P065D: Reductant System Malfunction Lamp Control Circuit

What Does The P065D Code Mean?

A stored code P065D means that the powertrain control module (PCM), or one of the other related controllers, has detected a discrepancy in the reductant system malfunction lamp control circuit.

The reductant system malfunction lamp is an integral part of the instrument panel. It is designed to warn the driver of a fault in the reductant system. Typically, the PCM receives a signal from one of the reductant system sensors. Reductant system sensors allow the PCM to monitor the reductant system for malfunctions.

When reductant system data is calculated by the PCM, and a problem is detected, the PCM emits a voltage signal to the reductant system malfunction warning lamp via the lamp control circuit. When the reductant system malfunction control lamp circuit is activated, the reductant system malfunction lamp should be illuminated.

When the key is placed in the on position (with the engine off) a self test is initiated for all instrument panel warning lamps. If a problem is detected in monitoring the reductant system malfunction lamp control circuit, a code P065D will be stored and a malfunction indicator lamp (MIL) may be illuminated.

What Are The Symptoms Of The P065D Code?

Symptoms of a P065D trouble code may include:

• Inoperative reductant system
• Reductant system malfunction lamp is inoperative
• Reductant system malfunction lamp remains illuminated
• Engine drivability issues
• Catalytic converter codes

What Are The Potential Causes Of The P065D Code?

Causes for this code may include:

• Defective reductant system malfunction lamp bulb
• Open or shorted circuit between the PCM and the instrument panel or other controllers
• PCM programming error
• Faulty controller or PCM

How Serious Is This P065D Code?

A P065D should be categorized as severe because it could result in an inoperative reductant system, catalytic converter damage, and/or drivability issues.

How Can You Fix The P065D Code?

If other reductant system codes are stored, these should be diagnosed and repaired before attempting to diagnose a P065D.

Consult your vehicle information source for technical service bulletins (TSB) that replicate the code stored, vehicle (year, make, model, and engine), and symptoms exhibited. If you find the appropriate TSB, it may yield helpful diagnostic information.

A diagnostic scanner and a digital volt/ohmmeter will be necessary to accurately diagnose a code P065D. A reliable source of vehicle information will also be required.

Retrieve All Stored Codes

Begin by connecting the scanner to the vehicle diagnostic port and retrieving all stored codes and freeze frame data. You will want to write this information down, just in case the code proves to be an intermittent one.

Clear The Codes And Test Drive

After recording all pertinent information, clear the codes and test drive the vehicle (if possible) until the code is reset or the PCM enters readiness mode.

If the PCM enters readiness mode, the code is intermittent and will be even more difficult to diagnose. The condition, which caused the P065D to be stored, may need to worsen before an accurate diagnosis can be reached. On the other hand, if the code fails to reset and there are no drivability symptoms exhibited, the vehicle can be operated normally.

Visually Inspect The Related Wiring And Harnesses

If the P065D is immediately reset, proceed with a visual inspection of system related wiring and connectors. Harnesses that have been broken of unplugged should be repaired or replaced as required.

If wiring and connectors appear functional, use your source of vehicle information to obtain the appropriate wiring diagrams, connector face views, connector pin-out charts, and diagnostic flow charts.

Se Your DVOM To Test The Reductant System Malfunction Lamp Control Circuit

Once you have the correct information, use your DVOM to test the reductant system malfunction lamp control circuit at the appropriate pin of the PCM connector. If no reductant system malfunction lamp control output signal is discovered, suspect that the PCM is defective or there is a PCM programming error.

If a reductant system malfunction lamp control output signal is discovered at the PCM connector, test the corresponding circuit (as it is presented) at the reductant system malfunction lamp control circuit pin of the instrument panel connector.

If the reductant system malfunction lamp control output signal is not discovered, you have an open circuit between the PCM and the reductant system malfunction lamp in the instrument panel. Repair or replace the circuit and retest.

• If the reductant system malfunction lamp fails to illuminate with the key and engine off, suspect reductant system malfunction lamp bulb failure
• If a code P065D is stored and the reductant system malfunction lamp is operational, suspect a defective PCM or a PCM programming error

Recommended Parts

Below are some recommended auto parts to help you address the trouble code affecting your vehicle and get it running smoothly again:

>>> WORKPRO 582-piece Crimp Terminals, Wire Connectors, Heat Shrink Tube, Electrical Repair Kit
>>> ECU
>>> INNOVA 5210
>>> KAIWEETS Digital Multimeter

Note: During the purchasing process, please check carefully whether the part you want to buy fits your car!

Reference Sources

P065D Reductant System Malfunction Lamp Control Circuit, OBD-Codes.