7 Reasons For Dodge Cummins P0633 Code And Quick Fix

You probably panic when you can’t start your car and then the P0633 code comes up in your OBD II scan. It can be really frustrating first thing in the morning but don’t worry, we have all the possible solutions.

First, let’s see what P0633 Code Dodge Cummins means.

P0633 code in Dodge Cummins means your ECM (Engine Control Module) or PCM (Powertrain Control Module) is facing an immobilizer key that it does not recognize. This can happen when there are battery issues,  programming faults, faulty keys, defective ECM, or PCM systems. Reprogramming or replacing affected components will solve the issue. 

We have specific fixes for every one of those issues. Read on to find out which one applies to your Dodge Cummins. 

What Does P0633 Code Mean?

Dodge Cummins P0633 Code

You are unable to start your car and the OBD II shows the P0633 code. To understand the reason behind this, we need to understand the relationship between your car and your car key fob.

When using your car key to unlock the door and start the engine, a signal is transmitted from your vehicle key. When this signal information matches with what the reader (your car) is programmed to accept, then your car starts.

There is an immobilizer key and transponder in your key fob that protects the vehicle from theft. The immobilizer key sends a unique transponder signal to the vehicle. Onboard controllers need to recognize this signal to start the engine and unlock doors and trunks.

When there is any issue that deters this communication between the control modules (ECM, PCM, BCM) and the immobilizer key, the P0633 code will appear.

Do You Need To Fix The P0633 Code Immediately?

Yes, if you have a P0633 code on your Dodge Cummins, you need to fix it immediately. It is a serious issue since you can’t start your engine or get inside your car when you have this error code.

Usually, the engine check light will appear and after the OBD II scan, you get this code. After that, you should not delay in your fix.

7 Possible Reasons And Solutions To P0633 Dodge Cummins No Start

Reason Symptoms Solutions
Dead Battery Car engine won’t start Reprogram PCM
Wiring IssuesVisible loose wiresFix the Wiring 
Key Low On Battery Battery LED light off or Need to be Closer to the car to turn on. Replace Battery 
Defective Immobilizer Key Key fob doesn’t work Get A New Key 
Key Replaced Without Re-Programming Key fob doesn’t work Reprogram Key Fob 
ECM/ PCM Programming Error Key fob doesn’t work Reprogram PCM
Faulty PCM Key fob doesn’t work Replace PCM 

There are seven possible reasons for the P0633 code to appear. All of them stem from lost communication with PCM. 

Reason 1: Dead Battery

When you have a dead battery for a long time, automatically your PCM might lose all its programs. As a result, it won’t be able to call back its memory when the key fob sends a signal.

Since PCM can’t identify the signal it will show this error code. 


You won’t be able to turn on your car if you have a dead battery. 

Solution: Reprogram the PCM

Re-programming the PCM will solve this issue. Now you might be wondering how do I reprogram my PCM.

Usually, it is recommended to reprogram PCM at a dealership. However, if you want to do it on your own, follow the below process.

Tools Required 

  • PCM Scanner 
  • PCM software
  • Computer

To get the exact PCM scan tool and software, contact your local dealer.


  1. Download the PCM software on your computer. 
  2. Connect the scan tool to your computer
  3. Make sure your battery is fully charged. Start the software program and enter your vehicle information. You might need your vehicle’s VIN number as well. 
  4. After the data is transferred to the scanner, disconnect the scan tool. 
  5. Locate your car’s PCM. Usually, it can be found near the battery. 
  6. Find the OBD II connector on PCM and connect it with the scan tool. 
  7. Start your car ignition. 
  8. Turn the scan tool “ON”.
  9. Key-in vehicle information and start the transfer
  10. The scan tool will alert when the transfer is complete
  11. Disconnect the scan tool from the OBD II connector 
  12. Turn off your car’s engine
  13. Start the car again to check if the engine check light is still on or not. 

Maintenance Guide

  • Do not unplug your battery for more than 30 mins. 
  • Make sure your headlights are off when the engine is turned off.
  • Check if the alternator is working properly. 
  • Stay away from extreme temperatures. 

Reason 2: Wiring Issues

Loose, damaged wires in your key fob or PCM will disrupt the connection between the immobilizer and the vehicle. Consequently, the P0633 error code will appear.


Check for loose wires with a visual inspection. Check both your key fob and PCM unit. 

Solution: Fix Wiring

Steps to fix loose or damaged wire are as below.

  1. Open the bonnet of your vehicle. 
  2. Locate the PCM. You can find it in the engine compartment, on the right side of the firewall.
  3. There should be a few plugs there and lots of different colored wires.
  4. See if any of the plugs are loose. If yes, push on the plugs to tighten them. 
  5. If any wires are damaged, clean the damaged area and cover it with liquid electrical tape. After it is dried, rewrap it with tape again. 

Maintenance Guide

Regularly check PCM connections for loose wires.

Reason 3: Key on Low Battery

Usually, your key fob has a non-rechargeable 3 Volt battery. It runs on average for 3 years without replacement. It can run low on battery and cause the code to show up.


If your key fob battery is running low, you will have to be closer to your car to make it work. Also, your LED light on a key will be off if the battery is dead. 

