P1621 BUICK, CADILLAC, CHEVROLET, GMC, PONTIAC, SATURN: CONTROL MODULE LONG TERM MEMORY PERFORMANCE CONDITION
POST UPDATED IN January, 2023
P1621 BUICK, CADILLAC, CHEVROLET, GMC, PONTIAC, SATURN: CONTROL MODULE LONG TERM MEMORY PERFORMANCE CONDITION
The Powertrain Control Module (PCM) checks the integrity of the EEPROM (Electrically Erasable Programmable Read-Only Memory) non-volatile memory area. To do this, the PCM uses the EEPROM to store information with the key Off.
Besides, there are several locations for data storage within the non-volatile area. In case the PCM finds a problem in the EEPROM location, this control module will try to store the data in another location. If the PCM detects a failure in non-volatile memory, it will set a fault code that warns of the situation. The P1621 OBDII code means that the memory has run out of valid locations for storing this data.
It is important to remark that the PCM stores a copy of the previously stored key ON values in non-volatile memory. When this code is set, the PCM will default to the information already stored, and the driver will not notice any difference in the vehicle operation.
Reasons for setting the P1621 OBD2 diagnostic code
To troubleshoot the P1621 OBDII DTC, try this: