Have trouble code P1621 - 1998 Pontiac Sunfire

When you disconnect the battery, you need to reset the security and immobilizer.

https://www.google.com/search?q=2003+Peugeot+307+cc+2.0+reset+security

Peugeot 307 P1621 Engine Trouble Code

http://p1621.enginetroublecode.com > peugeot-307
P1621 engine trouble code is about Crankshaft Position Sensor A Circuit Low Input. Reason For P1621 Code. The reason of P1621 OBD-II Engine Trouble Code is Fuel ...

P1621 and clogged DPF - Peugeot Forums

https://www.peugeotforums.com > threads > p1621-and...
Mar 26, 2021 - Hi there. I've been having some issues with my otherwise lovely 2012 Peugeot 5008 (1.6) lately. The engine-light comes on aswell as the esp ...

Peugeot 3008 Sid807 dtc p1621 after mod - MHH AUTO

https://mhhauto.com > Thread-Peugeot-3008-Sid807-dt...
Jan 24, 2019 - Today I've took the car to dealer and he says after update car still the same. Anyone know what I can try to do now? Dtc p1621 is Inchoerence ...
4 posts · Hello.maybe someone can help me. I've sid807 for fap remove. Opened ecu, read backup by pcmflash ...
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More results from mhhauto.com

https://www.engine-codes.com/p1621.html

This site has several possibilities including low voltage to the electrical system causing various drivability problems.

P1621 Chevrolet Control Module Long Term Memory Performance Condition

C?digo P1621 Problema significa : control del motor de inmovilizaci?n del motor m?dulo de mal funcionamiento del circuito de entrada.

TYPE: OBD P1621

Is your battery no good?

I would disconnect the battery for a few min then hook it back up to see if it resets itself. if not you have bad cell in the battery and needs to be replaced. good luck

Trouble code P1621 means: Engine control module engine immobilization input circuit malfunction The Transmission Control Module (TCM) contains various types of memory to gather and share information internally. At shut down, the TCM stores information in memory to prepare for the next ignition cycle. When the TCM cannot communicate internally, DTC P1621 sets. DTC P1621 is a type A DTC.

DTC PARAMETERS
DTC P1621 will set if the TCM cannot communicate internally for a proper shut down.

DIAGNOSTIC AIDS
The suggested repair is TCM replacement. Remember to program the replacement TCM with the correct software and calibration. however Ive know loose positive battery cable to toss out that code, so check your connections

A vehicle control module (VCM) or powertrain control modules' (PCM) electronically erasable programmable read only memory (EEPROM) contains data essential to running the engine and transmission. The VCM/PCM stores critical preprogrammed data within the EEPROM, this data remains even if the vehicles' battery is disconnected. At power up the VCM/PCM checks the integrity of this data. If the checksum of the EEPROM does not match a predetermined value, DTC P1621 will set. The DTC will also set if the VCM/PCM is unable to correctly read or finds corrupt data from the EEPROM. GM recommends testing/replacement of the VCM/PCM using required equipment by a qualified technician for this type of VCM/PCM memory performance fault condition.

That code is for Engine control module engine immobilization input circuit malfunction. Ignition coil is ok.

The code means the engine control module imobilisation function is active.
can you describe what the car is doing and after you scanned the code did you try to reset it?
If so and there is no difference it may be a dealer reset only and you may have a bad ecu (water ingress?)
JPTCAT