96 corvette
my sys light came on the other day, I had disconnected the battery to work on the headlight cover , and afterwards is when I stated noticing the sys blinking. May not have anything to do with the timing. I did some research and performed a test with the jumper wire and there were no active codes only H71 and H72. I tried to clear those but they’re still there. I pulled all the fuses and checked them, only the cigar fuse is blown and no matter what I put in it blows the fuse. But either way the sys light remains blinking. I did experience a hesitant start this morning and had to give it a little gas but afterwards idels great , drives great, and the volt sit at 14.7
Any ideas?

 

Could it just be a weak battery?

 

If I remember correctly, the 72 would show if you have an after market radio so that code can't be cleared, but it has no effect on anything mechanical.
The cig lighter fuse blowing would indicate there is a dead short somewhere in the wirling.

 

Do you think that would cause the sys light to flash?

 

It shouldn’t

 

Thanks for the insight. I’ll check the cigar fuse out. Hopefully find a solution to the sys blinking also.

 

The only time I've seen a "system" light is when I had a failing battery

 

Same thing with my 94. Aftermarket radio. Theres a thread here somewhere on how to get the sys light to shut off due to a radio change but it was way over my comprehension..

 

H71 and H72 are associated with the backlighting in the radio and HVAC. This code will show up with an aftermarket radio if the car has C60 Manual A/C controls (which do not have an LCD display.) H72 is not likely to set in a car with C68 controls because there is still the HVAC backlight on the circuit.

The usual 'phantom code' that sets in my 92 and I frequently see reported here is H74 which is associated with the green LEDs above the buttons on the radio, HVAC and fog light switch.

First question: Is the SYS message consistent? Or does it come and go? You are correct that a SYS message is only present with an active, ie a C-code in Module 1, the CCM. Because there are no Current faults, the SYS light should not be on.

I would clear the codes. (Module 1.7, push eng/metric until "- - -" is displayed.) Turn key off, wait a bit, turn key to RUN, "C12" should be displayed. Wait for the SYS message to appear again, and recheck codes. If the SYS message is intermittent, you have H71 and H72 again, and there is an aftermarket radio, I'd try the resistor fix. (I would definitely try the resistor fix if it has aftermarket radio and manual A/C controls, which 3,377 1996 Coupes had.)

There are/were two connectors behind the radio. You're looking for the connector with an orange on one end, pur/wht next to it, and gry/blk next to it. Ie, the 3 wires are on the end. (If the connector has been cut off, go by wire colors.) Wire a 10,000 ohm resistor between the orange and the gry/blk wires, and another 10,000 Ohm resistor between the orange and the pur/wht wires. This should take care of intermittent H71 and H72 and the intermittent SYS message.

EDIT/ADD: For the OP's cig lighter fuse short: This fuse also powers the accy wiring connector at the front of the center console compartment. Orange wire. There is a pigtail that was supplied with the car plugged into the harness, but the 3 wires were just bare and taped off. If the orange wire has become shorted to the black wire, it will blow the fuse. It is also kind of common for the lighter socket to become shorted when aftermarket accessories like a charger cord push the center connector prongs outward and short to the shell. << Conduct a close visual inspection. These are the only items on the Lighter fuse.

 

I will look into all this and update. I expected to see an active code like I mentioned but was more confused when I didn’t. I’m new to the corvette world and trying to learn what I can.

 

Try disconnecting the battery and touch the clamps together to clear the system and reconnect to see if any changes.

 

Ok so I think the negative battery terminal was loose, tightens it up. Still showing sys. Did the paper clip and don’t see a current code. So it’s perfectly safe to disconnect the neg and pos battery terminal and touch the cables together to clear? Just want to make sure, I’m obviously new but it’s better to ask again then be wrong

 

Ok so I think the negative battery terminal was loose, tightens it up. Still showing sys. Did the paper clip and don’t see a current code. So it’s perfectly safe to disconnect the neg and pos battery terminal and touch the cables together to clear? Just want to make sure, I’m obviously new but it’s better to ask again then be wrong

 

What cavities did you put the paper clip in? If you have a SYS message, you have a Current "C" code in Module 1.

You can touch them together. BUT! Disconnecting the battery does NOT clear the CCM codes. ( I wasn't sure, so I went out to my car and tried it in my 92.)

