GaryDoug

The Corvette also has the Change Oil indicator. Shouldn't matter for performance, but it explains why you get the DTC 95.

Injuneer

I had checked the code lists for the Corvette LT1 OBD-1 PCM's and there is no DTC 95 shown. The reference is actually "Corvette Fuel Injection & Electronic Engine Management" by Charles Probst, and carries a GM part #. Not to say it's perfect... I found an area where it has the definitions of "open loop" and "closed loop" reversed. So nothing posted below is guaranteed.

The 95 Corvette LT1 PCM is the fabled "OBD-1.5" system, not used in the F-Bodies. The PCM wiring diagrams do not show an active connection for an oil life light. The reference indicates the 94/95 LT1 PCM can be read by an OBD-2 scanner. However, the codes include both the OBD-1 2-digit codes, and the OBD-2 Pxxxx format codes. The OBD-1 codes include those for the oil temp sensor, fuel pump low voltage (although the fuel pump related pin is the A7 fuel pump relay control), and engine oil temp (although I don't see a sensor in the diagrams).

The OBD-2 codes seem to overlap the OBD-1 codes, particularly in the fuel and air metering system range (P0116 - P0175). There is an additional OBD code for the Cat efficiency (P0420) since the OBD-1.5 system added one after-cat O2 sensor. Also includes the GM specific fuel and air metering codes within the range of P1114-P1158.

Somehow, I would be somewhat concerned whether the application we are discussing actually uses an 1995 Corvette PCM.

GaryDoug

I don't remember where I found the DTC 95 explanation while writing the app. But here is one possible place:
GM 95 5.7L VIN P ? OBD/OBD2 Trouble Codes

And you may remember this instance before:
https://www.camaroz28.com/forums/com...f-help-358072/

The oil life light on the 95 Y-car is connected to the CCM, so there's no connection to the pcm there.

I see that the Change Oil indicator connects to the pcm directly on the Impala, but unfortunately the diagram I see only shows the pin number (16) and not the connector number (A, B, C, or D). Pin 16 on the same connector (D), as the MIL lamp (pin D9) on an F-car, is unused. I also see that the oil level sensor for the Impala is on pin D27, which on the F-car is an unused analog input that is sometimes used for the wide-band O2 sensor modifications. Maybe I will play around with D16 and see If I can set a DTC 95 ;-)

dandick

When I run the scan program, under vehicle info it gives me the following VIN:
1G1YY22P5S5117573. I found the GM VIN decoder on the web and it indicates it is a 1995 Corvette. I assume the scan program interrogates the PCM and the PCM provides the VIN info. Is the VIN hard coded into the PCM, or is it something that can be altered?


Please note this is the "new" PCM, but my symptoms are the same, so I don't think the PCM is the problem. The "old/original" PCM was from a 1994 Z28.


I am trying to learn as much as I can about OBD 1, 1.5 and 2 diagnostics and computer controls, but I am much more comfortable around points and carburetors. I think I am going to re-test the coil, ICM and wires, although it doesn't "seem" like that is the problem. The car starts and then seems to flood and load up with fuel. If it was spark related, I wouldn't think it would do that.


I will post the results of my re-testing.


Thanks.


Dan

GaryDoug

The VIN can be changed easily, but I don't think changing the VIN would change anything in the way the engine runs.