I took my car to get all of the fluids replaced a couple of months ago (45k mile maintenance in the book) and since shortly after that I've been having weird and increasingly more pervasive electrical issues. It started with a rare seeming reboot of the gauge cluster where the LCD screen would blank out and come back with the corvette logo and the gauges would do the 0 to full sweep when you turn on the car. Occasionally a service rear axle issue would pop up after it did that. I made an appointment to take the car back in after it happened but an early snow stopped me and I haven't had time since due to the dealer's high unavailability. As of Thursday night the passenger seat won't always move backwards or tilt backwards and the HVAC fan blower has stopped working. The dealer said that when they were removing the exhaust to replace some of the fluids they had not disconnected one of the O2 sensors and pulled the connector pins out which caused me to have to drive some stupid truck of theirs for a weekend while they ordered the wrong part and then finally got it repaired. Is there a single harness that could have been compromised when they did that or when they replaced the exhaust? If not, does someone have an idea as to where to start looking before I take it in and waste a bunch of time and money?

 

The o2 wiring wouldn’t have anything to do with those type of issues. I’m not sure what they could have touched to create that kind of problem unless a ground somewhere was compromised. Removing exhaust shouldn’t require touching any grounds.

 

Weird stuff happens with computers in vehicles. I had a aircraft that all 5 displays where showing a large red X fail upon landing. After many hours of troubleshooting it was a bare wire on a anti ice valve # 2 engine. Which no one thought should have anything to do with the problem. But sure enough it did, it was causing a issue with the flight computers. Now I never disregard what could cause a issue. If you take something apart and a problem comes up right after that 99% of the time it is something you did, going in there.

 

Not sure what year your car is or how old the battery is but if it's 3 years old or older I'd replace the battery first. My battery in my 15 failed the 3rd year and strange stuff happened,

 

When the battery in my 2014 started going bad I saw several gremlins pop up.

 

My car is 3 years old, so I'll go get a new battery and see if that fixes it. Thanks for your suggestions.

 

My '15 Z06 is doing the exact same thing - service rear axle and dash zeroing out and the video blanking out multiple times. I just dropped off at the dealer. Did the battery fix it?

 

It did not and the dealer couldn’t replicate the issue. If anything it has gotten worse, but I haven’t had time to drop it off at the dealer again as it is my only car and since spending nearly $1000 for them to flail around and then replace the heater blower motor I’m reluctant to bring it back to them since all of the problem are still there.

I have found that if it is getting in a loop of doing it over and over again that I can brake hard or sometimes accelerate hard and it stops. The colder the weather seems to exacerbate it. My other engineering coworkers agree with me that it seems to be a harness or connector issue, but I still haven’t found a good diagram of all of the wiring harnesses of the C7. It could be something as simple as a wire in a harness going to ground when it gets rattled in the right position, or it could be as difficult to find as a connector that has some internal breakage. I have a deep suspicion of the CANBus on the vehicle as Chevrolet doesn’t use differential signaling and settle for using single wire and power ground.

 

Does the dealer have the same mechanic working on the car each time you take it in? It makes it more difficult if the people working on the job have some feel for what was done before. I take it the shop dropped the exhaust to bleed the clutch as I don't know any other fluid service that requires dropping the exhaust. With the O2 sensor damage being the way they described (pins pulled out of a connector) there was significant force that could also put pressure on the harness that takes the O2 sensor wires to the ECM. It sort of sounds like they need to backtrack along that harness to see what else might have happened.

The left side O2 sensors get their +12 V power feed through engine harness J117 which goes through the plastic harness channel that runs along the back side of the engine and to the underhood electrical center. Tied to that same junction are power feeds for the Valve Lifter Manifold Assembly, Engine Oil Pressure Control Solenoid Valve, Evaporative Emission Purge Valve and the Supercharger Bypass Valve Solenoid (if you have a Z06).

The fight side O2 sensors get their +12 V power feed through engine harness J115 which also goes through the plastic harness channel that runs along the back side of the engine to the underhood electrical center. Tied to that same junction are the power feeds for the vehicle speed sensor and the Multifunction Intake Air Sensor.

The manuals don't show a clear path for the output wires of the O2 sensors to get to the ECM Connector X2. One set of diagrams show them ending in 4 connectors located at the rear of the engine but nothing showing what those connectors connect to to take the signals to the ECM. The view of the rear engine harness channel show 4 unidentified small connectors that might be the ones that connect to the sensors. The ECM connectors aren't identified in this view but it looks all 3 of them are at the end of the harness that comes out of the right side of the harness channel.

