You could have an alternator issue.

Could have a bad diode in it causing 'hash or noise' on the +12 line. A noisy power line will cause all kinds of problems. Been there done that with a 'new' rebuilt OEM alternator.

Only real way to check it is with a scope which I did and saw the noise, replaced alternator and issue was solved.

Good luck and keep us informed as to what you find.

 

UPDATE:

I called the local dealership service department to find out if they changed the differential fluid, they didn't, I told the manager about other C7 owners having the same Service Rear Axle message who changed the fluid which cleared the message. The service manager seemed convinced that the differential fluid is not related to triggering that message. I told him that I load tested the battery, I checked the voltage level while driving my car, which shows a steady voltage of 14.5, I also asked if they tested the alternator, NOPE!

Here's my question ... has anyone here had the Service Rear Axle message and after changing the differential fluid, the message cleared?

Thank you for your help in advance!

 

I seriously doubt its the diff service / fluid etc...

I believe your issue lies in the electrical section. You have too many red flags pointing in that direction.

The battery, after the top charge is removed, sitting over night, should read ~12.6 volts with everything off, EVERYTHING, all electronics timed out also. Just leave the trunk open and the light will time out in ~ 15 minutes.

Now connect your meter, a good one.

When cranking the engine the voltage on a 'good' battery should never fall below 10.5 volts, if it does the battery is weak and Corvettes electronics really starts to act up at that point and all bets are off. At this point, cranking, the voltage drops down suddenly and the electronics start to have issues.

After reading your post I'd still try the AutoZone method. That would be a very good starting point in your case.

Cheap and nothing to loose.

 

Thanks very much!

So far I've used my battery load tester with the following results... Engine OFF 12.5 volts, Under a Load 10.5 volts, reading the display inside my car it shows 8 volts with engine OFF, engine running and driving, I see a steady 14.5 volts. I don't understand why there's such a big difference between what I see using the battery load tester, 12.5 volts engine off, and what the display shows 8 volts engine off? I purchased this battery approx 2 years ago, when I leave it undriven for a while, I use a trickle-charger to help keep the battery conditioned.

What do you suggest?

 

Followed your expert advice, disconnected all battery cables, nothing connected to the car, my battery tester/load tester reads 12.3 volts & 10.5 volts under a load. It can't do any harm to stop by the local Autozone for another check. will do.

 

With these readings I believe your right on the knife edge of pass / fail as far as the modules in the car are concerned. Remember, there is some hysteresis in all electronics modules as far as setting a fault.

12.3 volts is basically a discharged battery. Your 10.5 volt reading is dependent on how much of a load your tester is applying to the battery its state of charge before the test. Cheap load testers rarely apply a heavy enough load, or current drain, to tell you much.

I would trust a good conductance tester before using a load tester of unknown quality.

 

Thanks again for the great help!

I took my car to AutoZone, their test revealed that the battery voltage, starter and alternator are fine, it might be time to consider the ELSD differential module?

 

The indicators and gauges in the car are directionally correct at best. Changing the diff fluid will not resolve your problem. The tests that Autozone runs have an error rate that exceeds the requirements of a C7 Corvette, meaning that when they test your battery it may show as good when in reality the voltage is lower than required for your Corvette electronics to function properly. Your readings and indicators are all those of a “bad” battery meaning one that will start the car and allow it to run, but maintains a voltage level below the reference voltage required by your car. You have a bad battery.

 

Never meant to say AutoZone was the best way to go but if thats all you got then thats it, if you don't own any good test equip and know how to troubleshoot it yourself.

You could try a new battery, parts cannon, but........

I test everything to death before I replace anything and at that point I'm almost 100% sure thats the problem. But then again, I have a lot of test equip and am good at troubleshooting.

You have a strange case, confusing readings. Can't really understand the difference in the voltage readings between your tester and the DIC.

Are you sure the small black wire, sense wire on the battery, is in good condition and properly attached?

Is your car completely stock?

I believe something is 'glitching' when you start the car giving you a DTC. (WAG).

If you had a scope you could do a freeze frame on the +12 volt line at the battery terminals and on the output side of all the battery diodes and look for issues. Same on the alternator output, look for noise, drop outs, spikes etc...

If you have a really good DVM (Fluke) that reads in mV on the AC scale, you might be able to see if there is excessive noise, but it would have to be extreme.

Everything points to an electrical problem.

One last 'Hail Mary' is to check and retighten all your grounds that you can easily get to. Note: There is a hidden ground, main neg cable, just forward and on the left side of the battery under the carpet, often overlooked.

Do the easy stuff first, not just in the order that I wrote.

Other than that and shooting the parts cannon, its dealership time.

 

Service rear axle I guess only shows if you have the ELSD?

