing the ltcc and going back to the stock setup.
Bob bailey who designed and built the conversion said it would be difficult to get a signal with a volt meter,the signal pulses.
Firebirds and camaro's are better suited for the ltcc because ther is a lot more room to install it.
Well i plan on taking it in to the local dealer and see if they can test it,they still work on older vettes and i am sure they heard of an lt1.

Hooked on Vettes

You can pull PCM codes by shorting Pin 4 to Pin 12 on the
diagnostic connector. Turn the ignition ON and they will be
displayed on the Dash Cluster LCD. Module 4 is the PCM.

The PCM will set code 41 if the Ignition Control signal is above
4.6 volts and engine rpm is below 1500.

It does NOT light the Service Engine Soon Indicator.

DTC 42 will set if the PCM detects 84 crankshaft revolutions
with out any activity on the Ignition Control circuit. That is the
White wire circuit 423, from the PCM pin B5 (shown as Pin A12
in the diagram posted) to Pin B of the factory Ignition Coil
connector.

It does NOT light the Service Engine Soon Indicator.

To check the signal.

You disconnect the LTCC plug that plugged into the factory White
wire at Pin B of the factory Ignition Coil Module connector.

With a Volt meter set to AC, you measure the White wire that
goes back to the PCM Pin B5. Voltage should be between 1 and 4
volts AC when you crank the engine. If the test is good the
the LTCC module needs to be tested.

93Rubie

You should definitely be able to test and see if you are getting signal from the ECM to the LTCC module with a voltmeter.