P0603

Showing the 60 model years where P0603 appears most; it is on file for 133 in total.

A model year appears here because the code is named in its record, not because every one of these vehicles sets it. Counts are mentions in the federal files, not failure rates — nobody publishes the denominator.

Owners’ own words, one per nameplate, scrubbed of anything identifying. These are unverified reports filed with NHTSA — they are what was said, not a finding that it was true.

Service bulletins and campaigns whose filed summary names P0603. Quoting the document number at a service desk is often the fastest route to a diagnosis someone has already written down.

• NTB21-027
  2021-04-01 · Engine And Engine Cooling
• MIL ON WITH DTC P062F AND/OR P0603 STORED IF YOU CONFIRM The MIL is ON and DTC P062F (EEPROM) and/or P0603 (ECM BACK UP/CIRCUIT) is stored, And The customer stated the vehicle was recently started after sitting for an extended period of time (i.e., the battery voltage was low while attempting to start the engine). ACTION 1. Test the vehicle’s 12 volt battery using the Midtronics DSS-50
• NTB16-018D
  2021-04-01 · Engine And Engine Cooling
• MIL ON WITH P0603 STORED FOR ECM BACK UP CIRCUIT This bulletin has been amended. See AMENDMENT HISTORY on page 3. Please discard previous versions of this bulletin.
• ITB21-007
  2021-04-01 · Engine And Engine Cooling
• MIL ON WITH DTC P062F AND/OR P0603 STORED IF YOU CONFIRM The MIL is ON and DTC P062F (EEPROM) and/or P0603 (ECM BACK UP/CIRCUIT) is stored, And The customer stated the vehicle was recently started after sitting for an extended period of time (i.e., the battery voltage was low while attempting to start the engine). ACTION 1. Test the vehicle’s 12 volt battery using the Midtronics DSS-500
• ITB16-008C
  2021-04-01 · Engine And Engine Cooling
• MIL ON WITH P0603 STORED FOR ECM BACK UP CIRCUIT This bulletin has been amended. See AMENDMENT HISTORY on page 3. Please discard previous versions of this bulletin.
• 18089
  2018-05-03 · Power Train
• 18089 - Service Update. On certain vehicles equipped with CVT Transmission (RPO MR8), the transmission control module (TCM) does not illuminate the MIL, and does not set the code P0603 (control module long term memory fault), when a memory checksum error identifies there is a malfunction of the Battery Independent Non-Volatile Dynamic Memory (BINVDM). This memory is used to store permanent DTC?s
• 18089
  2018-05-03 · Power Train
• 18089 - Service Update. On certain vehicles equipped with CVT Transmission (RPO MR8), the transmission control module (TCM) does not illuminate the MIL, and does not set the code P0603 (control module long term memory fault), when a memory checksum error identifies there is a malfunction of the Battery Independent Non-Volatile Dynamic Memory (BINVDM). This memory is used to store permanent DTC?s

A stored code names the test that failed, never the part that caused it. It is the starting point of a diagnosis, not its conclusion — the same code has several possible causes and the cheap one is not always right.