Fuzzhead1506

Figured I’d make this post and update as things go along in case it may help someone else, or if anyone else has had the same issue and cares to add their input.

Car: 2017 c7 z06
Mileage when issue started: ~16,00 miles
Current mileage: ~18,000 (1,000 on new motor)

So Far:
Step 1: Car started blinking the CEL intermittently and going off shortly after when cruising on highway going 60-80mph in 5th or 6th gear. I recall it happened once accelerating from about 50 in 3rd or 4th gear. I checked the OBD port and it was a p0300. I took the car to a dealer 3 times, they replaced the water pump and some pulleys and belts the first trip. The second trip they said bad gas. The third trip they replaced a couple of injectors. P0300 not gone. I was fed up with their waste of my time, so I went to a corvette shop.

Step 2: took the car to the performance shop and they found scoring on the cam, the lifters were going bad and decided to replace the block and associated gaskets to be safe. Clutch also replaced. All fluids replaced. New battery. Received car back, drove it like a grandma for 500 miles, and brought it in for an oil change. $23-24k later (extended warranty covered $14k, only paid for the block itself) I thought this was the end of the problem.

Step 3: when braking in the new block, I thought I had seen something on the dash out of the corner of my eye but never actually caught the CEL flashing. Well yesterday on my way home from work, there it was, the CEL. Got home and it was a P0300 .

Step 4: just dropped the car off at a different dealership that supposedly has a great corvette tech because I cannot afford to spend more on this car and the extended warranty should cover their work. I gave the full list of work done to the car to the service manager and informed him of the recent trials and tribulations. Now I wait. I suspect that this is a fuel or torque tube issue, possibly even electrical or sensor issue… I’ve read online of people solving this issue in so many ways, crank sensor, exhaust valve, torque tube, lifters (but I have a new engine), clutch (but I have a new clutch), etc…
I am no mechanic but it seems like the dealership will likely need to start throwing parts at it to fix. All new injectors, torque tube, fuel filter, MAF sensor, crank sensor, idk what else…

any input would be greatly appreciated. Have any of you replaced an entire block and clutch to find that your p0300 did not go away? Should I lose $8-10k of invested money from the engine plus probably another $10k difference of purchase vs sale price to just sell the thing??? It’s an absolutely beautiful spec with a carbon roof, carbon seats, grey color, matte racing stripes, all the aero and spoiler… so sad to see this beautiful car be a turd… not sure what to do…

edit: car also had code U0078 as of late May after looking back at the scans. Also, the most recent scan from early June showed code B1325 but not the U0078 from late May scan. Car is currently at the dealer I dropped it off at in “Step 4”. I don’t think they’ve even looked at the car yet tbh. I’m going to check in tomorrow, I doubt they’ll have anything worthwhile. Currently scheduled to take the car to a good diagnostic guy on June 19th (1 week from now).

Tinkertech

You need a good diagnostic shop not a parts changer.

How will you feel after spending lots of $$$$ just to have a good diagnostic shop tell you the issue was a $50 part all along?

It appears everyone is just firing the parts cannon at your car.

I wish you good luck.

Vetteman Jack

That is getting to be a very expensive problem with your car. Hopefully you can find a good shop that can find the source of the code and get your car back to running like it should without replacing part after part.

Bill Dearborn

Do you know what the Freeze Frame/Failure Records file indicated when the CEL was set? If there was a cylinder misfiring more than the others it could still set the P0300 general misfire code instead of the code for the cylinder itself. The Freeze Frame/Failure Records file might capture an indication of which cylinder was misfiring. For instance here are a couple of the 24 page print out from my car when I was getting P0300 codes:








Bill

Fuzzhead1506

That would be ideal if it was a $50 part! I agree with you, and the shop that diagnosed my engine and replaced it seems good. I will take it back there again if this dealer can’t figure it out under warranty.

Fuzzhead1506

thank you, yes I sure hope so. I’ll keep everyone updated

Fuzzhead1506

@Bill Dearborn This is a good question and I have a mediocre answer for you, no printouts but an answer. When the car was originally at the dealer, they had replaced those injectors #3 and #8.

Apparently replacing the injectors didn’t fix the issue seeing as how the p0300 is still happening… I’m not sure which cylinders are misfiring now as I haven’t heard back from the dealer the car is at now, but I will post when I know. If it is those same cylinders, I wonder what the cause could be seeing as there is a new block, sparks, wires, and new injectors on those cylinders.

I’ll keep you updated when I find out more info.

edit: all cylinders misfiring. Some more than others, but all misfiring

Fuzzhead1506

Update, car is currently at dealer and everyone is starting to think an electrical issue is causing this misfire. Codes B1325 and U0078 have popped up. Seems BCM/ECM related. Or possibly bad ground/connection/wiring issue.

