P0633 Immobilizer Key Not Programmed – ECM/PCM

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


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 $154.99 . Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $50.0 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 $154.99 $50.0
Toyota $154.99 $50.0
BMW $164.99 $50.0

*Estimates may vary by market

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 $50 credit for the follow-up repair

Recent Check Engine Light is on Inspection reviews

Excellent Rating

(8600)

Rating Summary
8017
273
65
46
199
8017
273
65
46
199
 at YourMechanic

Brandon

9 years of experience
133 reviews
Brandon
9 years of experience
Ford Escort L4-2.0L - Check Engine Light is on - Nashville, Tennessee
Brandon showed up ahead of schedule, was very personable and diagnosed my problems. He also scheduled my next appointments which will be with him.
 at YourMechanic

William

23 years of experience
33 reviews
William
23 years of experience
Lexus IS250 V6-2.5L - Check Engine Light is on - Mableton, Georgia
Arrived early which was great. William was courteous, and attentive to the issue. Even though it took several attempts I'm so happy he was determined to fix it and he did!
 at YourMechanic

Dan

40 years of experience
1080 reviews
Dan
40 years of experience
Plymouth Grand Voyager - Check Engine Light is on - Lawrenceville, Georgia
Mr. Dan Barber was quite patient, courteous and quite knowledgeable. From my observation, Mr. Barber appears to be quite professional.
 at YourMechanic

Christopher

9 years of experience
120 reviews
Christopher
9 years of experience
Ford Fiesta L4-1.6L - Check Engine Light is on - Smyrna, Georgia
Chris communicated with us each step of the way up until his arrival. He listened well, was knowledgeable, and was prepared. He took the time to diagnose the problem, explained the what, why and how and provided a solution. I would definitely recommend him and will use him again.


More related articles

Related questions

Truck running rough
Hello. If this only occurs when the engine is cold then you may have a sensor reading incorrectly or you may have a vacuum leak. Most of the time if the Check Engine Light (https://www.yourmechanic.com/services/check-engine-light-is-on-inspection) is on I start by...
Where is the circuit one camshaft position sensor located?
Hello. The camshaft position sensor is located on the passenger side of the engine bay, on the cylinder head near the coolant reservoir tank. The reservoir tank needs to be removed in order to access it. If you need help...
My Check Engine Light is on - code P0025
Hi there. For your 2010 BMW, the [P0025 is the OBD-II error code] that (https://www.yourmechanic.com/article/p0025-obd-ii-trouble-code-camshaft-position-b-timing-over-retarded-bank-2-by-jay-safford) indicates the Engine Control Module (ECM) determines that the exhaust variable camshaft timing for bank 2 is more retarded than what the ECM desires. This...

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 (844) 997-3624 · hi@yourmechanic.com