ZR-1 Maintenance Tips

General Maintenance

by Jim VanDorn


The most common call we receive by far is from a confused ZR1 owner. After years of reading everything from which thermostat to use, to what type of spark plug is best, the average owner is totally and completely confused...and for good reason. There are many varied opinions of what is best for our cars but that may depend greatly on how you use your ZR1.


After seven years plus, many ZR1's are finally accruing some mileage. We have had the opportunity to closely inspect many engines with a variety of types of use from normal street driving to severe "weekend" use (track time). Compiling this information we can now offer the ZR1 owner some observations. One rule we've adopted after hearing so many owners say the same thing is the "DIMWIT" or "Darn, if I didn't Mess With IT" rule. In other words, if you didn't have a problem, then what are your intentions in the first place? To date, the only company known to have a fleet of engineering ZR1's to test with was GM and it's affiliates.


Therefore, we must ask ourselves if their suggested procedures and parts recommendations should have a considerable amount of merit. Obviously they do, but on the other hand, there are no doubt areas for improvement. Although we will begin our segment discussing the routine and normal maintenance of the ZR1, there are many areas where an upgrade will be suggested.


Please understand that these are personal opinions and experiences and are not intended to conflict with service procedures outlined in the appropriate service manual.


Thanks to Erle, Hib, Ed, James, and even Bruce, I've figured out how to read Diagnostic Trouble Codes on the 1994-95 MY ZR-1.


The 1994 service manual is confusing on this issue. It says you cannot read the codes on cars with the 16 pin connector under the dashboard right above the pedals. The reason for this is because the 94-95 LT1 cars were wired up for OBD II, which was required in 1996. Since the LT5 was going to be discontinued after MY1995, there was no OBD II implemented on the LT5, but it got the 16 pin connector anyway.


I was able to read the codes on my 94 ZR-1 by grounding the #6 pin by connecting it to the #5 pin. If you look at the connector, it is trapezoidal in shape. The wide part is the top, the narrow part the bottom. The pin on the top left is #1, the top right is #8.



It's simple enough to use an unfolded paper clip to make the connection. Having done the above, turn the ignition key to the "on" position, but do not start the engine. Every relay on the car comes on (except the fuel pumps), so don't be alarmed if you've never done this. The "Service Engine Soon" light will flash a code 12 three times. It will flash once, then pause, then flash twice, then a long pause, then repeats two more times. Code 12 indicates everything is working. After the code 12 flashes three times, the SES light will flash out any DTCs that have been set three times each, starting with the highest numerically. If the SES flashes four times, then pauses, then flashes five times, then it's DTC 45. Follow the service manual for diagnosis and corrective action. Disclaimer: I provide the above information to save any 94-95 owners some time figuring out how to read DTCs on their ZR-1s. Use the information at your own risk. If you're not comfortable with that, please take your car to a qualified technician.

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