Trouble code solution P0648: decoding, causes, resetting, meaning

Contents

Technical description and explained code P0648
Symptoms of vehicle malfunctions
Factors that can cause this error code
How to fix or reset OBD-2 code P0648
Diagnose and repair of problems
On which vehicles does this problem occur most frequently
Video

Fault code P0648 is called “Immobilizer Lamp Control Circuit Malfunction” but in different programs it may be called differently. This fault designation applies to all vehicles equipped with OBD-II.

Technical description and explained code P0648

OBD-II fault code P0648 is a general fault code that is most commonly defined as “immobilizer lamp control circuit fault”. It is set when the PCM detects a fault in the immobilizer lamp control circuit.

If your vehicle is equipped with a special security system, a microprocessor chip built into the key (immobilizer) is required to start the engine. Without it, if you turn the key to the start position, the engine will turn, but will not start. This is because the PCM will disable the fuel and ignition systems.

Thanks to the microchip and circuit board built into the key, it becomes a kind of transmitter. When the right key approaches the car, the electromagnetic field generated by the PCM activates the microprocessor and makes certain functions possible.

The immobilizer lamp is located on the instrument panel, its main function is to alert the driver that the immobilizer key is faulty or not recognized. This warning light is sometimes referred to as the immobilizer indicator light.

The PCM normally monitors the continuity of the immobilizer lamp control circuit each time the ignition is turned on. If a problem is detected while monitoring the immobilizer lamp control circuit. Then code P0648 will be stored and the malfunction indicator lamp (MIL) may illuminate.

Symptoms of vehicle malfunctions

The main signal that an error P0648 has occurred is the Malfunction Indicator Lamp (MIL) is also known as the CheckEngine Light.

It can also be warning signs such as:

The “Check engine” control lamp on the control panel will light up (the code will be stored as a fault).
The illuminated security warning light (immobilizer warning light) may or may not work.
The engine will not start.
In some cases, the engine may start but will shut off after two or three seconds.
The vehicle’s electrical system may be disabled if the maximum number of attempts to start the vehicle with an unrecognized key is exceeded.

Fault code P0648 should be classified as serious, because if it is present, you will most likely be unable to start the engine.

Factors that can cause this error code

The error code P0648 can mean that one or more of the following problems have occurred:

Faulty immobilizer lamp.
Open or short circuit in immobilizer indicator control circuit.
Faulty microprocessor key or keyfob.
Dead batteries in the key or key fob (the most common cause).
Defective ignition switch.
Damaged, burnt, shorted or corroded wiring in the CAN bus.
Sometimes the cause is a faulty PCM module.

How to fix or reset OBD-2 code P0648

Some suggested steps for troubleshooting and fix the error code P0648:

Read all data and stored error codes, using an OBD-II scan tool.
Clear the codes and check if error code P0648 appears again.
Test the immobilizer lamp and the circuit board on the instrument panel.
Check the batteries in the key or key fob.
Test the microprocessor key or key fob, it may be faulty and need to be replaced.
Inspect the wiring for damage.

Diagnose and repair of problems

When troubleshooting error P0648 it is best to start with a visual inspection of the relevant wiring and connectors as well as the key itself. If the key body has been cracked or damaged in any way, there is a good chance that the printed circuit board is also damaged.

It is not unreasonable to check the battery, as a weak battery can be the source of your problems. Weak or intermittent voltage in the electrical circuit can be directly related to the stored code.

Check to see if voltage is coming from the battery to the immobilizer check lamp circuit, using a proper wiring diagram and a multimeter. If there is no voltage, check the fuses and relays of the system, replace the defective parts if necessary.

If voltage is detected on the immobilizer control lamp, it is likely that the lamp is faulty and must be replaced.

Next, you need to connect the scanner to the diagnostic port of the car and save all the fault codes. You should start diagnosing and correcting the errors in the order in which they were saved.

A common cause of stored code P0648 is a dead battery inside the key. After its replacement this problem disappears. If the key itself is defective, after its replacement it will most likely require a reset procedure and training.