You never answered this question: Is the SYS message constantly displayed? Or is it intermittent? Does it come and go? (The SYS message is ONLY displayed when a fault is currently present. History codes do not illuminate the SYS message.)

This is how you pull and clear codes in the CCM:

Jumper 4 and 12. See sketch below.
Turn key to RUN. Watch the speedometer. There should be a code(s) in Module 1. (Module 1 is the CCM. The SYS message pertains to an active code in the CCM. if you have a SYS message, there should be code(s) in module 1.)
Let all the codes run until "A - - - " is displayed. Write them down including the "H" and the "C". All C will be accompanied by an H. C-codes illuminate the SYS message.

Push TRIP/ODO until "1.7" is displayed.
Push and Hold ENG/MET until "- - -" is displayed.) Turn key off, wait a bit, turn key to RUN, "C12" should be displayed. (C12 in Module 1 means 'Diagnostic Mode, no codes.)

Report back with your results. (If you still have C/H71 and/or C/H72, does your car have C60 Manual HVAC controls AND an aftermarket radio?)

1 -2 - 3 - 4 - 5 - 6 - 7 - 8
9-10-11-12-13-14-15-16

 

The sys message intermittently blinks.
jumped 4 and 12
c71 and c 72
tried clearing it and the ——— pops up all most immediately after hitting the eng/met control
codes won’t clear . Tried it a few times.
i do have a aftermarket radio that was installed by previous owner. I bought this car a couple months ago and maybe it’s been blinking the whole time and I just didn’t catch it. If it’s just a radio code will it hurt to just let it go? Thank y’all for all the advice, this forum/ community is great!

 

Do you have manual HVAC controls? Ie, a slider for temperature? (Electronic controls have a blue and red arrow for setting temperature, and an LCD display for temperature, fan speed, outside temperature.) (Without the "resistor fix" an after market radio and manual A/C = constant SYS message.)

If = YES, purchase some 10,000 Ohm 1/4 or 1/2 watt resistors to have onhand for the next time you have the radio out. The instructions and wire colors for fitting the resistors are in Post #9, 4th paragraph.

The SYS message is a series of 3 flashes every 15 seconds when a Current-code fault is present. What I meant by "intermittent" is that during a drive cycle does the SYS message cease for minutes at a time, or perhaps never appear at all. With two C-codes, you probably have a constant SYS message.

You can let the lighting codes go, they don't affect anything other than the annoying SYS message.

 

Thank you very much for the advice. I understand what you’re asking about, sorry for the confusion. Yeah sometimes when I’m driving it’s goes for a while without blinking, even to the point that I think it went away. But then comes back. So I’ll get the the resistors and do that. I have to trace a problem with the cig lighter, it instantly blows any fuse I put in it, so I might have to pull the radio and cover off to access that wiring. Maybe knock them both out.
Also yeah Manuel HVAC nothing digital about it

 

Read the last paragraph in Post #9. It has some details regarding the lighter fuse blowing.

The resistors will fix your SYS message.

Whew.... Lot of typing.

 

@IHBD Do you know if this would apply to my '90 as well? Every time I plug something into the lighter socket, it blows the darned fuse in the auxillary fuse box under the RH side knee bolster.

So I just don't plug anything into it anymore. Got tired of uninstalling and reinstalling that bolster as it's a pain in the rear end to keep having to do it.

But I would like to resolve the problem.

 

The 90 does not have the accessory connector in the center console.
In a 90, the lighter is on the CTSY fuse in the main fuse center. Not in the AUX fuse block under the RH side. (1991 is first year for the accessory connector, and the lighter fuse moves to the AUX box on the same fuse as the hot at all times circuit in the accessory connector.)

I think that if you were to remove the lighter socket from the console and inspect it closely, you can find what is bent that is shorting when something is plugged into it. Another detail I've learned over the years is to never align the ground contacts on the side of the plug with the (+) contacts in the bottom of the receptacle. They may touch and short. Look down there as you put the plug in and align the side contacts on the plug 90 deg to the contacts in the bottom.

The power door locks are on a fuse in the AUX center. It is pretty easy to pop the fuse when R&R door panels. I put automatic thermal reset breakers in the AUX fuse locations so I don't have to ever access them. In the 92, I do use the accessory connections for my stuff I use on road trips. I occasionally short something out, but all I do is fix the short and resume what I was doing. The breaker resets, I don't have to access the aux fuses, and no wire damage.