P1604 code — how to fix error fast

If the code P1604 appears in your car it can be a sign that something is off when it comes to the communication between the car’s vital modules. Not only does this mean that the operation of the key systems like the transmission or powertrain can be compromised, but it also leads to a series of other issues.

That’s why our team made a comprehensive guide on the P1604 code meaning, why it happens, and how to fix it. We won’t waste any of your time, so let’s get straight to the business and explain the code in a bit more detail.

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What does the P1604 code mean?

The P1604 code is a generic powertrain code that indicates a malfunction in the engine control module (ECM) or transmission control module (TCM) communication circuit. This code is important because it can affect the performance of the vehicle and may cause further damage if left unaddressed.

In this article, we’ll provide an overview of what the P1604 code means, the potential causes of the code, which car models are most affected, how to diagnose the code, how to fix the code, and how to prevent the code from occurring in the future.

What causes the P1604 code?

The code P1604 can be caused by a variety of issues, and the main symptoms behind the code confirm it. You may recognize a change in your car’s fuel economy, engine performance, and transmission (mostly through rough gear shifts), while the “check engine” light may also appear on the dash.

So, the code can be tracked down to these few reasons that may trigger such symptoms:

Faulty ECM or TCM

A faulty ECM or TCM can cause the P1604 code to appear. This can occur due to a manufacturing defect, damage to the module, or wear and tear over time.

Wiring issues

Wiring issues can also cause the P1604 code to appear. This can include damaged or corroded wires, loose connections, or wiring that have been improperly installed.

Sensor issues

Sensor issues can also cause the P1604 code to appear. This can include faulty sensors, sensors that have been incorrectly installed, or sensors that have become damaged over time.

Which car models does the P1604 code affect the most?

Due to the general nature of the issue, the code P1604 can appear in almost any car, especially those with older and outdated ECMs. However, we’ve come across a few vehicles models that are said to be more prone to this issue than others, so here’s what it all looks like:

• Toyota Camry: These cars use a lot of electronic systems that may cause communication errors between the ICM and ECM.
• Nissan Sentra: This vehicle model has multiple electronic modules that need to communicate with one another, and a problem with any one of them can cause the P1604 error code.
• Mitsubishi Outlander: These cars have complex electronic systems that may require significant troubleshooting in order to resolve the issue.

How to diagnose the P1604 code

Diagnosing the code P1604 can be tiresome if you don’t know what you are doing, so our team wanted to make the task easier for you. We’ve come across a few quite effective ways of diagnosing the code, so you can apply these methods when trying to configure the nature of the problem:

Check for other DTCs

Before diagnosing the P1604 code, it’s important to check for other DTCs that may be present. This can help identify any underlying issues that may be contributing to the code.

Check the ECM and TCM

The next step is to check the ECM and TCM for any visible damage or defects. This can include looking for broken wires, damaged connectors, or corrosion.

Check the wiring

If the ECM and TCM appear to be in good condition, the next step is to check the wiring between the two modules. This can include checking for loose connections, damaged wires, or improper installation.

Check the sensors

If the wiring appears to be in good condition, the next step is to check the sensors that are connected to the ECM and TCM. This can include checking for damaged sensors, incorrectly installed sensors or sensors that have become corroded over time.

How to fix the P1604 code

Based on what you’ve found through the diagnostic phase, there are various ways of fixing the code. So, you can make use of these options to figure out a solution for the code and hopefully erase it:

Replace the ECM or TCM

If the ECM or TCM is faulty, it may need to be replaced. This can be an expensive repair, but it is often necessary to fix the P1604 code.

Repair the wiring

If the wiring is damaged or improperly installed, it may need to be repaired or replaced. This can involve splicing new wires, replacing connectors, or re-routing the wiring.

Replace the sensors

If the sensors are damaged or improperly installed, they may need to be replaced. This can involve purchasing new sensors and installing them correctly.

How to prevent the P1604 code

Preventing the P1604 code involves regular maintenance and care of the affected systems. This can include:

• Regularly checking the wiring and connectors for signs of damage
• Replacing damaged sensors or wiring
• Performing routine maintenance on the ECM and TCM

By following these preventative measures, drivers can reduce the likelihood of the P1604 code appearing on their vehicles.

Our take

Ultimately, the code P1604 can be pretty bad if it leads to a complete stall in communication between the ECM and the TCM, as it can therefore affect the drivability of your car. However, if you manage to deal with the code on time, you likely won’t have to deal with the lack of communication and therefore preserve your car’s vital systems.

In that sense, this guide may serve you well on the road to keep the systems safe and sound while never having to deal with more expensive repairs like replacing the ECM or TCM.