lt1cruzin

Just bought some one else s headache. But got it real cheap. 94 v6 with a 94 l99 swap.Very clean car. But im trying to get it out of limp mode. Scanned it with my friends expensive scanner and got these twelve codes. 58,14,45,44,43,42,55,54,53,51,75,63. Has a brand new alternator and AC Delco 02s. Possible bad grounds? Has a Borla cat back. Thats the only mod that i know of.

lt1cruzin

Went ahead and bought another ECU. For the price I got it for I can sell one or the other f for a core and make my money back. Weather wont be good enough till Monday to tear into it. I want to check all grounds first before i swap it.

RamAir95TA

You should know that it will be VERY difficult for us to help you with your problem. Don't expect much response because we will know even less than you will especially when dealing with a frankenstein swap.

I can tell you this though - the PCM itself is hardly EVER at fault. Ever.

shoebox

I would first clear all codes, operate the car, scan again.

lt1cruzin

Codes have been cleared a few times. Same 12 come up. Its not a Frankenstein car. Its like any other lt1/L99 swap. Yes im using the L99 prom. I keep getting a bad prom code along with all the others. I did find the ECU main ground wasn't tight. Didn't help much after i fixed that. I am going through all grounds before i put this one in. One thing, i did have to replace the alt right after the swap. Wonder if that had anything to do with it. Doubt it though. After the battery is unhooked all night,or i clear them with scanner, SES light comes on very quickly and i get those same codes.

lt1cruzin

And I know lol its a pain when dealing with swaps. I do appreciate what help I can get though.

Injuneer

DTC 53 indicates the PCM has recorded excessive charging system voltage on the power supply to the PCM. The code sets when the voltage exceeds 17.1V. The shop manual indicates when this happens, it shuts down all device outputs to protect the control system components, and when that happens it may result in a lot of codes being set because of the shutdown, not because of problems.

As usual, Rob/Shoebox has given you the answer.

lt1cruzin

Battery was dissconected all night last night. As soon as i started it ses light came on. Scanned it. Same 12 codes came up. I cleared codes the day i.got it. And a few times scince. Still...same codes. New alt. I may swap batterys. Check again.

lt1cruzin

I have been doing what he says. Same results. Thats the first thing i did.

kevhogaz

As Injuneer said, your alternator is exceeding 17.1 volts, and shutting down every sensor that would be fried by such high voltage.

You need to check your alternators output voltage, and that would be your starting point. If it's over 17 volts, it's bad. It should be right around 14 volts.

lt1cruzin

Thanks! I just replaced the alt with a new rebuilt unit when i first got car, but will take it out have it tested this weekend. Gotta love Duralast parts lol.

parkers Z28

Check the volts at the pcm .. maybe something got crossed up during the transplant ?????

Injuneer

You need to check the volts. No need to pull the alternator until you have done that.

lt1cruzin

Will do! Thanks all for the help!

lt1cruzin

14.57 at alt 14 .45 or so at battery.