What does it mean?
This is a generic diagnostic trouble code (DTC) and applies to many OBD-II vehicles (1996-newer). This may include, but is not limited to, vehicles from VW, Audi, Chevrolet, Chrysler, Ford, Dodge, GMC, Ram, Volkswagen, etc. Although generic, the exact repair steps may vary depending on the year, make, model, and powertrain configuration.
A stored P065D code means that the Powertrain Control Module (PCM), or one of the other related controllers, has detected an anomaly in the reductant system malfunction indicator lamp control circuit.
The reductant system malfunction indicator lamp is an integral part of the instrument cluster. It is designed to warn the driver of a reductant system failure. Typically, the PCM receives a signal from one of the reductant system sensors. The reductant system sensors allow the PCM to monitor the reductant system for any malfunction. When reductant system data is calculated by the PCM and a problem is detected, the PCM sends a voltage signal to the reductant system malfunction warning lamp via the lamp control circuit. When the reductant system malfunction indicator lamp circuit is activated, the reductant system malfunction lamp should illuminate.
When the key is turned to the ON position (engine off), a self-test is initiated for all instrument cluster warning lamps. If a problem is detected in the monitoring of the reductant system malfunction indicator lamp control circuit, a P065D code will be stored and a Malfunction Indicator Lamp (MIL) may illuminate.
A reductant DEF tank:
P065D Reductant DEF Tank
How severe is this DTC?
A P065D should be classified as severe because it could lead to an inoperative reductant system, damage to the catalytic converter, and/or driving issues.
What are some of the symptoms of the code?
Symptoms of a P065D trouble code may include:
Inoperative reductant system
The reductant system malfunction lamp is inoperative
The reductant system malfunction indicator remains illuminated
Engine driving issues
Catalytic converter codes
What are some common causes of the code?
Causes
of this code may include:
Faulty reductant system malfunction lamp bulb
Open or shorted circuit between the PCM and the instrument cluster or other controllers
PCM programming error
Faulty controller or PCM
What are the troubleshooting steps for P065D?
If other reductant system codes are stored, these should be diagnosed and repaired before attempting to diagnose a P065D.
Consult your vehicle’s information source for Technical Service Bulletins (TSBs) that match the stored code, the vehicle (year, make, model, and engine), and the symptoms presented. If you find the appropriate TSB, it may provide helpful diagnostic information.
A diagnostic scanner and a digital volt/ohmmeter will be needed to accurately diagnose a P065D code. A reliable source of vehicle information will also be required.
Start by connecting the scanner to the vehicle’s diagnostic port and retrieve all stored codes and freeze frame data. You will want to note this information, just in case the code proves to be intermittent.
After recording all relevant information, clear the codes and test drive the vehicle (if possible) until the code resets 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 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 does not reset and no driving symptoms manifest, the vehicle may be operating normally.
If the P065D resets immediately, proceed with a visual inspection of the wiring and connectors related to the system. Harnesses that are broken or disconnected should be repaired or replaced as necessary.
If the wiring and connectors appear functional, use your vehicle information source to obtain the appropriate wiring diagrams, connector face views, connector pinout diagrams, and diagnostic flowcharts.
Once you have the correct information, use your DVOM to test the reductant system malfunction indicator lamp control circuit at the appropriate PCM connector pin. If no reductant system malfunction lamp control output signal is found, suspect a faulty PCM or a PCM programming error.
If a reductant system malfunction lamp control output signal is found at the PCM connector, test the corresponding circuit (as presented) at the instrument cluster connector’s reductant system malfunction indicator lamp control circuit pin. If the reductant system malfunction lamp control output signal is not found, you have an open circuit between the PCM and the reductant system malfunction lamp in the instrument cluster. Repair or replace the circuit and retest.
If the reductant system malfunction indicator does not illuminate with the key on and engine off, suspect a faulty reductant system malfunction indicator bulb
If the P065D code is stored and the reductant system malfunction lamp is operational, suspect a faulty PCM or a PCM programming error