P1604 — Startability Malfunction
CAUTIONIs it safe to drive? Drive gently and get it looked at soon — it can worsen or fail inspection.
What P1604 means
This is a manufacturer-specific code — its meaning depends on the vehicle’s make (see below).
What P1604 means on specific makes
Toyota / Lexus / Scion CAUTION
The ECM detected the engine struggled to start or nearly stalled right after starting. It's a symptom code pointing to fuel, ignition, or air-metering problems rather than one specific part.
- Weak fuel delivery / dirty injectors
- Ignition weakness (coils/plugs)
- Vacuum/intake leak
- MAF or coolant temp sensor skew
Check first: Look for stored companion codes and watch fuel trims and ignition at cold start; diagnose the underlying hard-start cause.
Source: engine-codes.com/p1604_toyota.html