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.
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HOMESERVICE MANUALSMAZDA1999626 ES, 2.5 D, STANDARDREPAIR AND DIAGNOSIS (SINGLE PAGE)ACCESSORIES & EQUIPMENTANTI-THEFT SYSTEMSIMMOBILIZER SYSTEMSDIAGNOSTICS TESTSDTC P1621: CODE WORD DOES NOT MATCH AFTER ENGINE CRANKING
1999 Mazda 626 ES, 2.5 D, Standard
DTC P1621: Code Word Does Not Match After Engine Cranking
1999 Mazda 626 ES, 2.5 D, StandardSECTION DTC P1621: Code Word Does Not Match After Engine Cranking
- Using NGS tester, clear DTCs. See CLEARING DTCS . If same DTCs are present after cranking, go to next step. If different DTCs are present, repair appropriate DTC first. If no DTCs are present, repair is complete.
- If NGS tester displays DTC P1602, go to DTC 1602: IMMOBILIZER UNIT - PCM COMMUNICATION ERROR . If NGS tester does not display DTC P1602, replace immobilizer unit and reprogram, go to next step. See IMMOBILIZER UNIT under REMOVAL & INSTALLATION. After component replacement, see IMMOBILIZER UNIT under PROGRAMMING.
- Attempt to start engine. If engine starts, repair is complete. If engine does not start, replace PCM and reprogram. See POWERTRAIN CONTROL MODULE under REMOVAL & INSTALLATION. After PCM replacement, see POWERTRAIN CONTROL MODULE under PROGRAMMING.
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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.