P1621high severityPowertrain
PCM Memory Performance (Long Term Memory Error)
on 2016 Chevrolet Spark EV Electric Motor · FWD
What this code means
The PCM detected an internal memory fault in its EEPROM (Electronically Erasable Programmable Read Only Memory). The PCM stores critical adaptive and calibration data in this memory.
Symptoms
- Check Engine Light
- Various drivability issues
- Possible stalling
- Possible no-start condition
- Loss of learned values
- Erratic behavior
Common causes
- Internal PCM/ECM failure
- Low battery voltage during operation
- Battery disconnection during critical write operation
- Corrupted PCM software/calibration
- Aftermarket tuning device issue
Diagnostic steps
- Check battery voltage and charging system
- Attempt PCM reflash/reprogram
- Check for aftermarket tuning devices
- Test PCM with factory scan tool
- Verify PCM software version
Repair notes
Try PCM reprogramming first. If memory error persists, replace PCM. Ensure battery is fully charged before any PCM service.
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