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P1684 Dodge OBD2 Code: Meaning, Symptoms, Causes, Diagnostics, And Fixes

Everything you should know about P1684 dodge

The P1684 is one of those OBD2 diagnostics trouble codes that won’t budge. Vehicles with this code will often have it recurring over time non-stop. The P1684 Dodge OBD2 code usually means that the battery is disconnected or that the electrical system’s power stayed lost within the last 50 starts.

The leading causes include a weak battery, replacing a car battery and its cables, faulty wiring around the PCM, CAN, and TCM.

The good news is that the problem usually goes away after a couple of start-up cycles. The bad news is that if the cause is a faulty component, it would require a mechanic trip since its diagnosis is complex to be fixed by an inexperienced person.

P1684 Dodge code definition: What does it mean?

Code definitions

The P1684 Dodge OBD2 code is defined as “Battery has been disconnected within the last 50 starts”.

Meaning of P1684

The P1684 DTC code is a manufacturer-specific code synonymous with Dodge, Chrysler, Jeep, and Mazda. Our focus will be on the P1684 Dodge OBD2 code – “Battery has been disconnected within the last 50 starts” since these codes differ between the given manufacturers. They have different definitions, diagnoses, and fixes. It is advisable to use your vehicle’s repair manual in conjunction with the procedures in this article if you are planning to fix it by yourself.

The code sets when the Engine Control Module (ECM)/ Powertrain Control Module (PCM) recognizes that the battery’s full voltage gets entirely lost during the last 50 cycles or that it became disconnected.

Any given scenario that results in the complete loss of full battery voltage can set this P1684 code. Another scenario that can cause this code to develop is the unavailability of battery voltage to any part of the electrical system or control module.

The P1684 code, in most cases, is typically stored when the PCM detects that the battery became disconnected in the last 50 start-up cycles or that the battery voltage had gotten completely lost in the previous 50 start-up cycles. A few cases may be due to defective or malfunctioning elements of the PCM, charging system, control module faults, corroded wiring.

Symptoms of code P1684

  1. An illuminated Check Engine Light/ Service Engine Soon warning.
  2. A stored Diagnostic Trouble Code (DTC).
  3. Loss of the Keep Alive Memory (KAM).
  4. The vehicle fails an emissions test.
  5. The faulty transmission does not shift correctly.

Causes of code P1684

  1. Disconnected battery or removed battery cables when the engine is still running.
  2. Low voltage in the battery.
  3. Faulty replaced or disconnected Transmission Control Module (TCM).
  4. Malfunctioning charging system.
  5. An open or shorted TCM harness.
  6. The faulty or poor electrical connection in the Transmission Control Module circuit.
  7. A weak battery.
  8. Poor electrical wiring around the Powertrain Control Module (PCM).
  9. Defective PCM.
  10. Poor battery terminal connections due to corrosion.
  11. Dysfunctional wires between the Controller Area Network (CAN) system and control modules.

How to diagnose and fix the code P1684

P1684 Dodge OBD2 code – “Battery has been disconnected within the last 50 starts”


Tip 1:

Make sure to always consult your vehicle model’s manual for the problem getting worked. The manual will be able to provide more detailed procedures that will help you fix this code. Different car brands will use P1684 for various issues, be sure to use the directions given for your specific car.

Tip 2:

Fix other codes that are thrown beside the P1684 first. Some of the codes may be generic or manufacturer-specific; pay attention to their specific definitions or their generic meanings. Take a look at their symptoms and figure out if they are due to the other codes or the P1684.

Tip 3:

In case the issue is caused by a faulty Controller Area Network (CAN) system, you will need professional-grade diagnostic equipment. Operating this equipment requires above-average diagnostic expertise. It is advisable to take this problem to a professional mechanic, or the least, refer to your car’s professional diagnostic procedures.

Tip 4:

The P1684 code will automatically reset itself sometimes or maybe get cleared off by the PCM. That will only happen if the code doesn’t reoccur within the 50 cycles proceeding with the previous process in which the code becomes sent. Allow your vehicle to run for at least 50 start-up cycles to see if the code gets cleared off automatically.

Tip 5:

You will need just one tool to perform the diagnosis and fixing procedures – an OBD2 scan tool.

Diagnosing & Fixing

Step 1:


Use the OBD2 scan tool to take note of all the codes stored by your PCM. Record all their definitions and refer to their meaning. That will help you in finding out which codes resulted in which to find the causal trouble code.


If other codes exist, fix them and then use the scan tool to rescan the system. The codes may be related to the P1684 if they don’t go away after performing their diagnosis and fixes. Please pay attention to the order in which they are stored and resolve them in the same order.

Proceed to the next step if the P1684 code persists.

Step 2:


Check the battery power to see if it is low on voltage. The battery will need a recharge if the voltage is low.


Make sure the battery gets recharged to complete to see if it is the cause of the problem. Remember that you may need to operate the vehicle for 50 start-up cycles before the code disappears.

Step 3:


Proceed to check for loose terminal and electrical wiring if the code remains. Diagnose the circuits and connections around the charging system, TCM, CAN, battery terminal, and PCM.


Fix any loose connections and replace any broken wires. Get rid of any corrosions or deposits near the systems and rescan to see if the code is still stored.

Step 4:


The code can persist until this point because of another underlying issue such as; a faulty PCM that needs to be reprogrammed or replaced. Another cause may be the 50 start-up cycles that haven’t been completed.

The latter is more probable since the PCM rarely fails.


Allow the vehicle to finish the 50 start-up cycles and see if the code is automatically reset. Rescan the system afterward to check if it is still present.

Step 5:


If the problem persists, then an intermittent fault exists. You will need a professional technician at this point since the troubleshooting of components such as the PCM and CAN are challenging to do.


The mechanic will then refer to the vehicle’s manual and use his/her expertise to fix the issue.

Other codes related to code P1684

P1684 Dodge OBD2 code does not have any other manufacturer-specific codes that are directly related to it. Some vehicles may throw generic codes besides the P1684, but they are major due to the P1684 code rather than its cause.

Tips to avoid code P1684 in the future

It is not advisable to disconnect the battery unless the vehicle’s manual specifies so. Some professional mechanics and car owners disconnect the negative battery terminal to perform a computer reset. This procedure gets used to reset the computer by disconnecting it from the power source. The process should rarely get used unless otherwise stated.

The tip for you here is to make sure your battery or battery cables aren’t disconnected unless it is necessary.

Outro/Final Thoughts/To Sum Up

P1684 Dodge code, on its own, does not cause any drivability issues to the vehicle. However, if the code gets set by disconnecting the battery when the engine was still running, or the ignition was still on, then the code will damage the car’s electrical system. You do not want to drive a vehicle with severe electrical issues.

In the majority of the cases, the code will automatically reset over time without any concerning issues. Be sure to let the vehicle finish the needed cycles before taking it for a check-up.

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