LT5

Trying to get this thing running the best i can, had a pcm for less tune. Car still has the same 4 codes when i hook her up to the scan tool. 16= low voltage to opti? 24= Vss low signal, speedometer does not work still been trying to fix this. 50 System voltage, 67 Ac presure sensor circuit. The Ac will be entirley removed asap, as for other lights the abs is on and brake light. I will be removing all abs and it has a line lock so im sure thats why i have those to lights on. Also the low oil light is on, which i have no idea why since the oil is new and not low. Any ideas? I reset codes they just come back. The car does not want to start at times then wait a while and fires right up. Then ses light will turn off, only comes back on when i have braked really hard and everything goes low. Car runs alot better when light is off, then when on. I may just have some bad voltage wiring problems, there is rust on battery cables ext that im going to deal with soon. But code 16 bad opti?

Phoenix'97

I am going to throw this out there, is it possible you have a completely deteriorated engine harness and whether it is arcing or a bad ground, it is throwing the PCM out of wack and triggering all these other codes not associated with the Optispark? Someone else posted a thread about where to go for a brand new engine harness for our cars and I found a place that actually makes them brand new and to exact spec for direct-fit and plug-and-play status.

LT5

I think you could be right, because on the tps sensor i can see all three wires showing, on the other sensors like the iac and things the wires bare are visable. I saw a site where they are about 600 dollars and are even a better material then what we use now (bigger i mean) and would bolt right up. I thought this whole time i had a charging issue.

Phoenix'97

I have learned A LOT of things from my Trans Am over the course of my ownership. Some things were my fault but I didn't know better, other things were intentional and by shops I took the car to. When I replaced my engine with a Jasper reman, I opted to have ceramic shorties put on. Well, I regret that move, they ended up melting the wire harness on the passenger side where it plugs into the PCM. The shop that installed the engine and my headers could have wrapped that PCM harness section in heat cloth wrap, which was done years later, but they wanted me to keep coming back for fixes due to "age" of the car. Nope! The wire harness was grounding, arcing, and doing all sorts of things that threw off my gauges, tripped gauge lights, and contributed to the premature failure of a brand new optispark, the only odd-ball that wasn't ruined by oil or coolant contamination!

Over time the wires on our harnesses will get brittle, shrink, and start exposing the wiring or if they happen to break and don't have a good ground, you will have plenty of problems that mimic symptoms of components going when really the wire harness may be the culprit! When I have my finances in order and am ready for the "new car loan" I will make sure I get my engine harness replaced. For next summer, I plan to get my shorties removed and throw on the stock OEM cast-iron exhaust manifolds, perhaps having a place media-blast and ceramic coat them before then! Another interesting thing I found, there is a business that can custom make me new cast iron exhaust manifolds, given iron is relatively dirt cheap. I was wondering if they could fabricate LS style exhaust manifolds for my LT1. That certainly would be something!

LT5

I agree i have 3 wires on the tps that are bare wire, all wires on other sensors like iac are also. I did not notice this till recently. Found a good wiring harness for 560 but i won't have that money for some time. Anyway to just start fixing this one is where im at.

Phoenix'97

Let us know how it goes! There is nothing wrong with a used engine harness if worse comes to worse and you are on a budget!