Injuneer

Was that with the engine running? You have to start it up and watch the volts. It's going to up the voltage to replace the battery charge lost on starting. That's when you will typically see the highest volts, maybe up to 16V.

What PCM and wiring harness are you using for the L99?

lt1cruzin

Yes with it running, at idle. And the harness im using was the one that was originally on the motor in the Caprice. I need to find a second person so i can watch volts at start up.

Injuneer

You don't have to watch the volts as you try to start the engine. Start it up and then watch the volts as quickly as you can get to the front of the car. Or you can watch the dash volt meter.

lt1cruzin

Dash volts never get over 15 or so. Never have trusted stock volts gauge anyway. I have a digi multimeter. When cold first start up of the day, at alt, volts never get over 15.

Guest47904

First I want to throw out to you that the codes look suspicious. At least for LT1's any way. There is no code 54.

So either what you wrote is wrong or the L99 has different codes than the LT1.

Next code issue. If the codes were the same, and you reported a 42. The engine would not run. That means the IC (on an LT1) circuit is grounded. When the PCM for an LT1 has a grounded IC circuit, it shuts off the injectors.

Another code issue. An LT1 will not set a code 55 if a 44 or 45 are present. You listed all 3 of those.

If we don't go any further, I would say that your issues are do to differences with the L99 system that do NOT apply to the LT1.

I suggest you find a forum that deals only with that engine and PCM. I could be wrong. For example the scanner you are using could have communication errors and it is miss interpreting the data. IDK for sure.

My other inclination is that at least some of the wiring is not connected.

If we assume for the moment that some of the codes are the same. Then an open circuit would explain the codes 14 (ECT low voltage), 43 (KS circuit), 63 (bank 2 O2 open circuit) and 75 (trans voltage low).

With KOEO use the scanner to read the coolant temp. Is it reading over 284*F? Then look at the PCM connections. Are there 4 connectors each with 32 pins in this arrangement? http://shbox.com/1/1995_pcm_conn_tn.jpg

You could then check to see if for example the ECT is connected to the White connector of the PCM on the yellow wire at pin 25. The black wire carrying ground to the ECT is connected to the black PCM connector on pin 6. With that wire disconnected, pin 6 should be at ground potential. Code 14 for an LT1 indicates the ECT voltage is low indicating a high temp.

I highly suspect that your PCM is at least wired differently if not entirely different pin configurations. But then your problem could be you have the PCM from one unit and the wiring from another unit.

But then the DTC 51 shows up. That is usually not a good sign.

Hope that helps (at least a little).

I did find these:

http://z9.invisionfree.com/The_Caprice_forum/index.php?

http://www.impalaforums.com/chevy-ca...r-the-l99.html
To a lesser degree these guys
http://ls1tech.com/forums/lt1-lt4-mo...questions.html

lt1cruzin

Thanks! I definitely will check into all that. Wont have time till tomorrow. I did fix the CTS code. Loose pins at sensor. I will also check the ECU plug placement, but w not think it would run at all if plug in the wrong place. Thanks for all the help so far guys! Wont be long now.its been running good since the CTS was fixed. Just rich and no power.

lt1cruzin

Been watching the volts at the factory gauge at start up when cold. It gets between the middle and two thirds mark, then slowly goes down to middle. Too high?

lt1cruzin

One more thing,i just tryed a known working ECU. Same result. SES light comes on as soon as i start it. And i noticed the battery looks like it has been "boiling over". Has battery acid all over the top. So i need to start figuring out whats causing the over voltage. And again it drives fine,just no power and running rich cause of limp mode.

shoebox

Ever have the alt tested? Is the PCM still complaining with a DTC that the voltage is too high? If so, it seems evident where you need to focus.

lt1cruzin

Batt and alt both were tested out of car. What seams impossible is the SAME 12 codes pop up with new ecu. How is that even possible? The battery actually tested too low of volts but never have had a problem starting. I may see if they will just warrenty alt and use a different battery just to test.

Guest47904

All your codes are suspect. I wouldn't believe any of them. That was the point I was making before.

lt1cruzin

Thats what im thinking also, just have to figure out why.

Guest47904

Why don't you force a code to see if your scanner will detect it?

lt1cruzin

Will do. Im trying to see if i can borrow a friends data cable and i already have Freescan from years ago when i had my own cable.

Injuneer

But then there's this from the factory manual, as posted on page 1:

That's the point I was trying to make.