Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Circuit/System Verification
DTC P0633 will clear upon a successful engine start. Any malfunction that will cause a no-start condition will prevent DTC P0633 from clearing. Prior to diagnosing DTC P0633, ensure that all power moding and engine control systems are operating properly and all conditions that may cause a no-start have been corrected. Do not replace the K20 Engine Control Module. Replacing the K20 Engine Control Module will not correct the no-start condition.
- Verify there are no immobilizer DTCs set in the K9 Body Control Module.
- If any immobilizer DTCs are set in the K9 Body Control Module
Refer to Diagnostic Trouble Code (DTC) List - Vehicle .
- Go to next step: If no immobilizer DTCs are set in the K9 Body Control Module
- If any immobilizer DTCs are set in the K9 Body Control Module
- Perform the K45 Powertrain Control Module immobilizer learn using the powertrain control module IMMO Learn in SPS. Refer to Immobilizer System Component Programming .
- Verify the engine starts after the K45 Powertrain Control Module completes the learn procedure.
- If the engine does not start
An undiagnosed no-start condition exists. Refer to the appropriate subsection and diagnostic to correct the no-start condition.
- Go to next step: If the engine starts
- If the engine does not start
- All OK.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.