Fletcher opened his eyes. " Pull up the ECU firmware version." He said. Chad tapped the diagnostic screen. A string of numbers appeared.
HY-BC.4.2.7-MOD. Fletcher shook his head. " That's your problem." " Right there." " What do you mean?"
Chad leaned in. " The Huayra BC shipped with firmware version 4.1.3. Pagani released an update 4.2.7 in late 2019. But 4.2.7 was designed for the Huayra Roadster BC, not the coupe. The coupe uses a different e-motor relay mapping, different voltage thresholds, different timing protocols."
Chad stared at the screen. His face went pale. " Someone installed the Roadster firmware on a coupe." Fletcher continued. " Probably during a routine service update.
The ECU thinks it's talking to a Roadster relay. The relay thinks it's listening to a coupe controller. They're speaking two different languages, and the system keeps throwing fault codes because neither side can agree on what normal looks like." Chad pulled up the service history on his tablet. His fingers were shaking.
He scrolled through months of entries, oil changes, brake inspections, tire rotations, until he found it. March 14th. Routine firmware update performed by Whitmore Motors service department. Firmware version HY-BC.4.2.7-MOD. " Oh my god."
Chad whispered. Todd looked over his shoulder. " We did this?" " We did this." Chad's voice was hollow. "
Eight months ago we installed the wrong firmware and nobody caught it." Through the glass, Victoria's expression hadn't changed, but her knuckles were white around her crossed arms. Fletcher was already moving to the second problem. He pulled a penlight from his jacket pocket, a small LED flashlight scratched and dented, the same one his grandfather used to carry. He leaned deep into the engine bay tracing the wiring harness from the hybrid relay to the temperature sensor cluster. "
Somebody hand me a mirror." Todd found a small inspection mirror in the tool drawer and passed it over. Fletcher angled it under the sensor housing. There it was. A single two-pin connector no bigger than a thumbnail.
The temperature sensor feed for the hybrid battery thermal management system. It was seated firmly. It looked correct. Every diagnostic scan in the world would say it was fine. But it was backwards. "
The polarity is reversed." Fletcher said. He held the mirror so Chad could see. " Positive and negative are swapped. See the color coding?
Red wire is on the black terminal. Black wire is on the red terminal." Chad crouched down and looked. His mouth opened. No words came out. "