We need info about the car, specifically the year. There are a number of differences from year-to-year in the scanning requirements. 93 can be scanned with a paper clip. 94 takes an OBD-1 scanner with 12-pin cable, 95 is OBD-1 with 16-pin, 96/97 are OBD-2.

If you have spark, you have a low resolution pulse to the ECM/PCM. How did you determine you have no injector pulse? Does the fuel pump prime for two seconds when you turn the key to “RUN”, then shut off? Does the pump restart when the starter is cranking the engine? In order for that to happen, the ECM/PCM needs to see the low resolution signal from the Opti and the fuel enable signal from the PASS-Key II (VATS) system.

 

Sorry about I forgot to tell you it's a 94 camaro lt1 in a ratrod. I'm just his neighbor. I know and understand how the sensors and computer works together. Well before we changed the opti we used a noid light and had no pulse.we have twelve volts to injectors. Vats has been shut off in table. I did that in tunercat. When it was running he took it out and when it shifted it back fired and died and it would keep doing that from what I was told. Well he has no fuel gauge and he swore it had plenty of gas and it didn't. But then he did somevwelding on the cab and he thinks it might have fried the computer. Well we replaced it with acjunk yard pcm and removed vats. But we were looking at the voltages of the opti and we did have spark. I used DVm to check voltages and we had the grid, 12v, 5, 1.2 volts we unplug the the connector and it went up to five volts. I watched the GM video on the opti so understand the concepts. He putbthe new opti in from jegs but says no go I'm not sure if you can put a 94 opti in out of time. I read you can but a obd1 scanner for 150-200$. I'm just checking voltages because that what I have to work with. I been over all the computer grounds too and they are good. Is there something I can look at in the bin file.

 

You can download free scanning software specifically for the 93-95 LT1, written by a member here. Can show/log all sensors, PCM parameters and reports DTC's, reads ABS, air bags, two way communication to actuate devices and clear codes.

https://www.camaroz28.com/forums/com...95-lt1-874306/

There are often sales on Actron OBD-1/OBD-2 scanners for $100 or less. Avoid Equus and Innova scanners. They have a corrupt database for the LT1 and return false results.



It is very possible to index the splined Opti driveshaft incorrectly to the cam sprocket. About 10% of the installs seem to fail that way. There is no way to determine from scanner readings that the timing is incorrect.

 

Appreciate your help. I'm seeing him today. I'll keep you updated!

 

Downloaded that app you suggested. I still need t find a read me file. To understand what's going on. I do have a screen shot for you. Don't know how to attach a file in this forum No DTC but looks kinda weird on somethings.

 



 

I don't know if you got the picture I'm struggling to use editor

 

What sort of info are you looking for in a "read me"?

There are some things "odd" because the engine isn't running, and some things "odd" because it appears devices are not hooked up:

- RPM shows as 45 when engine is not running

- target idle speed shows as 3188 when engine is not running

-- IAC counts show high because the PCM parked it there so there would be adequate air flow into the engine when it started cranking

- Coolant temp at -40-degF typically indicates an open circuit on the coolant temp sensor in the water pump housing. DTC 15 will set when the engine starts

- TPS volts only reach that high when the throttle blades are wide open. Or maybe the TPS sensor is not connected, wired incorrectly, or faulty. 100% TP is derived by the PCM based on voltage. DTC 21 will set when the engine starts.

- MAP = Barometric pressure, because the engine is not running

- O2 sensor readings are normal for cold sensors. They show the bias voltage applied by the PCM

- Fuel trims are defaulted to 128, because its in Cell0, and closed loop is not enabled

- The "0" and "1" in the last column indicate whether a system is enabled or off. The only odd one is Power Enrichment, but the PCM had probably set that because the TPS is at 100%

- DTC 43C is not covered in the factory service manual, but indicates the knock sensor circuit is open. If you started the engine, DTC 43 would set.


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Well are brains are hurting right now. But I wanted to tackle the tps and ect because they are out of wack. But I tested the ect sensor and got about 250 ohms. That's not open . then with key on I'm getting close to five volts even on the ground. So we pull connector of ecm and and check to look for some voltage. B-6 is tied to tps and ect but grounded at transmission. So checking for continuity to ground at pcm connector. And shows a good ground. What puzzles me is how I can get voltage out of a sensor ground when everything is hooked up. And I am probing both pins of wire going to ect. I got look at tips and find out why it has such high voltage too. I'm figuring it's coming from pcm. My buddy wants to add a ground to the pcm plug but it's got a ground to transmission.any way that's were we are at.

 

4th Gen LT1 F-body Tech Articles

What are you measuring the ground against when you are getting 5 volts? With or without the harness connector on the sensor.

I didn’t say the “open” was necessarily in the sensor itself.

 

No open means any where. I understand that. I believe we had the meter on body ground a then probed the two pins. I would expect 5 volts on yellow wire and nothing on ground. The same ground is used for TPS. Might the reason the TPS is showing WOT. I was wondering how access the shoebox articles. I was looking for the ECT resistance values and you mentioned shoebox to some one. We're wondering what difference between a sensor ground and the pcm ground that is external to the pcm the grounds that are grounded at front of block. If we can figure out what's going on with the ect and TPS I'll move to the knock sensor. I'll keep checking all grounds.

 

Not clear if the connector was on the sensor or not. Connector off the sensor, key on, do you have 5 volts across the two connector pins (yellow / black)? Per the Shoebox procedure. Ditto with the gray / black wires on the TPS. The PCM supplies regulated 5 volt reference to insure accuracy of the sensor voltage readings. With the PCM ECT sensor a 2-wire circuit is provided because the PCM needs a very accurate temp reading. With the sensor in the head for the dash gauge, they use a 1-wire circuit, relying on the engine/chassis ground, Minor variations in voltage are not critical to the limited resolution of the gauge. You need to keep the reference ground from the PCM.

B6 does not pick up the ground at the tranny. It SUPPLIES the reference ground to the fluid temp sensor in the tranny.

If you have 5 volts on any black wire in the ECT / TPS / TFT circuits, there’s a short in the system, or the PCM regulated voltage is shorted internally.

 

Good news is -it's running but without a TPS(new item internally shorted I assume). We changed back to original pcm. Same problem. I decided well maybe it's internal short on atf temp sensor so we pulled big plug on tranny . So I hook up ect and TPS and tried to start for a second check ECt again approximately 4 volts on both wires. What the hell. So I disconnected TPS and it started. Running at fast idle. But running. We replaced that TPS because it didn't have a smooth resistance sweep. But when I got the new one I checked the resistance and it was nothing near the other values. My gut feeling was why is it different but it's new and didn't realize the engines can run without one. I'm now wiping a lot egg off my face. But thanks to you letting me know about the tune app. That was the first chance to see any numbers and values. I'm hoping it will cure the high idle. It actually ran with the bad TPS but sometimes it would start and not others. Does any one know off hand what the actual resistance is from grd pin and the 5volt referenced pin on TPS. I want to check it before we in stall it. I appreciate your patience inrealize you don't know who we are and how knowledgeable we are. I sure know a hell of a lot more than I did before I started this journey. I'm hoping my buddy did too!

 

The PCM elevates the idle speed on cold start, based on coolant temperature. There's a table in my scanner writeup showing stock programming target idle speed vs. coolant temp. Scroll down to page 5 for the chart.

https://www.camaroz28.com/forums/com...-guide-886891/

Note that at a coolant temp of -40°F the PCM sets the idle speed at 1,200 RPM.

 

Great thanks a lot ! I'll check that out ! I want to check our knock sensor too! I'll see how far I can get from here.