What are the common causes of P065D?

A failed reductant warning lamp. An open or short in the lamp control circuit. Corrosion in the lamp wiring or connector. A failed reductant control module. A faulty ECM output.

Check the reductant warning lamp and its fuse. Inspect the lamp circuit wiring and connector. Command the lamp on with a scan tool. Scan the reductant control module for codes. Repair the control circuit if the lamp does not light. Clear the code and retest.

P065D

Reductant System Malfunction Lamp Control Circuit

System: Computer output circuits (P code)
Lamp: Check Engine Light
Category: Powertrain - Computer and Auxiliary Controls

What it means

P065D means Reductant System Malfunction Lamp Control Circuit.

Check these first

A failed reductant warning lamp
An open or short in the lamp control circuit
Corrosion in the lamp wiring or connector
A failed reductant control module
A faulty ECM output

What to do next

Check the reductant warning lamp and its fuse
Inspect the lamp circuit wiring and connector
Command the lamp on with a scan tool
Scan the reductant control module for codes
Repair the control circuit if the lamp does not light
Clear the code and retest

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Updated

Generic SAE J2012 definition. Last updated 2026-10-10.