The misfires started happening after my very first dealership visit back in February where they did a new water pump, pulleys, tensioners, and belts as well as a cabin air filter. Since then, the entire block has been replaced along with many other parts and still the p0300 is not gone.

hopefully resolved soon

Tinkertech

I really hate to read threads like this.

Your caught in a vicious circle of parts changers that are just guessing whats wrong and throwing parts at it.

I don't want to sound like a broken record but you definitely need a good diagnostic shop if you can't do it yourself.

There are some good ones around but they might not be close to you. PM Scanner Daner or C5_DIAG or Bill Dearborn or Dcasole there is also a number of other very talented members on this forum, just can't think of all their names at the moment, they should be able to point you in the correct direction.

The shops you are going to will continue to throw parts at it and maybe they will get lucky but at this point I don't think so.

Wish I could be of more help but I only work and diagnos cars issues as a hobby not as a professional.

Good luck and keep us informed.

Fuzzhead1506

Thank you for the advice. I am not capable of fixing/tracking it myself. It looks like ScannerDanner has a “trained technician” directory on his website with a shop 30mins from me called Autobahn Performance here in south Florida, I’ll give them a call.

Ill keep everyone updated

C5 Diag

Mario Rojas is the Tech you want to see. Tell him to do a YouTube video on this one !!

Fuzzhead1506

[QUOTE=C5 Diag;1607892702]Mario Rojas is the Tech you want to see. Tell him to do a YouTube video on this one !!

Ok that’s great, it seems like he works out of that Autobahn Performance shop down in Oakland Park, FL. I’ll be sure to setup some time with him as soon as I get the car back from the dealer (assuming the dealer doesn’t figure it out).

I really appreciate everyone’s suggestions here, I wasn’t sure where to go with the car but now I have some hope of this car getting fixed!!!

C5 Diag

[QUOTE=Fuzzhead1506;1607892977]
The dealer WON’T be able to figure this out so just get the car out of there ASAP !!....THEY WILL JUST REPLACE PARTS !!!

C5 Diag

I just checked for any TSB's and don't see anything related...the B1325 is a "low voltage to a module or sensor" less than 9 volts or more than 16 volts...the U0078 is a communication issue on the Low Speed Data Bus...modules on this bus are things like Radio, IPC, Telematics so none of these modules if having low voltage would cause a misfire...BCM is on the High and Low Speed Lan and the LIN Bus so that wouldn't be it...the ECM is on the High Speed LAN and Powertrain Expansion Bus so that wouldn't be it either...these may just be 2 unrelated things....I would treat it as such.

Fuzzhead1506

Thank you for that information. I was hoping that may have been an indication of an electrical issue causing the misfire. Regardless, I will make sure to get it over to Mario.

Sadly, south Florida seems to be flooding currently so I am hesitant to go pickup the car and drive 40 mins down the road to that shop considering how low these cars. I’ll make sure to get that ball rolling as soon as I can.

C5 Diag

Yes, a lot of rain here on the Gulf side yesterday and today…I’m sure Mario can figure it out…he’s pretty sharp !!… I’d never bring a car to a dealer for a diagnosis such as yours…another good shop north of you in Melbourne…Assured Auto and Brin Kline is the owner.

Fuzzhead1506

Good to know, you’ve been a godsend. I’ve got Mario scheduled for the 19th, next week. They told me they have about a foot of water on the street outside of their shop and expect to get lots of flooded cars tomorrow, so probably best not until next week… now the last piece of this short-term florida flooding puzzle is getting my car from the dealer back to my house so hopefully it clears up enough for me to get it back this week!!! 😬

I’ll keep everyone updated. I do still have a hunch that it is an electrical issue as it’s bizarre that the misfire would start happening the day after my first dealer visit in February when the did the water pump, pulleys, belts, and tensioners, and cabin air filter. Seems likely they unplugged, pinched, or screwed up a wire (just a feeling) especially considering the replacement of everything.

I’ll try to post a list of everything replaced up to this point

C5 Diag

The only think we can do on this Forum is GUESS but having someone with the knowledge and the advanced equipment like a labscope and other equipment is what you need to solve this…Mario checks all of those boxes.

Fuzzhead1506

In case anyone is curious - here is the list of work done so far… diagnostic scheduled for June 19, 2024. Will update when this is figured out.


