P0633 Immobilizer Key Not Programmed – ECM/PCM

Our certified mechanics come to you · Get a fair and transparent estimate upfront

Red-stars EXCELLENT RATING ON

Cost of diagnosing the P0633 code

P0633 is a diagnostic trouble code (DTC) for "Immobilizer Key Not Programmed – ECM/PCM". This can happen for multiple reasons and a mechanic needs to diagnose the specific cause for this code to be triggered in your situation. Our certified mobile mechanics can come to your home or office to perform the Check Engine Light diagnostic for $114.99 . Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $20.0 off as a credit towards the repair. All our repairs are backed by our 12-month / 12,000-mile warranty.

Cars Estimate Credit towards follow-up repair Earliest Availability
Ford $114.99 $20.0
Toyota $114.99 $20.0
BMW $124.99 $20.0
SCHEDULE P0633 DIAGNOSTIC Get a fair and transparent estimate upfront

P0633 code definition

The P0633 code is triggered when the vehicle's PCM (Powertrain Control Module) or ECM (Engine Control Module) is unable to recognize the immobilizer key.

What the P0633 code means

P0633 is cued when there is an internal malfunction or improper programming resulting in the PCM being unable to recognize the immobilizer key. The immobilizer is an engine component that prevents it from running without the proper electronic immobilizer key. The code indicates that the vehicle will not start because the proper key is not in use.

What causes the P0633 code?

This code is most commonly caused by the following:

  • The PCM has been recently replaced but did not receive the programming required to match the vehicle and/or immobilizer key.
  • A fault in the PCM.
  • A defective ignition cylinder.
  • Open or shorted connectors or wiring.
  • A defective immobilizer key.
  • A dead battery that is discharged for a lengthy period of time can cause the PCM to lose its programming, and the need for a reprogramming can be the cause of this code.

What are the symptoms of the P0633 code?

P0633 code typically cues the vehicle to illuminate a security lamp or key indicator that signals a "no start" will occur.

How does a mechanic diagnose the P0633 code?

The P0633 is diagnosed with an OBD-II scanner, but the use of a digital volt/ohmmeter is also important in properly diagnosing this issue. The standard protocol begins with a visual inspection of the vehicle's wiring. Any problematic issues must be addressed, including replacing or repairing shorted, disconnected, damaged or corroded wires and connections. Components and fuses in need of repair or replacement are addressed at this time too.

The system is then re-tested and if the wiring is functioning properly, the mechanic may then connect the OBD-II scanner to the vehicle's diagnostic connection and document the codes and freeze frame data it contains. It is important to note any data or irregular issues that may have played a role in the code storage. Clear the code and attempt to operate the vehicle as this can indicate if that is the source of the problem. If it is not an electrical or wiring issue, it is likely that the PCM will need diagnosis and/or replacement. Typically this is more complex and requires the use of an Autohex or specialized scanner.

A mechanic must also assess any recent repairs, as any changes in a control module may lead to a reprogramming-related problem, and the P0633 code. It may also be necessary to use an auxiliary immobilizer key to test the current key's authority. If none of these yield results, the final test to perform is on the ignition cylinders as some vehicle types trigger this code when a cylinder is defective.

Common mistakes when diagnosing the P0633 code

This is a very rare code with a very narrow number of causes. There are rarely misdiagnosis or mistakes to be made when this code is triggered.

How serious is the P0633 code?

This is a very serious issue because it prevents the vehicle from starting. Though helpful in the prevention of "hot wiring" and auto theft, when it is a malfunction in the immobilizer key or the PCM/ECM it locks down the engine and prevents the vehicle from operating at all. Unfortunately, diagnosis and resetting the codes is not always going to address the problem because reprogramming may be required. The vehicle ID, mileage, and any anti-theft settings may need to be reset before the vehicle can be operated.

What repairs can fix the P0633 code?

The most common repairs required for the P0633 code are:

  • Verifying with code reader or scanner, and clearing the code to see if the issue returns.
  • Determining if there was intermittent issue that triggered the code, such as an electrical issue. This is why diagnosis also requires visually inspecting all of the connections and repairing or replacing wiring, connections, components and fuses before retesting.
  • A PCM or another control module, ECM for example, may need to be replaced and then reprogrammed to match the vehicle.
  • The use of an auxiliary immobilizer key may be necessary to gauge the key's authenticity and to reprogram any new control modules properly.
  • Repairing this issue can also mean assessing and repairing defective cylinders in the ignition.

Additional comments for consideration regarding the P0633 code

Never replace a PCM with a used component as this will not alleviate this issue. The OBD systems can function exclusively in the one vehicle, programming everything into the PCM or ECM, and then relaying and sharing information with other control modules through the CAN bus network. This code can mean a new PCM/ECM and that means reprogramming the unit to match the vehicle.

Need help with a P0633 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

Check Engine Light
trouble codes
P0633

No more waiting rooms! Our mechanics will come to you to diagnose and fix the P0633 code.

SCHEDULE P0633 DIAGNOSTIC
Get a $20 credit for the follow-up repair

Recent Check Engine Light is on Inspection reviews

Excellent Rating

(7294)

Rating Summary
6779
246
57
39
173
6779
246
57
39
173
 at YourMechanic

Simon

30 years of experience
8 reviews
Simon
30 years of experience
Honda Element L4-2.4L - Check Engine Light is on Inspection - Albuquerque, New Mexico
Simon was Professional, knowledgeable and patient throughout the entire process. Would highly recommend!
 at YourMechanic

Luke

17 years of experience
134 reviews
Luke
17 years of experience
Chevrolet Equinox L4-2.4L - Check Engine Light is on - Austin, Texas
Luke was friendly and professional. He did a nice job of explaining the issue with my car so that I could understand it.
 at YourMechanic

Chuy

14 years of experience
386 reviews
Chuy
14 years of experience
Toyota Camry L4-2.5L - Check Engine Light is on - Chicago, Illinois
His explained everything very clearly on what I should do next with my car and what the cheapest solutions were.
 at YourMechanic

Jose

12 years of experience
31 reviews
Jose
12 years of experience
Chrysler Pacifica V6-3.8L - Check Engine Light is on - Redlands, California
Very friendly and punctual. Knows what he is talking about. Appreciate Jose working on my car. I would recommend him to customers.


More related articles

Related questions

Car dies after charging battery

The symptoms described for your Mitsubishi Outlander lead me to believe you are dealing with a weak battery. As batteries age, they lose the ability to hold a charge. The Check Engine Light could be on as a result of...

Bmw 2005. e90 320i N46, have cel on, code is p0013. Engine is stalling, consumption is higher. What do you suggest?

Hello. P0013 (https://www.yourmechanic.com/article/-p0013-obd-ii-trouble-code-b-camshaft-position-open-or-short-in-oil-control-valve-ocv-bank-1-by-jay-safford) is the code for a malfunction of Camshaft Position Actuator Circuit B (Bank 1). It may be possible that there is an issue with the cam actuator or the Vanos oil control solenoid. If either of those...

2002 duramax went into limp mode after fluid ad filter change

Hello, I can help you with this! When doing a transmission service for this vehicle, you will set a (DTC) trouble code for a low pressure condition with transmission. This is a normal condition when replacing the filter and...

How can we help?

Our service team is available 7 days a week, Monday - Friday from 6 AM to 5 PM PST, Saturday - Sunday 7 AM - 4 PM PST.

1 (855) 347-2779 · hi@yourmechanic.com