P1621 GMC Control Module Long Term Memory Performance Condition

Possible causes

– Faulty Powertrain Control Modules (PCM)
– Low car battery voltage

When is the obd code mean?

If the checksum of the Electronically Erasable Programmable Read Only Memory (EEPROM) does not match a predetermined value by the Powertrain Control Modules (PCM), DTC P1621 will set.

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)

P1621 GMC OBD Code Description