DTC P1621: Shut Off Error (Reference Circuit Low, stabiliser limit exceeded)
- Check the ''On Board Diagnostic (OBD) System Check''.
Was the ''OBD System Check'' performed?
YES – Go to step 2.
NO – Go to OBD System Check. 
- Check the ECM ground circuit.
Was a problem found?
YES – Repair the ECM ground circuit.
NO – Substitute a known-good ECM and recheck. If symptom/indication goes away, replace the original ECM.
| NOTICE |
The battery power supply short circuit to 5 V power supply damages the ECM.