I imagine the interactive electronic manuals the GM shop has will provide better break out since you can hyperlink to other sections while the paper manual leaves you scratching your head wondering where does this go.

Bill

 

I explained exactly what you said when I took it in as they did the work (well not the specific connectors and harnesses), and they said, "Oh that wouldn't cause anything". I was pretty angry that they pulled the pins out when they dropped the exhaust to change/bleed the clutch. I think they really just want to charge me as much as they can for my car since it is out of the bumper to bumper warranty and they figure a corvette owner will pay whatever and is willing to do without their car for however long in the winter. I don't know where else to take it as I don't take cars to Autonation and the other chevy dealers aside from this one are pretty far away and I don't know who to take this car to.

 

It might be worth having a discussion with the dealership service manager (not service writer/adviser). Explain everything was working fine until one of his fine employees dropped the exhaust without disconnecting the O2 sensors thus causing damage to the connectors and maybe to an upstream wiring harness due to the weight applied and what wires pulled on what other wires.

It could be the wires caused the engine end of the exhaust to hit something when it was dropped.

Bill

 

Side Q: What fluid change needs the exhaust to be dropped?????

Maybe when the exhaust was hanging by the Ox sensor wires, it put so much strain on the wire-harness, above where the first harness clamp is, that the metal edge of the clamp cut through some of the wire insulation.
I would follow the ox sensor wire harness to where the first retention clamp is (probably on the back of the cylinder heads), and carefully inspect where the wires pass through the clamp. Also, the ground bolts should be checked, pulling on the wire may have loosened them. Also, check the tightness of the +12V (caution these are 12V battery hot all the time) connection nuts that are between the underhood fuse box, and the coolant reservoir. There are 3 or 4 studs/nuts under 2 black plastic covers, in this area.

From the engine removal thread:
We also need to disconnect two 13MM ground bolts connected to the back of the cylinder heads (one on each side and shown with yellow arrows below) as well as two 15MM bolts used to bolt the large wiring harness to the back of the heads (one on each side shown with red arrows below). These two 15MM bolts proved to be the biggest pain in the *** out of the entire job so far, so best of luck with those. Simply put, they serve no mechanical purpose and are just used to secure the harness from moving though the harness cannot move much anyway in that area. That being said, I will NOT be reinstalling these! For Simplicity, I am showing a pic of where these bolts are after the motor is already out so you can see them better.

 

The GM CAN bus is differential signaling, 2 wires, plus a ground/shield wire. All CAN buses use a 2-wire differential signal wire configurations, as defined by the CAN bus interface specification/standard.

 

I had a similar issue and run in with the gauge cluster sweeping and blanking out, service rear axle notifications as well as a weird exhaust pulse which cleared up at increased throttle. my particular issue began when I changed the battery, I don't think had all connectors flush. I would have to believe if at the dealer for service, they may have disconnected the battery during service of the vehicle. I took my car into to the dealer and they had it for two days and did not find a thing. Not saying I know the fix, but here is what I did.

1. put the vehicle in Touring mode under performance setting and set the screen up to see voltage / Alternator charging state. (this will help you determine if your voltage is spiking when things go haywire with your gauges) your voltage should fluctuate in controlled stages but should not spike up and down quickly)

2.if your battery voltage is spiking, like others have mention, you want to check all ground connections. I would suggest starting at the battery leads. (in my case there was a bent eye connector on one of the smaller wires of the main neg cable. this connector was touching the metal of my main neg cable terminal connector and once bent straight the car now runs without issue.

3. if the battery positive connections are not completely flat against the metal connections (metal L bracket) I believe this caused my initial issues as it was my first battery change on the vette and learned my lesson on how any minor changes in operating voltage can create issues.

4. if the battery ground and pos connections are good, check all spark plug wires and connections to starter/alternator. some have posted these connection can create similar symptoms

I hope your issue is the same as mine in terms of the simplicity of the fix, but I solved my issue by starting where changes to my vehicle were made, hence where the problem began. I

I will be buying a tech2 soon, because I know first hand it sucks when your beautiful Vette is sick..... and I hate taking my Vette to the dealer. best of luck OP.

 

My car is still being diagnosed. They did a reflash under a TSB, checked all ground straps as well as module grounding internally and externally. Suspicion is now around the alternator. They can see voltage jumping up and down, up to 16+ volts. They are also getting guidance from an external engineer.

 

Got my car back (jeez I missed it - exactly one month in the shop). Final duagnosis/fix was to replace the alternator.

 

Still no issues since the new alternator? My car is doing the screen thing. New battery, all terminals checked, all grounds checked. I was already leaning to voltage changes maybe causing the issue.