Solution: Replace the Battery

Steps to replace the battery with a new one is given below.

  1. Buy a new key fob battery. It is circular in shape and looks like a watch battery. 
  2. There is a small button on the side of your key fob. Push that button and a key will pop out.
  3. Use that key to get the cover off your key fob and you will see the circular battery.
  4. Take out the battery by pressing the key under it and put the new battery in.
  5. Put the battery in a way that the logo side is facing down.
  6. Put the cover back on and slide in the key inside the fob. 

Maintenance Guide

Track how long you have been using a car key battery. Replace the battery every 3 years. 

Reason 4: Defective Immobilizer Key

A defective transponder chip causes an immobilizer key to be flawed. You won’t be able to connect with the vehicle control module if that is the case. Consequently, you will get the P0633 code. 

Solution: Get A New Key

A broken transponder chip is very expensive to replace. So, it is better to contact your local dealership to get a new key.  A new key fob can be from $50 to $400, and programming costs an extra $50 to $100.

Maintenance Guide

Don’t drop your key on hard surfaces. Keep your key away from water. 

Reason 5: Key Replaced Without Re-programming

When you have changed your key fob but haven’t programmed it to match your car’s control module the P06333 will appear. 

Solution: Reprogram Key Fob

Re-program your key fob after replacement. It is an easy process and you can do it yourself.

The process below will explain how to reprogram your key fob.


Remember you have to be quick to follow these steps. 

  1. Get your key fob and get inside your car. Close all doors. 
  2. Turn the key to the “ON” position to turn the ignition on
  3. Press your fobs’ Lock button
  4. Turn the ignition key to “OFF”
  5. Repeat steps 2-4, three times. 
  6. Turn the ignition key back “ON” and you will hear a lock sound
  7. Turn the ignition key “OFF”
  8. Test the key fob once you are outside of your car

Maintenance Guide

Use a key fob cover to protect from damage. Use a wallet for a key fob to protect from hackers. Don’t forget to reprogram after you have bought a new key. 

Reason 6: ECM/ PCM Programming Error

If you have recently replaced your ECM or PCM then you need to reprogram it. Otherwise, these control modules won’t be able to communicate with the key fob. 

Solution: Reprogram the PCM

You need to reprogram ECM/PCM. The process to reprogram the PCM has already been discussed above. You can follow the methods to solve this issue.

Maintenance Guide

If you have replaced any component connected to the PCM, you must reprogram your PCM. 

Reason 7: Faulty PCM

The following symptoms indicate a faulty PCM. A faulty PCM won’t be able to receive a signal from the key fob. Hence, it will show the P0633 code.

So, what is the most common failure of a PCM?

The most common failure of PCM is usually due to voltage overload or environmental factors. So, make sure your solenoid and actuator circuit is in proper condition. At the same time, to protect it from corrosion, make sure water doesn’t get inside the PCM.

The Signs Of A Failing PCM: 

  1. Increased fuel consumption  
  2. Excessive emission 
  3. Check engine light on 
  4. Rough start or Can’t start the engine at all
  5. Engine stalling and misfiring 
  6. Inconsistent shifting in your transmission 

Solution: Replace PCM

If you have a faulty PCM, you need to replace it. It usually costs $500- $1500 and the labor cost is around $120. 

It is possible to replace PCM by yourself with the help of a few tools.

Tools Needed 

  • Ratchet set 
  • Socket set 
  • Screwdriver 


  1. Disconnect the battery terminals and wait for 30 mins
  2. Remove the air intake near the PCM 
  3. Use a socket to remove the PCM 
  4. Pull all plugs out from PCM by applying pressure on the top and bottom 
  5. Bolt the new PCM on 
  6. Bolt the air intake back 
  7. Reconnect the battery terminals 
  8. Start the Vehicle

Maintenance Guide

Don’t operate your engine in extreme temperatures. Check for loose or shortened connections regularly.

The P0633 code on Dodge Cummins has very specific reasons and solutions. After going through these 7 reasons and solutions, the P0633 code issue should be resolved.

Read More-

  1. P0107 Code Dodge Cummins – Causes, Symptoms, & Solution
  2. Causes of P2459 Code 6.7 Cummins with Solutions


What is SKIM on PCM?

SKIM is the Sentry Key Immobilizer Module on PCM. Its purpose is to stop any unauthorized key from trying to start the vehicle by disabling the engine. You can buy a program that deletes the SKIM from your PCM. 

Do you have to reprogram a key fob after changing the battery?

Yes. It is recommended to reprogram the key fob after changing the battery. It takes only a few minutes to reprogram and you can do it on your own. 

Can You Delete The Immobilizer?

Yes. You can delete the immobilizer. It is also known as immo bypass and it allows the control module to ignore the immobilizer.

Bottom Line

Even though p0633 code dodge Cummins shows up for several reasons, I hope this article helped you to identify the causes. At the same time, with our helpful guide, we hope you were able to diagnose and fix the problem properly. 

Make sure to properly maintain your vehicle so that you can avoid the issues. This is it for today. Leave us a comment to let us know your feedback.

Bye for now!


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