 

If the EDSL module or any components associated with it were bad you would get a code
As said before , the service rear axle message is a result of another failure in the system 98 % of the time .

The ECM shuts down this and other modules depending on what the failure is . If it is really bad you would see service anti-lock and reduced power warnings also

It's a real pain to find this one .... , it could be just a glitch , did you reset the code ? Has it come back ?

If not , don't worry about it

IF yes can you get a good scanner on the car as soon as the message pops up ? It has to be a scanner that can access all the modules in the car ( cheaper scanners cannot ) You need to look for any codes , present and in history, as this will lead you down the correct path

It could have been an intermittent misfire.... , a bad connection on another module that is on the same communication bus or a dirty ground connection, and as you know, Corvettes are very voltage sensitive...
I am of the opinion that the OEM battery , at 550 CCA is way to small . I replaced mine with a 920 AMP 760 CCA Diehard and said goodbye to putting my car on the charger if it should sit for a week or two . It is now over 5 years old and I still have the utmost in confidence in it as my voltage meter jumps to 14.1 after start and quickly returns to 12.8 after a few miles

Battery load tests are to inconsistent, the only way to get a true picture of the state of your battery is to
1- Slow charge it overnight.
2- Then read voltage with a good multimeter, the reading should be
12 .7 - 12.8 just off the charger
3 - Disconnect the battery from the car and leave it disconnected
4- 24 to 36 hours later , Read the voltage again .....the reading should be no lower than 12.6, if it is, then it's not the battery
5- If it is lower, what is the reading ....?
6- Take another reading the next day and see if voltage continues to drop , if it does , you have your answer
Report you findings here so we can help

Shooting the parts cannon can get expensive and still not solve your issue

Dave

 

Thanks for your response, much appreciated!
I've taken ny C7 the local dealer twice, they replaced the battery connectors after detecting an intermittent drop in voltage, they also found a small amount of corrosion on 2 wire harness connectors at the rear of the car. I was told that the battery tests didn't show any issues. To the best of my ability I checked the voltage using a voltage meter and a battery tester/load tester. I went to AutoZone just to find out if what my test results showed were inaccurate. While the battery voltage display reads 8 volts ENGINE OFF, it reads 14.5 ENGINE RUNNING, is that below the voltage required? I don't have any problem buying a new battery this one is approx 2 years old, I don't drive the car a lot, 2-3 times a month, it's on a trickle charger when it sits a while.

Thanks again!

 

My C7 is not stock, A&A blower, CNC ported heads, BTR stage II SC cam, 92MM TB, LT4 injectors and pump, but I've seen other posts about this issue with cars in stock condition as well.This issues started over 2 years after the engine mods were done.

 

Since your reporting 8v on the DIC and 12.3 volts, all readings engine off, at the battery, you might just have a bad module feeding the DIC or the DIC itself.

I sincerely hope not.

Good scanner time or dealer.

 

Low voltage on the DIC with the key just in accessory or run position but not started is normal .

Dave

 

Thanks, didn't know that !

 

I don't care how "new" the battery is (to the retail buyer), I've gotten two bad brand-new ones from the store the last few years and had to return them. Cars' battery lives are currently all over the ballpark for what seem identical products in like cars. So, as many have said, a replacement is not a bad idea, with the other noted considerations taken into account while doing so. All the best.

 

I told you the likely solution in post 5. Tinkertech mentioned the same concern. I just fixed the same problem on my own car. This is usually a ground issue, and almost always the little black wire. It gets broken internally due to flexing every time the negative battery terminal is removed. Its a poor design. On my car it looked and tested fine but after cutting it back and *soldering* on a new wire end my service Rear Axle message is gone. The system needs a solid ground. I'm not the only one who has had this failure. Its not a particularly easy wire to replace because its down in the battery well but it can be done.

There are two ground bolts you can check on the frame to the left of the engine. If either of those are loose you will get similar errors. I'm not expecting that is your problem but you can check them easily. Open the hood they are easily visible just put a wrench on them to be sure they are tight.

If the battery passes a load test and starts the vehicle reliably there is nothing wrong with it. You can talk about the dealership technician throwing the parts cannon at a vehicle but repeated replacing a battery that passes a load test is the same thing.

 

I'm still don't undestand this.

I can see a small drop in DIC reading when in ACC mode but a 4 to 4.5 voltage disparity from the battery to the DIC? The voltage readings taken at the battery and then at the DIC should be very close. Something is not right.

If this is the case, I would not trust the DIC reading, give me a good Fluke.

 

Problems like this can sometimes come from bad ground connections in the car's electrical system. Since you saw some corrosion on the wire harness clips, I'd suggest checking all the ground connections near the rear axle and chassis. Make sure they're clean, tight, and not corroded.