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Home/DTC Codes/Chevrolet/Impala/2010-2010 3.5L V6/P1621
P1621

PCM Memory Performance (Long Term Memory Error)

2010-2010 Chevrolet Impala 3.5L V6

High SeverityPowertrain

The 2010 Chevrolet Impala is equipped with a 3.5L V6 engine. Below you'll find detailed p1621 diagnostic code information including labor time estimates, cost ranges, and technician notes specific to this engine configuration.

Description

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

  1. Check battery voltage and charging system
  2. Attempt PCM reflash/reprogram
  3. Check for aftermarket tuning devices
  4. Test PCM with factory scan tool
  5. 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.

Related Codes

P1600PCM Battery Direct Power CircuitP1600PCM Battery Direct Power CircuitP1600PCM Battery Direct Power CircuitP1600ECM Battery Backup CircuitP1600PCM Battery Direct Power CircuitP1600Loss of KAM Power — Open CircuitP1600PCM Battery Direct Power CircuitP1600Loss of KAM Power — Open CircuitP1600PCM Battery Direct Power CircuitP1600Loss of KAM Power — Open CircuitP1600Loss of KAM Power Circuit OpenP1600PCM Battery Direct Power CircuitP1600ECM Battery Backup CircuitP1600PCM Battery Direct Power CircuitP1600ECM Battery Backup CircuitP1625PCM System ResetP1625PCM System ResetP1625PCM System ResetP1625PCM System ResetP1625PCM System ResetP1625PCM System ResetP1625PCM System ResetP1625PCM System Reset

Other Powertrain Codes

P1621 on Other Vehicles

Chevrolet Astro

1996-1996 4.3L V6 Vortec

Chevrolet Astro

1997-1997 4.3L V6 Vortec

Chevrolet Astro

1998-1998 4.3L V6 Vortec

Chevrolet Astro

1999-1999 4.3L V6 Vortec

Chevrolet Astro

2000-2000 4.3L V6 Vortec

Chevrolet Astro

2001-2001 4.3L V6 Vortec

Chevrolet Astro

2002-2002 4.3L V6 Vortec

Chevrolet Astro

2003-2003 4.3L V6 Vortec

Common Questions

What does code P1621 mean on a 2010-2010 Chevrolet Impala?

P1621 stands for "PCM Memory Performance (Long Term Memory Error)". 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.

What are the symptoms of P1621 on a Chevrolet Impala?

Common symptoms of P1621 include: Check Engine Light, Various drivability issues, Possible stalling, Possible no-start condition, Loss of learned values, Erratic behavior.

What causes P1621 on a 2010-2010 Chevrolet Impala?

Common causes of P1621 include: Internal PCM/ECM failure, Low battery voltage during operation, Battery disconnection during critical write operation, Corrupted PCM software/calibration, Aftermarket tuning device issue.

Last updated: March 2026

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