Just had 12 v battery replaced at 5 years in my 2021. Apparently after a battery replacement, the VCIM can be stuck in partial boot mode. It needs to have a "VCIM firmware reflash using GDS2" says AI. The failure is noticed in the app where fuel and/or oil life may not show correctly.

 

Id try pulling the negative battery cable off for 15 min then reconnecting before anything else.

 

Per Copilot:

On the C8, the telematics module (VCIM) has its own internal power reserve and non-volatile memory. When you disconnect the 12V battery:

o The VCIM does not fully power down
o It does not clear its boot state
o It does not re-register on the CAN bus
o It does not reload firmware

So even if you leave the battery disconnected for 15 minutes...
or 30 minutes...
or overnight...

...the VCIM will come back in the exact same corrupted state it was in before.

 

Battery concerns can be frustrating to deal with and we want the chance to look into this matter with you further, Dave. Please send us an email at socialmedia@gm.com with “davelv Corvette Forum” the subject line, then provide additional details about your experience in the body of the email. We will wait for your contact.

 

I'd trust Copilot/AI about as far as I can throw that battery.

First time I've heard of such an issue on a C8 battery change.

 

The TCICM has a back up battery, but it will not provide power to the TCICM if the 12V starting battery is disconnected properly. I have no comment about the "boot state', or registering on the bus, etc....many many have changed out a battery without issue.


The telematics communication interface control module, or TCICM, as it is described in the Service Manual, does have a backup battery and there is even a replacement procedure for it. But.....it does not kick in unless the battery is disconnected while the car is still on or retained power accessory is active, and even then if it does not detect collision or near-collision event, backup battery power circuits are disconnected, preventing dis-charge of the battery. Procedures in manual that involve disconnecting the 12v starting battery even include a caution:

"Do not disconnect the main vehicle battery or remove the OnStar® fuse with the ignition key in any position other than OFF. Retained accessory power should be allowed to time out or be disabled (simply opening the driver door should disable retained accessory power) before disconnecting power. Disconnecting power to the OnStar® module in any way while the ignition is On or with retained accessory power activated may cause activation of the OnStar® Back-Up Battery system...."



I have no comment about the "boot state', or registering on the bus, etc....many many have changed out a battery without issue.


The details of the backup battery design and function vary with configuration - the description below is from the section in the manual describing the OnStar system for vehicles with UE1 (OnStar) and either IOS (RADIO-INFOTAINMENT SYSTEM - 3.X MID/HIGH HMI, ENHANCED CONNECTIVITY, VOICE RECOGNITION, MID SD NAV CAPABLE) or IOT (RADIO-INFOTAINMENT SYSTEM - 3.X MID/HIGH HMI, ENHANCED CONNECTIVITY, VOICE RECOGNITION, PREMIUM SD NAV) and is applicable to our US vehicles. Other descriptions vary with respect to what happens if.when the TCICM backup battery is activated, but all of them say that the back up battery only kicks in if the main power is cut while the car is on. Here is the description for UE1 with IOS/IOT:

"In some vehicles, the Telematics system is equipped with a Back-Up Battery (BUB) installed inside the TCICM. This battery is a two-cell lithium ion rechargeable battery assembly, connected with a short electrical harness, to the circuit board in the module. Contained within this two-cell battery package are a temperature-sensing thermistor, automatic-resetting circuit-overload protection, and a low-pressure vent valve. Nominal voltage of the battery pack is 7.3 Volts. The BUB is only switched into service when the Telematics system is in normal On condition, vehicle power mode of either Run or On, and main vehicle battery power (B+) at the TCICM suddenly becomes near-zero. At this time BUB power is connected to the main circuit board power using solid-state power switching circuits. After initiating BUB for module power, the GMLAN bus is monitored for a message confirming a collision-event, or near-collision event, has occurred. If a confirmation message is received, the TCICM continues to use BUB as the power supply until it is depleted. If a confirmation message is not received within 10 seconds, the BUB power circuits are internally disconnected, preventing inadvertent dis-charge of the battery. Charging circuitry within the TCICM maintains the state of charge of the BUB. BUB charging occurs as determined by the module software, primarily based on temperature and state of charge. Battery state of charge is measured by the telematics module circuitry, and remaining energy capacity calculated by the module software. On board diagnostic tests check for circuit faults, over-temperature conditions, and low-energycapacity. Current DTCs will set for each of these conditions. No component checks are required, and are not recommended, for BUB diagnosis."

Here is an illustration from the replacement procedure - showing where it goes:

 

Thanks for the info.

I'll let dealership fix it since they replaced the battery.