P0648 Immobilizer Lamp Control Circuit
OBD-II Trouble Code Technical Description
Immobilizer Lamp Control Circuit
What does that mean?
This is a generic diagnostic trouble code (DTC) and applies to many OBD-II vehicles (1996-newer). That may include but is not limited to vehicles from Acura, Buick, Chevrolet, Chrysler, Dodge, Ford, GMC, Hyundai, Kia, Honda, etc. Although generic, the exact repair steps may vary depending on year, make, model and powertrain configuration.
A stored code P0648 means that the powertrain control module (PCM) has detected a malfunction in the immobilizer lamp control circuit.
The immobilizer lamp is contained in the instrument panel. Its primary function is to warn the driver that the immobilizer key has malfunctioned or is not recognized (when it is illuminated). This warning lamp is sometimes referred to as the security lamp.
The PCM typically monitors the continuity of the immobilizer lamp control circuit whenever the ignition is turned on. The immobilizer key is equipped with a transponder that is recognized by the PCM (and other controllers) when it is in close proximity to the vehicle. This allows various systems (such as push-to-start and keyless entry) to remain functional and practical.
Each time the ignition is turned on and the PCM is energized, multiple controller self-tests are performed. In addition to running internal controller self-tests, the controller area network (CAN) carries serial data from each individual module to ensure that on-board controllers are interfacing properly.
If a problem is detected in monitoring the immobilizer lamp control circuit, a code P0648 will be stored and a malfunction indicator lamp (MIL) may be illuminated.
A typical immobilizer lamp:
What is the severity of this DTC?
Internal control module codes should be taken seriously. A stored code P0648 (with immobilizer lamp illumination) will likely result in a no start condition.
What are some of the symptoms of the code?
Symptoms of a P0648 trouble code may include:
No start Immobilizer lamp inoperative Other stored (security) codesWhat are some of the common causes of the code?
Causes for this code may include:
Faulty PCM PCM programming error Open or shorted immobilizer lamp control circuit Defective (dead battery) immobilizer key (fob) Failed immobilizer lamp bulbWhat are some P0648 troubleshooting steps?
A diagnostic scanner, a digital volt/ohmmeter (DVOM), and a source of reliable vehicle information will be required to diagnose a code P0648.
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.
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. After recording all pertinent information, clear the codes and 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 more difficult to diagnose. The condition, which caused the P0648 to be stored, may need to worsen before an accurate diagnosis can be reached. If the code is reset, continue with your diagnosis.
Use your source of vehicle information to obtain connector face views, connector pin-out charts, component locators, wiring diagrams, and diagnostic flow charts related to the code and vehicle in question.
Check to see if there is battery voltage on the speed control warning lamp circuit by using the appropriate wiring diagram and your DVOM. If not check system fuses and relays and replace def
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