Reductant Quality Module Supply Voltage Low

Where it lives

For P21CD, the circuit described runs through the module. The description of P21CD reports low voltage at the module.

Check these first

• A low supply feed to the reductant quality module
• High resistance in the reductant quality module ground circuit
• A discharged battery or failing alternator starving the module
• A failed reductant quality module drawing excess current

What to do next

1. Read reductant quality module supply voltage on a scan tool
2. Measure the module supply feed for voltage drop
3. Check the module ground strap and connector pins
4. Test the battery and charging system output
5. Replace the reductant quality module if the feed and ground are good
6. Clear the code and retest

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