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 MANUALSMERCURY1998MOUNTAINEER 5.0 P, AWDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 14 (ANTI-THEFT SYSTEM - PASSIVE)SYSTEM TESTSDTC 1602: INVALID FORMAT KEY CODE FROM IGNITION KEY TRANSPONDER
1998 Mercury Mountaineer 5.0 P, AWD
DTC 1602: Invalid Format Key Code From Ignition Key Transponder
1998 Mercury Mountaineer 5.0 P, AWDSECTION DTC 1602: Invalid Format Key Code From Ignition Key Transponder
WARNING: This page is about a different car, the 1997 Ford Expedition. However, it is still accessible from the selected car via links, so may be relevant.
- Clear DTCs and rerun On-Demand Self-Test. See ON-DEMAND SELF-TEST in MODULE COMMUNICATIONS NETWORK article. If DTC B1602 is present, go to next step. If DTC B1602 is not present, system is operating properly.
- Using an existing and a new encoded key, program new key. See SPARE KEY PROGRAMMING under SERVICE PROCEDURES. Attempt to start engine. If THEFT indicator light turns on for 2 seconds and engine will start, replace damaged encoded key and retest system. If THEFT indicator light does not turn on for 2 seconds and engine will not start, go to next step.
- Set aside original encoded ignition keys. Using one new key, perform key initialization. See KEY INITIALIZATION under SERVICE PROCEDURES. Using newly encoded key, attempt to start engine. If engine starts, replace original encoded ignition key with newly programmed key. Program a spare key if necessary. See SPARE KEY PROGRAMMING under SERVICE PROCEDURES. Retest system. If engine will not start, clear DTCs and rerun On-Demand Self-Test. Repair as necessary. If no other DTCs are present except DTC B1602, replace PATS transceiver module and retest system.
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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.