P1621 - FAULT CODE - OBD2

P1621 Code failures by brands

P1621 BUICK, CADILLAC, CHEVROLET, GMC, PONTIAC, SATURN: CONTROL MODULE LONG TERM MEMORY PERFORMANCE CONDITION

Description of DTC code P1621

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.

Symptoms of fault code P1621

Check Engine light ON.

Causes of OBD2 P1621

Reasons for setting the P1621 OBD2 diagnostic code

The battery charge level may not be enough.
The PCM may be in poor condition.

Possible solutions of the DTC code P1621

To troubleshoot the P1621 OBDII DTC, try this:

Consult Technical Service Bulletins.
Check with a scanner if there are other DTCs set, especially those that refer to PCM problems. If this is the case, diagnose those codes first.
Check to see if the battery has the required charge level. Generally, this voltage should be between 12.5 and 12.9V. If this reading is not within the required levels, check that it is not due to damage to the battery wiring. Fix if necessary.
In many cases, the repair of the P1621 code involves the replacement of the Powertrain Control Module. We highly recommend repairing other DTCs before proceeding with this step.