P2258 Code on Cold Starts in 2014 Mercedes-AMG C63: Secondary Air Pump & Valve Diagnosis

I'm experiencing a consistent P2258 fault code only during cold starts on my 2014 Mercedes-AMG C63. The issue is intermittent but reliably reproducible under specific conditions. Here's what I've diagnosed so far: - The P2258 error occurs exclusively during cold starts, with one opportunity per day to trigger the code. - Error codes include: - P2258: AIR System Control A Circuit High - 1065: Secondary Air Valve 1 has a short circuit to positive I use iCarSoft V2 to monitor system parameters and valve states. The air injection system relay, fuse (40A), and pump function have all been verified — the pump operates correctly when tested directly. I replaced both the secondary air switching valve 1 and swapped valve 2 with the previously removed one. Despite these changes, P2258 persists specifically for valve 1. After removing both switching valves during a cold start, I observed that the ECU reports electrical faults on both secondary air valves (valve 1 and 2), suggesting no major wiring issues in the harnesses or connections. Additionally, airflow-related error codes appear for both engine banks — indicating normal secondary airflow behavior. System operation appears functional: after a cold start, I observe: - The P2258 code triggers immediately. - After ~2–3 minutes of idle, the air pump ramps to 50% speed and valve 1 opens (confirmed via iCarSoft). - A few seconds later, the air pump reaches 100%, and valve 2 opens. - This state lasts about 5 seconds before the system shuts down and fails to re-activate for the remainder of the day or until reset. I've tested the switching valves with a multimeter — consistently reading 8.4V when ignition is on, but no activation occurs after idle due to failure in valve detection by the ECU. Visual inspection confirms all wiring and connections are intact, with no visible damage in the engine bay. The car has only covered 19k miles and has a clean engine bay. I previously had secondary catalytic converters removed (a common modification on this model), which may have contributed — though I cannot confirm if this is directly linked to the issue. The P2258 code triggers 100% during cold starts, and EML (Engine Malfunction Light) activates after two or three occurrences without clearing. I haven't tested any vacuum metal valves yet, but based on my observations, the system appears to be operating correctly in terms of timing and activation. My next step is to monitor voltage levels at both air valve connectors during a cold start to verify consistency between valve 1 and valve 2 — as the code only manifests for valve 1. I'm currently stumped and open to any expert insights or diagnostic suggestions. I’m ready to proceed with further testing if needed.