C4 Corvette Performance Verification

[Colton S.]

Re: C4 Corvette Performance Verification

TL;DR: For 1988, YES.


GREAT question! You're paying attention to details.

Beginning in 1986, C4 have 2 "Security Systems" The Universal Theft Deterrent (UTD) and the Vehicle Anti Theft System (VATS). Many people misunderstand the function and segregation of the two systems, and tend to combine malfunctions they don't understand into "Must be VATS".

The 1986-1989 VATS is a stand-alone system. If VATS does not detect the proper key resistance value upon power-up, it inhibits cranking, and does not send the Fuel Enable (FE) signal to the ECM. There is no indication to the driver that VATS is causing the starter inhibit (no crank). You should know that Code 46 in the ECM is only present when there is an active VATS inhibit. (Code 46 means "No FE signal present"). If your car doesn't crank, check the codes, if you see 46, you know why. VATS is not checked during a PV.

The 1986-1989 UTD does not inhibit cranking like it does in 84-85 and again in 90-96. So your 88 should crank and start with the horn honking after a UTD trigger. If you have any trouble with this in Florida, have Tom call me. He may expect the 88 to behave the way a 90-96 does, but it doesn't. He'll listen to me. :grin:.

Basically, in 86-89 VATS protects the car against drive-away theft. The UTD protects the contents. 90-96, a triggered UTD also inhibits cranking and FE. (I bring this up in case a 'helpful' individual misunderstands how your 88 is supposed to function.)

You're doing great.

10-4, thanks so much for your info, your a great help.

[Ed H.]

Re: C4 Corvette Performance Verification

No Colton he just likes to type, but he does know his stuff and it's raining so he can't play with his fiberglass duckies. One of the good guys.

[Colton S.]

Re: C4 Corvette Performance Verification

Hope you don't mind if I ask another question. The front turn signals alternate, my question is do they always alternate or only at "night" when the parking lights/headlight switch is pulled? Thanks again.

[Colton S.]

Re: C4 Corvette Performance Verification

No Colton he just likes to type, but he does know his stuff and it's raining so he can't play with his fiberglass duckies. One of the good guys.

lol, he does know his stuff.

[Terry M.]

Re: C4 Corvette Performance Verification

The front amber side marker only flashes "alternate" when the park/tail lights are also on. Here's why:

The side marker bulb's two wires are one to the front turn signal circuit and one to the tail light circuit. (Neither side of the bulb is directly to ground.)
> If turn signal is ON, the side marker bulb grounds through all the park/tail bulbs to ground, and is ON.
> If the park/tail lights are ON, the side marker bulb grounds through the turn signal bulb filament to ground, and is ON.
> If both the park/tail and turn signal are ON, there is B+ voltage at both sides of the side marker bulb, and is OFF.

So when the park/tail are on, the side marker is on. When the turn signal comes on, the side marker goes off. Hence the "alternate", but park/tail has to be on for alternate.

I know how to touch type, and I use a laptop with a real keyboard for my posting. It is easy for me to get carried away and type too much. Sorry.

Dave

A historical note. That alternate flashing of the turn signal/side marker began in 1972. I never understood how they did that. Thanks for your explanation.

[Kevin G.]

Re: C4 Corvette Performance Verification

Bring along a calm mindset! Much easier said than done....

A person's anxiety and adrenaline can run high, while attempting pre-PV upon arrival to the meet. Take your time when unloading the vehicle, if it's trailered. There have been some folks that, mistakes caused personal injured and or damages to the cars, not thinking before acting. A "tip" to your thread.

[Floyd B.]

Re: C4 Corvette Performance Verification

Dave,

>> VATS is not checked during a PV.

Does this mean that if an owner installs one of those VATS bypass thingies available on fleabay, the car could still pass PV?

Thanx

[John M.]

Re: C4 Corvette Performance Verification

Colton, John Marsico here. Dave Peery and I judged your mechanical section in Frisco. I am happy to see you are moving forward with your car.
I want to mention 2 instances regarding light blubs. In May, 2021 we had a C5 turn signal light that was working Intermittently and could have been a major PV problem. Fortunately for the owner it worked that one time, but did not later. The second situation occurred when I did my PV. The owner after me was going through the static test and his right rear side marker light did not come on. The C4 team leader gave him his 15 minute fix. I was standing near watching the process. I told the owner I had a bag of spare bulbs in my car and I would go get a fresh one for him. During the time it took me to get to my cay and back to his, he told me he didn't need the new bulb, he jiggled the old bulb and it was working fine. The team leader returned, the owner went back to the marker lights and you know what's coming, it didn't work, Of course he failed and went home. Bulbs are not that expensive, I would bring along some extras just in case. Good luck with your PV.

[Floyd B.]

Re: C4 Corvette Performance Verification

Yeah, good point - I suppose there's a 100 ways to cheat on a PV and all I did was pluck a single example. But then, what's the point? To boost the price of the car on the auction block with a phony PV certificate or gain the satisfaction that you presented a car that operates as new?

[Colton S.]

Re: C4 Corvette Performance Verification

Colton, John Marsico here. Dave Peery and I judged your mechanical section in Frisco. I am happy to see you are moving forward with your car.
I want to mention 2 instances regarding light blubs. In May, 2021 we had a C5 turn signal light that was working Intermittently and could have been a major PV problem. Fortunately for the owner it worked that one time, but did not later. The second situation occurred when I did my PV. The owner after me was going through the static test and his right rear side marker light did not come on. The C4 team leader gave him his 15 minute fix. I was standing near watching the process. I told the owner I had a bag of spare bulbs in my car and I would go get a fresh one for him. During the time it took me to get to my cay and back to his, he told me he didn't need the new bulb, he jiggled the old bulb and it was working fine. The team leader returned, the owner went back to the marker lights and you know what's coming, it didn't work, Of course he failed and went home. Bulbs are not that expensive, I would bring along some extras just in case. Good luck with your PV.

Thanks for the advise.

[Colton S.]

Re: C4 Corvette Performance Verification

The front amber side marker only flashes "alternate" when the park/tail lights are also on. Here's why:

The side marker bulb's two wires are one to the front turn signal circuit and one to the tail light circuit. (Neither side of the bulb is directly to ground.)
> If turn signal is ON, the side marker bulb grounds through all the park/tail bulbs to ground, and is ON.
> If the park/tail lights are ON, the side marker bulb grounds through the turn signal bulb filament to ground, and is ON.
> If both the park/tail and turn signal are ON, there is B+ voltage at both sides of the side marker bulb, and is OFF.

So when the park/tail are on, the side marker is on. When the turn signal comes on, the side marker goes off. Hence the "alternate", but park/tail has to be on for alternate.

I know how to touch type, and I use a laptop with a real keyboard for my posting. It is easy for me to get carried away and type too much. Sorry.

Thanks for your help, I really appreciate it. You are great at explaining things.

[Colton S.]

Re: C4 Corvette Performance Verification

Dave, I've gotta another question for you. What is the normal idle rpm when the transmission is in park. I couldn't find this info in the service manual. Thanks