Technical Description of OBD-II Trouble Code
Control Circuit for Malfunction Lamp in the Reductant System
What does that signify?
This is a generic diagnostic trouble code (DTC) that is applicable to many OBD-II vehicles (1996-newer). This includes vehicles from VW, Audi, Chevrolet, Chrysler, Ford, Dodge, GMC, Ram, Volkswagen, etc. Although it is a generic code, the specific repair steps may vary depending on the year, make, model, and powertrain configuration.
A stored code P065D indicates that the powertrain control module (PCM) or one of the related controllers has detected an inconsistency in the control circuit for the malfunction lamp in the reductant system.
The reductant system malfunction lamp is an essential component of the instrument panel. Its purpose is to alert the driver of a fault in the reductant system. Typically, the PCM receives a signal from one of the reductant system sensors. These sensors enable the PCM to monitor the reductant system for malfunctions. When the PCM calculates reductant system data and detects a problem, it sends a voltage signal to the reductant system malfunction warning lamp through the lamp control circuit. When the reductant system malfunction control lamp circuit is activated, the reductant system malfunction lamp should illuminate.
When the key is turned to the on position (with the engine off), a self-test is initiated for all instrument panel warning lamps. If there is an issue in monitoring the reductant system malfunction lamp control circuit, a code P065D will be stored and a malfunction indicator lamp (MIL) may illuminate.
A reductant DEF tank:
What is the severity of this DTC?
A P065D should be considered severe because it could lead to an inoperative reductant system, damage to the catalytic converter, and/or drivability problems.
What are some of the symptoms of the code?
Symptoms of a P065D trouble code may include:
What are some of the common causes of the code?
Possible causes for this code may include:
What are some P065D troubleshooting steps?
If there are other stored reductant system codes, it is recommended to diagnose and repair those before attempting to diagnose a P065D.
Refer to your vehicle information source for technical service bulletins (TSB) that match the stored code, vehicle details (year, make, model, and engine), and exhibited symptoms. If you find the relevant TSB, it may provide helpful diagnostic information.
To accurately diagnose a code P065D, you will need a diagnostic scanner and a digital volt/ohmmeter. You will also require a reliable source of vehicle information.
Start by connecting the scanner to the vehicle’s diagnostic port and retrieving all stored codes and freeze frame data. It is advisable to write down this information in case the code proves to be intermittent.
After recording all relevant information, clear the codes and, if possible, test drive the vehicle 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 challenging to diagnose. The condition that caused the P065D to be stored may need to worsen before an accurate diagnosis can be made. On the other hand, if the code fails to reset and there are no drivability symptoms, the vehicle can be operated normally.
If the P065D is immediately reset, proceed with a visual inspection of the wiring and connectors related to the system. Repair or replace any broken or unplugged harnesses as necessary.
If the wiring and connectors appear to be functioning properly, use your vehicle information source to obtain the appropriate wiring diagrams, connector face views, connector pin-out charts, and diagnostic flow charts.
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 detected, suspect that the PCM is defective or there is a PCM programming error.
If a reductant system malfunction lamp control output signal is detected at the PCM connector, test the corresponding circuit (as 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 detected, there is an open circuit between the PCM and the reductant system malfunction lamp in the instrument panel. Repair or replace the circuit and retest.
