I don't know about the "OBD 1.5" term, but otherwise you are correct. The 94 and 95 LT1's have the 16-pin port and have both OBD I and OBD II code structures. IIRC, the 94 and 95 LT5 do not have OBD II codes. I also know that the dash cluster diagnostics don't support the LT5 either.

OBD II was mandated to be fully implemented for model year 1996 by the Feds. For some reason,  the 94 and 95 Corvette have pieces of both. Yes, there are OBD II codes in the 94 and 95, but not nearly as many as the 96 has. Basically, the OBD I codes are duplicated by their respective "P" code counterpart in OBD II, but the operating system is OBD I based.

OBD II for real begins in 1996 on Corvette. The 94 and 95 are OBD I.


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So, on a 94 or 95, there will be all OBD1 codes available and only some OBD2 codes?  Is that correct?  To pull the codes, the pin-out would be different, since the 16 pin connector is used, but basically you could still short the proper pins for that connector to get the OBD1 codes?  And, with proper software, you could get both OBD1 as well as limited OBD2 codes?  

One of the major componets of OBD II are the "drive cycle monitors". These monitors are set after certain paramaters are met by actually driving the car. There are also post-cat converter sensors that monitor catylist degradation during the life of the vehichle. If catylist performance deteriorates below certain thresholds, a code is set. Evaporation controls and monitoring are specified for OBD II. (Many people are aware of the CEL coming on for forgetting the gas cap. This is part of OBD II).  The way History and Active DTC's are logged and retrieved are part of the OBD II spec.

The above are all specified to be included in OBD II. None of them are included in the 94-95 Corvette. Because the 94-95 is OBD I.

Yes. Only the corresponding OBD II codes to the OBD I system are available.

Yes. You can retrieve the OBD I codes via the CEL just like the 85 using a "paperclip".
Yes. Tthe pinouts are different.

The really cool feature of the 95 is the ability to use the speedo readout and the trip / fuel buttons to query and retrieve the diagnostic codes for ECM, BCM, TCS, ABS, and Suspension (called "modules"). You can also cycle / monitor the inputs / outputs for the BCM. The onboard diagnostics in the 95, using the speedo as the display are very powerful and useful. Teach yourself more about them.

Dave, thank you for the tip on the added features of the 95.  I will research more about how to use them.  They seem very, very useful and sound easy to use since they utilize some dash buttons and the speedometer display.

|UPDATED|6/18/2013 9:21:33 AM (AZT)|/UPDATED|