Dealer Visit #1 (p0300 started the day after this)


Dealer Visit #2


Dealer Visit #3


“Corvette Shop” Visit (these 3 are all the same visit)

“Corvette Shop” Visit (these 3 are all the same visit)

“Corvette Shop” Visit (these 3 are all the same visit)

C5 Diag

Holy Crap !!...I don't believe a dealership recommended you use an octane booster !!...they (MTBE's) can damage O2 sensors and your cats...what idiots !!...I believe there is a TSB that states not to use these products....octane boosters don't clear out carbon deposits and with your GDI injectors there is a special service they do for this or you can put Techron or other special cleaners in your gas tank.... also they said they found a "weak signal" on #3 and 8 injector ???...you need a labscope to see this and dealerships don't use one...maybe 1 in a hundred or more do...dealerships should NOT have to swap around parts...I NEVER swap parts like this for misfires !!...if they have equipment like a labscope you don't have to guess... I looked again at some TSB's and this one may be relevant...do you have ANYTHING plugged into the DLC (where your scan tool hooks up to) ??...look at symptoms...mentions B1325 and comm issues.





#13-08-116-001J: Aftermarket ALDL or DLC Interface Devices Causing Multiple Issues - (Apr 29, 2024) Subject: Aftermarket ALDL or DLC Interface Devices Causing Multiple Issues Models: 2025 and Prior GM Passenger Cars and Trucks (including BrightDrop) Attention: This bulletin also applies to any of the above models that may be Export from North America vehicles.This bulletin has been revised to add the 2025 Model Year, BrightDrop Models and second Important statement. Please discard Corporate Bulletin Number 13-08-116-001I.
ConditionImportant: Service agents must comply with all International, Federal, State, Provincial, and/or Local laws applicable to the activities it performs under this bulletin, including but not limited to handling, deploying, preparing, classifying, packaging, marking, labeling, and shipping dangerous goods. In the event of a conflict between the procedures set forth in this bulletin and the laws that apply to your dealership, you must follow those applicable laws.

Important: This technical service bulletin (TSB) can only be completed by BrightDrop dealers or BrightDrop certified repair facilities who have met all BrightDrop specific training, tool, and equipment requirements. Repairs must be performed by a technician who has successfully completed the required training.

Customers may comment on various issues with their vehicle related to high or low speed data bus traffic. These concerns may be widely varied, but some of the known issues are listed below.

The information contained in this bulletin is not meant to single out any one device or symptom, but to provide additional information that may be useful for diagnosing issues that do not have other diagnostic methods to identify the root cause.

Note: This bulletin is being written with a focus on full size truck and full size van along with other fleet vehicles, but could apply to any vehicle.

 

Known Symptoms (not specific to any one device)

• The radio may not shut off after shutting down vehicle.
• Bus or LAN traffic may stay active leading to a discharged vehicle battery.
• Problems reprogramming modules either because of interference or the device will not allow the bus to power down.
• ONSTAR® may lose the ability to provide diagnostic data.
• Various engine and transmission performance issues with SES light set.
• Intermittent driveability issues.
• Reduced power message and codes.
• Stabilitrak® message and codes.
• C0561 stored in the EBCM leading to a traction control issue.
• No high speed LAN communication along with various communication U-codes.
• Transmission may not shift for one key cycle (TCM in default mode).
• Erratic gauge readings or flickering displays.
• SES, MIL or CEL light set and numerous DTC communication codes such as U0100, U0101, U186B and U1862.
• Diesel power-up devices causing no power in 4WD low range.
• Erratic electric power steering boost potentially associated with codes U2109, U2107, U2100, B1325, C0000.
• Battery run down
• Service Tire Pressure Monitoring (TPM) system light illuminated.– Cannot relearn TPM
  
• Specific to Hybrids:
  • Reduced propulsion power message.
  • Service high voltage charging system message.

CauseIf nothing else can be identified as the root cause of the issue after normal diagnostics as found in SI, check for a device plugged into the Assembly Line Diagnostic Link (ALDL) or Data Link Connector (DLC) for tracking and/or maintenance interval scheduling. Monitoring devices, along with other electronic accessories such as aftermarket cruise control, or police speed checking devices (RADAR or LIDAR) may cause one or more of the concerns listed above.

Many of the problems described could be caused by an open connection on the HSCAN bus. Example: if the device only makes connection with one CAN +, then it will cause bus errors and erratic ECU behavior.

These devices may be removed by the customer for use in another vehicle while theirs is brought in for service. The intent of this bulletin is to identify a potential source of concerns that do not have other diagnostic methods to identify them. The examples below illustrate some of the devices encountered.

Examples:

The monitoring device examples are not specific to any one design, and styles will vary.
Device W/Secondary DLC Connector