Home » OBD2 scanner not connecting to ECU (Fix OBD communication failure)

OBD2 scanner not connecting to ECU (Fix OBD communication failure)

Have you ever faced “No connection” issues with your OBD2 scanner? If the answer is yes, you assuredly know the pain it brings to you. Most of the cases, the scanner can connect to the ports and register error codes that result in a fault in the vehicle’s system. The OBD2 port is the one and only pathway where you can connect the OBD2 scanner. If you experience no connection between the two of these, you must know the actual faults in the OBD2 terminal. For the repair of this issue, you can go to the auto repair shops, but what if I share with you the real hacks to solve the issue at home. Okay, let us explore the innovative ideas to reconnect the OBD2 scanner with your vehicle.

OBD-II not connecting to ECU- What are the reasons and solutions?

There are several issues that the OBD2 scanner may not access the ECU or PCM. As the car comprises many parts, it could damage any of the parts, which may hamper the entire diagnosis system of the car. Let us check some of the common reasons that the scanner hesitates to connect with the ECU.

  • Compatibility problem of the Scanning tool 

In some cases, the OBD-II scanning tool is not compatible with the car or the vehicle. This problem is really common for cars. Some cars are made before 1996, and they show reluctance to connect with the OBD2 scanner as they do not have the system. The cars that are manufactured after 1996 are mostly compatible with the OBD2 system. So the first thing before connecting the tool with the car is you need to ensure that the vehicle is consistent with the ECU OBD2 system. problem scanning something went wrong Powered by

If you could find the compatibility, then check the inner side of the car’s engine or near the gearbox. You will find a sign that signifies that the car is compatible with the OBD2 system. There may also be the fact that you are using the wrong protocol, like the non-standardized OBD protocol such as ALDL, MOBD, MUTT, or OBD1, etc. There are manufacturer-specific protocols that cannot connect to the OBD2 protocol-supported vehicle.

  • The ignition key is facing discontinuation

The ignition system is one of the crucial elements of the car. If the ignition key is not connected with the car’s main interface or in the running position, then there is a chance that the OBD2 could not connect to the ECU (electronic control unit ). Some vehicles take a few minutes to complete the boot-up of the system. If you connect the scanner before the boot-up process, then there is a chance that the scanner won’t respond. Give the ignition some time to finish the restarting process. After the dashboard is cleared, you can connect the scanner, and you will notice the scanner in operation.

  • Low voltage problem with the connector

Low voltage must be the case for the connection failure of the scanner with the ECM. The OBD2 connector may be facing a common voltage problem, or the battery may encounter the same issues. Every device needs the power to operate, and the OBD2 scanner is no exception. It needs a minimum of 12-volt power to operate smoothly. If the voltage is lower than 12 volt, there might be some severe issues in the OBD2 connector. You need to appoint a voltmeter and take the readings to measure the voltage. Connect the red or the positive terminal to pin 16 and connect the negative side of the black side with pin four or pin 5. power supply low voltage problem

The fuse must be out of order if you can not find any volt between the pins. The fuse panel shares the DLC (Data Link connector) power with the accessory power. Then the main duty is to locate the fuse panel and check the blown fuse. Replace the fuse and again check the voltage power of the scanner. The OBD2 ports generally consist of 16 pin arrangements, and each pin is significant for connecting the scanner to the vehicle. Check the pins also if any of them is broken or torn. You can quickly terminate the low voltage problem by performing the above measures. 

  • ECM connection got interrupted

The ECM of the car is somehow called the brain of the vehicle. If the ECM faces any kind of inconvenience, then the entire system collapses. The ECM commands the other parts of the vehicle how to operate and when to operate. The regular checkings of the ECM are very much necessary as if they fail to operate, no other parts in the car would be sufficiently doing their operation. There is one effective solution to reboot the ECM to terminate the errors. For rebooting the ECM, you need first to disconnect both battery leads and accelerate the brakes to introduce any capacitor in the vehicle’s system. After a while, reconnect the battery again, and by that time, the entire ECM will be rebooted. To operate the entire process, you can follow the manufacturer-specific manual’s guidelines.  bad ecu ground symptoms

  • Showcasing invalid Data

Most of the scanning tools encounter quite the same problem, which is showcasing invalid data. The scanning tools connect the ECM of the vehicle and ask for valid PIDs. The main responsibility of the PIDs (Parameter Identification trigger function) is to give access to the powertrain control modules (PCM) information. An invalid PID information may ruin all the data, including the PCM reconnection to the other systems. In some cases, the PID showcases some invalid data, and the PID list could not be compatible with the main attributes of the vehicle.

