P0604high severityPowertrain
Internal Control Module Random Access Memory (RAM) Error
on 1998 Toyota Tacoma 2.7L I4 · RWD
What this code means
The PCM detected an internal RAM read/write fault during self-testing. This typically points to an internal processor or memory failure within the module.
Symptoms
- Check engine light on
- Poor engine performance
- Intermittent stalling or no-start
Common causes
- Faulty PCM internal RAM
- Internal module hardware failure
- Voltage supply instability
- Corrupt module software
Diagnostic steps
- Verify battery and charging system voltage
- Check PCM power and ground circuits
- Clear code and monitor for recurrence
- Reflash or replace PCM if fault remains
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