For 1990-2009 cars

### Circuit Description

The transaxle 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 Parameters

DTC P1621 will set if the TCM cannot communicate internally for a proper shut down when:

• | The ignition is in the RUN position.

• | The ignition voltage is 8-18 volts.

DTC P1621 is a type A DTC.

### Diagnostic Aids

• | The only possible repair is TCM replacement.

• | Program the replacement TCM with the correct software and calibrations.