P0606 — ECM/PCM Processor Fault

P0606 means the engine control module's internal self-test failed. Check power, grounds and for water intrusion before assuming the module itself is dead.

Cost range: $100–$2,000. Severity: high. Safe to drive? No. The module controlling the engine has reported itself unreliable.

Most common causes of P0606

1. Poor ground or corroded power connection — The cheapest and most overlooked cause — clean the engine ground straps. ($50–$200)
2. Water intrusion into the ECM — Common where the module sits low in the cowl or footwell. ($500–$1,800)
3. Low battery voltage or failing alternator — Brownouts trigger internal faults. ($150–$700)
4. Failed ECM/PCM — Requires replacement and programming to the vehicle. ($800–$2,000)

Symptoms drivers report with P0606

• No start
• Multiple unrelated codes
• Stalling
• Warning lights across the dash