Here's why you're seeing this and what's likely damaged:
* Controller Area Network (CAN) Bus Failure: The "NO Bus" message indicates a problem with the CAN bus, the communication network connecting various electronic control units (ECUs) in your vehicle. The reverse polarity likely damaged components within these ECUs or the wiring harnesses connecting them, disrupting communication.
* BCM Damage: The Body Control Module (BCM) is a central hub managing many electrical functions. It's extremely vulnerable to reverse polarity, and its failure would explain the lack of gauge function and other electrical anomalies.
* ECU Damage: Various Engine Control Modules (ECMs) and other ECUs are likely also damaged. This would prevent the engine from starting and explain the various symptoms.
* Wiring Harness Damage: The reverse polarity could have damaged the wiring harness itself, creating open circuits or shorts that prevent communication and power flow. This is less likely to be the *sole* cause but could contribute significantly.
* Fuses: While you checked fuses, some may be slow-blow types that didn't immediately fail but are internally damaged. Also, the damage may be *after* the fuses, within the circuits themselves. Replacing fuses won't necessarily fix the problem if the problem is in the circuitry *after* the fuses.
Why no blown fuses immediately apparent? Reverse polarity damage isn't always immediately obvious with blown fuses. The surge can damage components gradually, leading to failures later, or cause internal shorts that draw excessive current without blowing fuses outright. The damage is often insidious and reveals itself over time.
What to do:
1. Professional Diagnosis: This is absolutely critical. You need a mechanic with experience in automotive electronics and diagnostics to thoroughly assess the damage. A simple multimeter check won't suffice; specialized diagnostic tools are needed to test the CAN bus and the various ECUs.
2. Don't attempt further repairs yourself: Continuing to troubleshoot without the proper knowledge could cause further damage. The reverse polarity jump has potentially caused extensive damage.
3. Prepare for significant repair costs: Repairing the damage from a reverse polarity jump can be expensive, involving replacement of ECUs, wiring harnesses, or even the BCM. The cost could exceed the value of the vehicle, depending on the extent of the damage and the vehicle's condition.
In short, the "NO Bus" message is a serious warning sign, and you should not attempt to start the vehicle or perform any further electrical work until a qualified mechanic has assessed the damage.
