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.
Code P051 & P108, Prom Checksum Mismatch
PCM PROM contains data essential in running engine and transaxle. Codes P051 and P108 checks the integrity of this data. RPM is divided into 2 halves or sides in the PROM. Code P051 checks one half of this data and Code P108 checks the other half. Integrity of this data is checked by adding up the data in all locations of the PROM, called the checksum. If checksum does not equal to what it should, code is set. The checksum is only checked when ignition is turned off and if it does not match, trouble code will set next time ignition is turned on.
Trouble codes can also be due to a bad connection between PCM and PROM, incorrect data in PCM due to electromagnetic discharge. Faulty PROM or internal PCM problem.
Ensure PROM is fully inserted in socket. If PROM is fully inserted, replace PROM. Clear memory and recheck. If Code P051 or P108 reappears, replace PCM.
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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.