Some of the OBD2 scanners can not automatically read the PID then. They seek help from the VIN (vehicle identification number) to figure out if the PIDs are valid. The VIN is a 17-digit attribute that determines a unique feature of the vehicle. To measure the data, if it is valid or invalid, the first step should be to examine the PIDs. If the PIDS are actual and compatible with the vehicle code, turn on checking the PCM for better results. 

  • Blown fuse problem

Whenever you plug in the OBD2 scanner with the vehicle’s main interface, it may not respond, and you have assumed that the main memory of the scanner may have died or gone out. But wait, it is not always imperative that the main memory of the car is out of order. There may have been some issues regarding the OBD2 scanner and ports fuse. A blown fuse is a common problem that the scanner may encounter. A fuse box is actually the component that protects the engine control module (ECM), cooling fan, ABS motor, battery, etc. There are several causes of a blown fuse, and the most dominant one is a short circuit in the electrical system. A short circuit may happen due to some significant causes like overheating or a high temperature that melts down the wires and connectors.

When there is an issue in the electricity supply between two conductors, the circuits face the worst of it. A blown fuse is always disturbing. Most vehicles have two fuse boxes in their system. A minor fuse problem impedes the OBD2 scanner from taking the absolute value and registering the error codes. So you need to check the fuse boxes and replace them if there is any fault. After repairing the fuses, you are ready to go with taking the actual values of the vehicle.             

  • Clogged incurred in the OBD2 port

The clogged port might be a severe issue for detecting the error codes. Actually, the port is the one and only medium for connecting the OBD2 scanner. If the port is blocked, you can not take the error codes. So be careful with your car’s port. Sometimes excessive dust is gathered in the internal pins of the port. Take a soft cloth and wipe the dust from the port. Careful not to use the wet cloth to clean the port. It is the ports that are the entrance for the scanner. So make sure that the port is always clean. Avoid using any kind of spray for the cleaning.  obd2 port not communicating

  • Fault in the CAN network

The CAN (Computer Area Network) is the internal organization that maintains the internal link between the computer networks. The CAN protocol is a well-organized framework compatible with the OEMs, Supplier design communication interface, and so on. The main system of the computer is called in so many names like the PCM (powertrain control module), ECM (Engine Control module), EBM (Electronic brake module), and many more. A severe fault in the CAN network might be hazardous for the entire vehicle system.

How to examine the OBD socket (DLC)?

Checking the OBD socket is one of the major strategies to figure out the problem in the OBD2 scanning procedure. The socket is mainly the 16-pin organization in the OBD2 port, and each of the port pins identifies individual values. The broken or damaged pins cannot circulate the information to the scanning device, which hampers the error codes’ overall detection process. The DLC is the main component that maintains the proper link with the CAN (Computer Area Network). To check the OBD2 socket, you need to follow some proper steps, and those steps are elaborated here, 

Firstly, perform a visual test of the sockets and the pins. All the DLC (diagnostic link connector) terminals are similar in look. So you may be confused when checking the terminals. You need to know the basics. The pins or the terminal numbers 6 and 14 are called the communication terminals, and they keep communicating with the vehicle’s CAN (Computer Area Network). The next thing that we will apply is the pin drag test. Apply a metal tool in between the pins conceptualizing the internal resistance of the pins and the terminals. If you feel fewer tensions in between the pins, then apply the basic tools to close the legs of the pins. That will increase the tensions in the pins. 


Why is the OBD2 not responding?

There are several factors behind the OBD2’s non-responding issues. One of them could be the damage to the cigarette lighter fuse. It is the part of the car which enables the smart devices to charge, and the standard value of the fuse is between 10 and 15 amp. A minor problem in this section is that the electrical wiring and the connectors may cause OBD2 communication discontinuation.

How does the DLC fuse work?

The DLC fuse is the vehicle’s multi-pin diagnosis system that produces valid live stream data and error codes. A blown-out fuse may hamper the overall system of diagnosing the OBD error codes.

How does OBD communicate?

The connection between the OBD2 scanner and OBD2 ports is the prime mechanism behind the registration of the DTC fault codes. The modern OBD implies the standardized digital communications port that provides fundamental data, and it makes the codes available to the screen of the scanner.

Hi, I am Henry, the owner of this website. If you are a DIY car enthusiast like me and are looking for an all-purpose OBD2 scanner, you’ve come to the right place. With 5+ years of experience in the automobile industry, I have in-depth knowledge about most of the OBD2 scanners regarding their software versions, firmware, features, updates, and compatibility. I love reviewing these gadgets after using and testing them personally. As a result, I always try to provide my honest opinion on the overall product quality.


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