Temperature problem?

[Infinion]

It's a pity error PС078 covers many other faults that cannot be detected by the scanner, I found the cause of the faulty module that was blocking everything, the repair took a long time

Hey glad you resolved your issue! Could you give some more info on the solution?

Which module was it? Was it sucking power and causing precharge to fail then? What did you do to repair it? Did you replace the module?

It's a pity error PС078 covers many other faults that cannot be detected by the scanner

What scanner were you using? If it was a generic OBDII scanner and a limited app, you might only see generic codes. I imagine an OBDLink LX with the enhanced OEM trouble code add-on for ~$15 or a VCX Nano to read and clear permanent or hidden DTCs using GDS2 protocol would probably find more detailed and specific codes for you to work with.

If all it told you was precharge fail, then any of the high voltage modules could have been a culprit, the 400V DC- 12V DC APU , the high voltage coolant heaters, the compressor, or the on-board charger.

I'm going to play catch up with your previous post, it might be useful in some way.

I completed the entire process of resetting errors. I checked the battery charge at 12.5 volts. After resetting the errors, I disconnected the battery. I turn on the ignition, errors P0C78 --failed precharge, P0ABC --low voltage on battery engine control module sensing circuits. P0A0C -- interlock loop is disconnected somewhere. U1861 --communication lost between modules. P1E00 -- malfunction indicator light requested by the HPCM2 which could indicate other hidden codes exist .

Considering you got P0A0C -- the interlock loop DTC -- right after you were working on the 12V battery, you might have left the engine shroud off. It has a bolt on the right-hand side that has to be screwed in place to complete the interlock loop. Or if you disconnected the high voltage service disconnect but didn't reconnect or seat it properly, that code would come on too.

The other codes you got in this post point to a variety of areas and parts related to the hybrid powertrain control module 2 in one way or another. Mostly sounds like a communication hiccup from an anomalous state after the hard reset of the 12V computers from the battery pull or the precharge issue, or both. And U1861 says as much, that communication was lost between modules. Could that indicate damage in a braided pair of communication cables, maybe. Otherwise its probably fine to ignore and clear.

I have a question for you: perhaps the absence of motor 94558478 and error U0284 affect other errors. After all, I drove exactly 10,000 km without this part?

The Grill shroud motor? The 10k km is probably a coincidence. It's an American car that is converting miles to km, so that nice round 10k is actually 6213.7 miles, hardly a significant number. And if you drove 10k km without it, it means you passed the precharge phase a bunch of times without being denied the EV Ready status that lets you drive at all.

I think the absence of the grill shroud motor or the shroud itself would cause cause poor aerodynamic efficiency and too much (or too little) passive cooling while driving, but I don't think it's a critical component for drivetrain function that would ever lock you out of driving...

 

[gazik75]

Errors read DGS2 gm mdi and scanner (launch) wrote everything in the same way, solved the problem by disconnecting the high-voltage connectors from the fuse block, the car started after turning off the pre-heater

 

[Infinion]

Errors read DGS2 gm mdi and scanner (launch) wrote everything in the same way, solved the problem by disconnecting the high-voltage connectors from the fuse block, the car started after turning off the pre-heater

Thanks for sharing that. If the coolant heater is causing problems, you might want to check to see if the communication cable is damaged

The fuse block should not have any high-voltage connectors, the voltages are automotive '12V' only. You must be referring to the Power Control Module (also known as the High Power Distribution Module) directly under the plastic engine cover shroud. That distribution module houses the high voltage bus bars where all the HV module cabling meets, 3 cartridge fuses for the CHCM to denote Coolant Heater Control Module (30A) , ACCM to denote A/C compressor (30A), and APM to denote the Accessory Power Module (12A, HVDC - 12VDC converter), and the optional high side and low side contactors for DC Fast Charging. The "pre-heater" would have a connector located on the side of the PCM labeled as "CHCM". There is another PTC coolant heater with its own dedicated coolant loop for the battery, but this is connected elsewhere.
Here are some images and schematics for reference. I included the interlock loop as well.

You could also inspect circuit 5060 leading to the heater module, as well as the F10UA fuse in the fuse block to check its condition

 

[gazik75]

turned off the high-voltage CHCM. I measured the resistance on it and it was 3 ohms On
the case I changed this block 22851153. Sorry I can't add a photo here