Obd2 Not Connected To ECU – How to solve?

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When OBD2 is not connected to the ECU, it doesn’t necessarily mean it’s incompatible. Typically, the program is set up to automatically test all of the connection protocols in the same order. As a result, the device may get stuck in an endless cycle of connecting attempts to the wrong protocol. Indicators on the dashboard will frequently become useless when this occurs.

This isn’t a foolproof option, as the car may not be suitable, but why not give it a shot to solve the problems. In order to proceed, one must first determine whether the OBD2 protocol is correct for the vehicle in question. We may easily find out by searching the database of automobiles that are compatible with it. Let’s learn more about the reasons and how to solve them.  

Common OBD2 Problems

If you get no OBD code, the most typical cause is a blown fuse, ECMs (also known as engine control units, electronic control units (ECU), or powertrain control modules (PCM), on many cars, share the same fuse circuit with other electrical ports, like multimedia ports and other sockets. 

The scan port may have grown clogged with dust over the years due to lack of use, which is another possible explanation for the lack of reading. Use a soft cloth or a can of compressed air instead of a spray cleaner to clear the port of any debris that might be interfering with your scan tool’s ability to receive an accurate reading.

Is It Possible To Solve OBD2 Not Connected to ECU Problems?

When your scan tool does not work when plugged into the OBD port of your car, there’s a general assumption that it’s either not compatible or simply won’t connect. Except it’s about compatibility problems, then yes, the OBD2-ECU connection is solvable for sure.

You can, however, check out our detailed instructions below on how to fix an OBD2 Scanner for Prado that won’t even turn on when you plug it in. Many times, a scan tool won’t power up because the fuse has blown

Why OBD2 Not Connected to ECU

There are different reasons why your OBD2 is not connected to ECU so you won’t be able to retrieve and reset DLCs. These include but aren’t limited to:

  • Incompatible scan tool (Use a professional scanner)
  • Blown fuse
  • Corrosive pin
  • Worn socket/pin
  • Dirty connectors
  • CAN network fault
  • Wear and tear on connectors
  • Broken scan tool

What To Do When OBD2 is Not Connected to ECU

Check the pins on your scan tool plug. Sixteen pins are used for the OBD2 scanner and the port. Look for pins that are bent or forced or worn that prevent it from having good contact with the socket. 

For a quick check, connecting your scan tools to another car and seeing if they work is a quick and easy approach to verify their functionality. Another possibility is that your vehicle’s OBD terminals may have an issue so you would need more rigid solutions.

Watch this video

Obd2 Not Connected To ECU – How to solve?


Make sure the plug is clean and free of rust or other dirt. Check both the cord and the scanner’s plug for damage. A faulty cable, socket, plug, or pin is a simple problem to resolve. The OBD cable is usually detachable and interchangeable in good scanners. Purchase a replacement cable right now. They don’t cost a lot but would straightforwardly solve your problems.

How To Solve OBD2 Not Connected to ECU

Solve OBD2 Not Connected to ECU

Assuming that you have the Best Autel Scanner compatible with your vehicle, then problems might be related to the scan tool plug, OBD socket, or CAN network. You can try our guide to solve one of these problems below.

1. Solutions for Scan Tool Plug Problems

Before anything else, you can check the scan tool plug as we’ve explained above. The corrosive connector or bent pin may cause faulty connections that prevent your scan tool from having good contact with the OBD port in your car. If this doesn’t solve your problems, then you can move to the OBD socket itself.

2. Solutions for OBD Socket Problems

It’s a little bit tedious to check your vehicle’s socket, but certainly worth your effort. It is possible that a visual test will uncover the socket problem. However, you will need to perform a pin drag test if the connection problem still persists.

Female terminals are the DLC connectors on your car. The terminal legs can possibly lose tension as a result of extensive use and probing that’s fronted. These cause resistance from the socket itself which typically causes the communication problem between  OBD2 and your car’s ECU. 

3. Solutions for CAN Network Problems

As you might have known, control modules are increasingly being used in modern automotive electrical systems. Several might be employed in your car. A controller is a control module that is part of a larger system. 

The computers in automobiles go by many different terms, and some manufacturers even come up with their own. But don’t worry about it; they’re all simply module controllers. When you have CAN  problems, there are chances your OBD2 won’t be connecting to the ECU. 

To check whether or not the CAN network is the root cause of your OBD2-ECU connection, you can try the following solutions:

  • Check CAN Voltage
  • Check CAN compatibility
  • Repair CAN Network
  • CAN Voltage drop Ground Test
  • Test CAN resistance


Can the OBD2 scanner damage the ECU?

It’s possible that the ECU was “electrocuted to death”. The OBDII interface is capable of implementing a variety of data bus voltages. Bus lines could be damaged by being connected to a higher voltage than 12V. 

CAN OBD2 reset ECU?

For the most part, the OBD Scanner is used to gather information about the car’s performance, analyze data from the engine, transmission, safety, or other systems and identify potential problems. Generic OBD Scanners are not capable of resetting the ECU but some advanced scanners have this capability. 

How do I reset my ECU manually?

When you’re reconnecting or replacing the ECU fuse, you’re basically resetting your ECU manually. Another way is to use the scan tool with the capability of resetting the ECU of your car.

What is OBD communication failure?

the OBD-related tool will not work if the fuse has been blown which leads to communication failure. It means that the OBD scan tool can communicate with your car. While the blown fuse is the common cause, this communication failure can also be caused by incompatibility, faulty CAN, corrosions, etc.


There are apparently different factors that may cause the connection failure between OBD2 and ECU. You must check the root cause to apply the correct troubleshoot where you might have to visually observe the connectors or perform a CAN test. It’s very important to purchase only compatible scan tools for your car.

OBD2 not connecting to ECU easy fix |Why Won't My OBD2 Scanner Connect to My Car?
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