Basic Diagnostics YOU CAN DO IT!

[Ccmano]

Anyone who has been around our ZR-1’s long enough understands that on these ~30 year old cars if something hasn’t already gone wrong, something will eventually. When that day comes we have two options. 1 try and fix it yourself. 2 Pay someone else to fix it. Given the lack of competent LT5 specific repairs shops around the country, the likelihood is that many will try to fix it themselves.

The first temptation is to go to places on the internet like this forum or possibly a Facebook group and look for answers. Very often this works well. Many issues are commonly known and their resolution is as well. That’s what makes these groups so good. Dynomites “Solutions” thread is a wonderful example.

However, as many know, there can be multiple issues that can present as a single problem or multiple problems that have a single solution. Human nature being what it is we all look for the quick fix. I’ve been guilty of it myself. Sometimes you get lucky. A certain part is suggested as a fix by several people. You replace it and the issue is resolved. But, sometimes and probably more often, you can throw multiple parts at an issue and still have the problem. All this results in wasted time and money, not to mention frustration, in trying to solve an issue. I’ve seen people sell cars because of this, when it could all have been prevented.

I’ve worked on cars for over 40 years and have been a certified MB tech. I have supervised technicians and worked corporately for 3 manufacturers. If I have learned anything, often by my own errors, it's that time spent doing proper diagnosis saves countless hours, dollars and frustration.

In our case, GM supplied its technicians and subsequently us with a fantastic diagnostic resource in the Factory Service Manuals it published for each model year. In particular for those vehicle systems governed by those early computer systems in the ECM, CCM, BCM and DIS. A high percentage of the issues encountered with our cars can be traced to these aging systems. Luckily for us GM has provided detailed diagnostic trees for most drivability issues and for any of the multitude of codes that these systems can show. While not necessarily pinpointing the problem, these Codes and diagnostic trees can walk you straight to the issue without needless expense in time or money. The caveat is that a certain degree of technical ability is required to follow these trees and reach the correct conclusion.

The purpose of my post here is to urge ZR-1 owners to first buy a copy of the FSM, the LT5 Manual and the Electrical Manual for their year car. Then secondly, if you do have an issue, check the systems for codes and use the diagnostic trees in the manual, along with input from knowledgeable members, to properly diagnose your problem. Don’t get caught in the expensive and frustrating habit of throwing parts at a problem only to find wiring issue. Or, post about a problem, here or elsewhere, and get a dozen different potential solutions from people who “think” they had that issue and such and such fixed it.

We are all here to help make ZR-1 ownership a positive and rewarding experience. But you do need to help yourself so some degree. Get at least some of the tools to do that. The Manuals noted above and a good code reader, preferably a Tech1, the factory diagnostic tool. They are regularly available on eBay for $250 - $500. You likely paid tens of thousands of your Z. Don’t skimp on the basic tools.

Hoping your Z ownership experience is a positive one.
H

[TX '90 ZR1]

THANKS for posting this!!
Very sage advice!!

[32valvZ]

Luckily I havent had a code issue up to now. I have an MT2500 Snap On scanner. Would I be better off selling it and buying a Tech 1?

[Ccmano]

Originally Posted by 32valvZ

Luckily I havent had a code issue up to now. I have an MT2500 Snap On scanner. Would I be better off selling it and buying a Tech 1?

As you can see other OBD1 scanners work to a large degree. I like the ability to know that what is being described in the manual is exactly what is see on my Tech1 and as noted some things can only be done on a Tech1, 1a or Tech2.
H

[Ccmano]

I don’t want to give the wrong impression here. With some of these diagnostics it’s not just a simple matter of plugging in the scanner and “bang” there’s the answer. In addition to scanner readings many of these diagnostics require voltage, ohm and continuity testing of the wiring harness, modules, relays and switches. That takes a good automotive volt/ohm meter, some know how and practice. This is where help from fellow members come in. To some this will be daunting. You’ll know pretty quickly if your cut out for this or if it’s time to hand it off to a professional. The point being your not wasting time and money throwing parts at it and going further down the road to frustration.
H

[Paul Workman]

Originally Posted by Ccmano

I don’t want to give the wrong impression here. With some of these diagnostics it’s not just a simple matter of plugging in the scanner and “bang” there’s the answer. In addition to scanner readings many of these diagnostics require voltage, ohm and continuity testing of the wiring harness, modules, relays and switches. That takes a good automotive volt/ohm meter, some know how and practice. This is where help from fellow members come in. To some this will be daunting. You’ll know pretty quickly if your cut out for this or if it’s time to hand it off to a professional. The point being your not wasting time and money throwing parts at it and going further down the road to frustration.
H

Couldn't agree more, Hans!

[Paul Workman]

Originally Posted by 32valvZ

Luckily I havent had a code issue up to now. I have an MT2500 Snap On scanner. Would I be better off selling it and buying a Tech 1?

Somewhere I think I still have a MT2500 stashed, but for lack of the proper modules it is collecting dust. What modules for the MT2500 do you use for the ZR-1, and are they still available do you know?

[32valvZ]

Originally Posted by Paul Workman

Somewhere I think I still have a MT2500 stashed, but for lack of the proper modules it is collecting dust. What modules for the MT2500 do you use for the ZR-1, and are they still available do you know?

It came with the purchase of the car. Honestly, Ive never even turned it on.... I havent had any issues (knock on wood) regarding codes.

[We Gone]

Great post I also have a very nice scanner Genisys EVO 5.0 that I can use on many cars from OBDI up to 2011 of different makes and models. for some diagnostics on our cars can only be done with a tech 1.

[rush91]

When I bought my Z, thankfully all manuals were included. They have saved me countless $ by reading and following the step by step instructions GM layed out 30 years ago. A MUST for all LT5 owners.....