I apologize in advance as I know I will be asking for help a lot with this project but that makes me super thankful for this forum.

Just bought a 2017 Z06 A8, the bad news is that it came from copart with a front hit. Radiators, crash bar, steering rack, abs module, front cradle, and a few suspension components are the main areas of damage.

I started tear down today in order to determine if engine was free and thankfully I can put a wrench on the crank and it turns and can feel it come up on compression.

That being said I got battery all charged up and wanted to see if the car would turn over on its own. It will not. Let screen start up and when you press in brake pedal and hit start the main display goes dark except the engine light. All other interior lights remain on. After a few seconds the main screen comes back on. Hooked it up to scan tool and cleared all codes we could, however the scan tool will not connect to the ecm. All fuses are good checked them twice.

Does this car have a low oil level safety switch? The connector on the dry sump looks untouched as well as wires going to the ecm but wondering if it may have been crushed somewhere?

Also would the abs module being completely destroyed and removed be the issue as you need to press brake pedal to start (which we are doing)?

I stopped for the night and will get back at it tomorrow. Just looking for some guidance besides don’t buy a salvage car.

 

If your steering module is damage, it won't complete the DATA circuit to the ecm to allow the engine to start. I believe the EBCM will do the same. If there are any module disconnected or damage, I believe it will need to be sorted out first.

Look at the side rails and front rails for damage as twist or bent.

 

Thanks! The connection on the electric assist motor is destroyed and disconnected and the abs module connection is also destroyed. So this is probably my issue. I just wanted to hear this thing run before I spent a bunch of money fixing systems only to find out it has a knock or worse.

 

After doing a lot more reading it appears I may be in for a difficult time. Since both the brake module and steering rack electronics are destroyed I have no choice to replace them. But from what I’m reading it sounds like the only choice is to purchase new as used ones will be Locked to their old respective cars. Am I interpreting this correctly?

My nearest dealer with a corvette tech is well over 200 miles away. Local dealer is 50 miles away. Car won’t run so getting it back on the trailer will be fun enough as it is.

Any guidance that can be offered would be greatly appreciated and would help stop me from buying a bunch of used parts I can’t even use.

 

I would check your can bus to see if it's open circuit. Especially since you can't connect to the ecm. You can check the can bus from the obd2 port with a meter. I would google it or a service manual. I had the same thing happen and ended up being can wires were broken and the wire looked good.

 

No, new or used you will need an SAE J2534 pass thru device and a subscription to SPS to program the modules to your VIN.

 

If you ABS module is disconnected or the plug is damaged I do not think it will let you start the car please correct me if I’m wrong,

 

Okay I’m investigating what SAE J2534 device I will need and looks like the subscription is only $40 per vin. Sounds like my best hope so far in being able to install used parts.

 

The dealer 50 miles away should be able to reprogram the modules. That doesn't require any special Corvette training. In fact, most maintenance can be performed by people without Corvette specialty training. Look at all of the people who aren't even trained as mechanics that do their own maintenance.

As for the data circuit not being completed it depends on the amount of damage done to the harness and connectors. The EBCM and Power Steering Modules can be removed from the circuit and the engine will still start. Note the Data Communication Circuit in the following picture:

The connectors that connect to the EBCM and the Power Steering Module pass the signal through the connector to the next module in the circuit. If the connector is trashed and the connection through the connector is broken then you will need to repair or replace the connector or maybe the harness.

One other thing can keep the engine from starting is the system is killed after a collision. If the battery still had some charge in it when you got the car and it wasn't disconnected and reconnected the engine won't start. Have had to disconnect/reconnect the battery to get several C7s that were wrecked at the track started so we could drive them home or get them on a trailer.

Bill

 

Thank you, it’s good to know she will at least run with out the steering or abs connected. The battery was dead when I picked it up, it’s sat several times now overnight with battery disconnected and still no crank. The abs connector and steering connector are pretty trashed, some wires are showing copper etc. I will clean that wiring up tomorrow so I at least know nothing is shorted together or broken. If it can’t be fixed I’ll have to look at some harnessing which hopefully appears to be somewhat modular and wouldn’t require an entire new harness. Worse case scenario I may bypass at the starter so I can at least hear her turn over. Hard to order parts for a car you don’t know the engine is okay or it. Roll the dice!

 

Definitely look at all the wires up front and remove plastic loom. I bought my car back in 2015 salvage and same situation. As soon as I new I had an open circuit in the can bus I check all the wiring. The loom wasn't even damaged where the wires were broken. I had to replace the steering rack and abs module. That didn't stop me from starting the car. Good luck with the project!

 

Thanks! I’m replacing the same obviously have yet to track down a reasonable rack. I sent you a pm as well

 

I know it's expensive, but I would recommend this. MongoosePro GM 2
This is what you should expect a professional to use. GM MDI 2

 

Did you check the 300 am fuse that supplies main power to the starter? It's in the back on the top of the battery. That is a 12V high amp 100% on all the time feed to the starter. The ignition triggers a relay on the solenoid that engages the starter.

Also pull the starter off and test it. You can easily do that with 12 volts. If the engine turns over easy then I would start with those two areas. If the 300 am fuse went, I have another thread where I can show you how to fix for dollars compared to hundreds to replace the entire assembly.

 

I actually saw your thread on the fuse. It tests out fine and I know the cable is seated properly as well. I didn’t get anything done today, woke up to -7 degrees and didn’t have the motivation to go down to the shop even with the new heaters installed. Maybe tomorrow

 

Well, little update. I repaired the loom and checked for continuity in several locations, all appears to be okay. So far I got a used ABS module and plugged it in. It is recognized in GDS2 with a vxdiag nano, I am still waiting on the steering rack. However I am still unable to communicate with the ECM. I have the fenders pulled and there is no damage what so ever that got even close to the ECM. I know some have said that the rack can be removed and the ECM will still work, but I am hoping that it is actually not the case and once I get the steering module plugged in the ECM will wake up. If not I am leaning towards a completely new wiring harness which doesn't look like much fun to swap out, and if that doesn't work the possibility of a fried ECM.

 

Measure the resistance between pin 6 and pin 14 on the DLC. 60 ohms means the GMLAN is intact and you should be able to communicate with the ECM.

 

okay thanks I’ll give that a shot tomorrow and report back.

 

Resistance between 6 & 14 comes back at .1


Which if I understand correctly means my high and low can are shorted together somewhere. I’ll start by unplugging modules until the short goes away, if that doesn’t work time to reinspect that harness again.

 

Well I wasn’t thinking when I did that measurement. Had multimeter set wrong.

comes back at 120 ohms meaning on of the terminators is not showing up. Guessing the ecm and still have the distinct possibility that it’s the steering module preventing the final leg of the CAN being completed.

Volts on canH and canL are appropriate and add up to 5v. Not shorts to ground or + on either.

im just going to wait until steering rack shows up and see unless I can figure out how to bypass it. Thanks again. I’ll report back with more info.