A10A

What the Code Means

A10A belongs to the Car Access System 3 (CAS) module and stands for “EWS4 timing challenge/response error” — a timing challenge/response mismatch between CAS and EWS4. The freeze-frame data lists “Signal or value below threshold.”

The fault is not currently present at the time of reading, and the check conditions are met. No warning lamp comes on for this code. According to the E90Post discussion, the code returns after clearing even on a stock car; one member had it block the time and temperature display on the instrument cluster.

Symptoms

• A10A stores and returns after clearing, including on a stock car.
• No warning lamp comes on for this code.
• Diagnostics show the fault is not currently present, and the check conditions are met.
• The time and temperature display on the instrument cluster may be overridden.

Diagnosis and Repair

1. Clear the code and rerun diagnostics with a more advanced scanner; the discussion mentions ISTA+.
2. Check the connections, grounds, and crankshaft sensor after the work performed.
3. To fix the no-start, the discussion required correct installation/replacement of the HPFP and priming of the fuel rail.

Secondary Damage

• HPFP damage from reinstalling it without manually turning the engine to bottom dead center; a new OEM Bosch HPFP was installed in the end (the budget replacement option).