What's a couple of guys with a couple of new code readers to do on a free weekend? That answer should be obvious. It's just too bad both Editor Bob and myself (Associate Editor "Bats") had check-engine lights showing up on our Vettes-his '00 C5 and my '87 C4. Editor Bob had recently acquired a the Granatelli/DiabloSport Predator Corvette Tuner, which we used in the Jan. '04 article, "C5 Retirement Party." The Predator does a lot more than read and clear codes, however. It also functions as a tuner, and it stores your original configuration inside of itself for later uploading.
My C4, having the older OBD I (On Board Diagnostic One) code standard, as opposed to the newer OBD II that the later C4s and C5s use, needed something slightly different. For that, I turned to the EZ-Link by Auto Xray. Mid America Motorworks keeps these units in stock, and ordering one is just a mere phone call away. However, what good is "just a code reader" on a C4 when the ol' paperclip trick still works? The selling point for me was the Scan and Monitor mode. With the engine running, using the Scan program, the computer relays the current OBD information into your handheld device for later use. The Monitor mode is similar, except that you take a short drive while it's "watching" your Vette. This gives you a reading on the engine while it's at speed to gauge usage on several levels that an idle would not indicate. Had I run this deeper scan months ago, I might have predicted the fuel pump problems I had-or even the failing MAF Burnoff Relay, which, as we discovered, was the reason for my check-engine light. So, without further ado, here's how we cracked the codes!