Reductant Control Module Supply Voltage Circuit

Where it lives

For P21CA, the module sits on the circuit this code reports. The description of P21CA reports a fault at the module.

Check these first

• A short or open in the reductant control module supply voltage feed
• Corrosion or backed out pins at the reductant control module connector
• Low battery voltage or a weak charging system dropping module supply
• A failed reductant control module pulling its own supply down

What to do next

1. Read reductant control module supply voltage on a scan tool
2. Test the supply feed to the reductant control module under load
3. Check the module ground and connector pins for corrosion
4. Load test the battery and charging system
5. Replace the reductant control module if the supply and ground test good
6. Clear the code and retest

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