P1684 Code – Meaning, Causes & How To Fix It

Learn everything you need to know about the P1684 code in this post. Discover its meaning, common causes, and solutions to fix it

P1684 Code

Some trouble codes are considered generic and the meaning is the same for most types of vehicles. Other codes can be specific to the manufacturer, such as the P1684 code. If you have a Dodge, Jeep, Chrysler, Plymouth, Fiat or RAM, you want to know what this code means. 

In this guide, we look closer at the meaning of the P1684 trouble code and determine what fixes work out the best. We also touch on the symptoms, approximate repair cost and talk about how to diagnose the problem. 

Code P1684 Definition

P1684 – Battery Power To Module Disconnected

What Does the P1684 Code Mean?

The P1684 DTC indicates that the car battery was disconnected within the last 50 starts. The Powertrain Control Module (PCM) is responsible for monitoring the charging system and it sets this code when the battery was disconnected or there was a lack of voltage within the past 50 starts.

This code only applies to the Stellanis family of vehicles, such as Dodge, RAM, Chrysler, Jeep, Fiat and Plymouth models. While the code initially indicates that the battery was disconnected, there are other reasons for the code to be set. If you haven’t had the battery disconnected, you will need to perform some troubleshooting steps that we list in a few minutes. 

There are other manufacturers that use the same code, but the meaning is different. If you drive a vehicle that’s not part of the Dodge family, you want to research what those codes mean. We have a small list for you later in the article. 

What Are The Symptoms Of P1684?

If the battery was disconnected temporarily, you may only notice the Check Engine Light. If there are other symptoms present, there could be a larger issue occurring.

Here are some of the most common symptoms with the P1684 trouble code:

  • Check Engine Light
  • Computer memory loss
  • Erratic transmission shifting
  • Malfunctioning system sensors
  • Power system trouble
  • Electrical system glitches

What Are The Causes of P1684?

In many cases, the P1684 code appears because you disconnected the car battery at some point. Here are a few possible causes that you should consider.

How Serious is the P1684 Code?

Inspect Battery Terminal

Low – If you’ve just disconnected the battery, there’s probably nothing wrong. The code came on as a warning to let you know that the battery was disconnected. On the other hand, there could be something wrong if you haven’t disconnected the battery.

Depending on what could be wrong, you may need to take this condition more seriously. A bad battery or alternator could leave you stranded without any notice. 

How Do I Fix the P1684 Code?

If the code occurred because you disconnected the battery, it should reset automatically after 50 start-ups, but you probably don’t want to wait that long. In that case, you can simply reset the code with your compatible OBDII scanner. Otherwise, these fixes might be applicable.

  • Clean battery terminals
  • Tighten battery connections
  • Repair damaged wiring
  • Replace battery
  • Replace alternator
  • Update/replace PCM

Common P1684 Diagnosis Mistakes

Even as a professional mechanic, it can be tough to remember that not all trouble codes are universal. If you aren’t working with a vehicle from the Dodge/Chrysler family, this code may mean something completely different. For that reason, it’s important to research the trouble codes carefully. 

As an example, here is what the P1684 code means with some of the top automakers. 

  • Acura: Throttle Valve Return Spring Performance Problem
  • Buick: Transmission Control Module Power Up Temperature Sensor Performance
  • Cadillac: Transmission Control Module Power Up Temperature Sensor Performance
  • Chevrolet: Transmission Control Module Power Up Temperature Sensor Performance
  • Gm: Transmission Control Module Power Up Temperature Sensor Performance
  • Honda: Throttle valve – return spring performance problem
  • Mazda: Metering Oil Pump Position Sensor Circuit Malfunction

If you attempt to apply the same diagnostic steps and repairs to these vehicles, you will not resolve the issue. 

How to Diagnose the P1684 Trouble Code?

Diagnose Car 3

With some basic mechanical knowledge, you may be able to figure out what’s going on to cause the P1684 trouble code. Here are some suggestions and steps we would take as professionals.

  1. Read the trouble codes and research any others you find. If you notice another code that could be contributing to this problem, fix that one first. 
  2. If you recently replaced the battery, the PCM needs to be reset. Use your compatible code scanner to reset the codes and see if they come back. You could also wait until after 50 restarts for the car to reset on its own, but nobody really enjoys that route.
  3. If the code continues, you need to visually inspect the wiring. Fix any damaged wires, tighten the connections and clean off battery corrosion.
  4. Check the battery’s health and charge the battery fully. If the health is bad, replace the battery.
  5. If you haven’t figured out the problem, it’s time to get out the service manual. You want to follow the manufacturer-recommended methods for checking the battery, alternator and other charging system components. Many auto parts stores will also check the battery or alternator at no charge. Check online to see what’s available near you. 

Unless you are accustomed to working with the charging system, it may be better to leave this job to a professional. It’s not worth getting hurt over or frying the electronics because you are unsure of the proper protocols. 

How Much Does It Cost To Fix Code P1684?

For the most part, this problem is simple to fix on your own. For example, you should have no trouble tightening a connection or cleaning the battery terminals. For jobs that are more complicated, such as PCM replacement or update, you will need to visit a dealership or qualified service center. Here are some approximate repair costs you may deal with.

  • Clean battery terminals – $5 to $15
  • Tighten battery connections – $0 to $250
  • Repair damaged wiring – $25 to $550
  • Replace battery – $125 to $425
  • Replace alternator – $300 to $950
  • Update/replace PCM – $250 to $2,500

If you visually inspect the battery once a month, you can head off any problems with corrosion or disconnection.

A Mechanic’s Tips About The P1684 Code

In some cases, the P1684 trouble code can lead to damage to the CAN bus (Controller Area Network). This is a serious issue to find that shouldn’t be taken lightly. For this reason, we recommend investing in a professional code scanner if you plan to do your own work. The cheap scanners can’t read this system effectively.

If you aren’t willing to invest in a better scanner, it would be best to let a professional work on this trouble code. Additionally, if the CAN bus system is damaged, reach out to a mechanic. 

Is code P1684 serious?

It’s not a big deal if you’ve just disconnected the battery. The code will reset after 50 start-ups or you can manually reset it with your compatible scanner. If you didn’t disconnect the battery, the code may indicate something more serious wrong with the car’s charging system. 

How do I fix error code P1684?

It depends on what caused it. If you disconnected the battery, you simply need to reset the code. Otherwise, you need to go through some diagnostic steps to determine what’s wrong. You may need to fix a faulty connection or replace the battery or alternator, depending on what has failed. 

Can I drive with a P1684 code?

If you’ve just disconnected the battery, you are probably safe to drive. The code should reset after the car starts up for the 50th time. You can also reset the code with a compatible scanner. Otherwise, you should diagnose the problem and find out what’s wrong to determine if it is safe to drive or if a repair needs to happen sooner.

What Does An Internal ECM Failure Mean?

A complete ECM failure message would indicate that there’s no engine management for your vehicle. If this is the case, your vehicle may not start because it would be missing valuable inputs needed from the computer. The ECM may require an update or to be replaced, which is usually performed at the dealership. 

Conclusion

The trouble with the P1684 code is that the meaning of it depends heavily on what type of vehicle you drive. However, if you have a Dodge, Ram, Jeep or compatible vehicle, the meaning of it is pretty simple in most cases. It’s highly likely that you’ve disconnected the battery, either to replace it or clean it, and the computer recognized that it wasn’t connected. There’s nothing necessarily wrong that needs to be fixed.

However, there’s also the chance that you haven’t disconnected the battery, which would mean you have a problem to resolve. Follow our troubleshooting tips and repair the problem to get rid of the Check Engine Light and P1684 DTC. 

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