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.
2006 Lincoln Navigator 4WD V8-5.4L VIN 5FACTORY OEM SERVICE PROCEDURE
Tests HF: Catalyst Efficiency Monitor and Exhaust Systems
PINPOINT TEST HF: CATALYST EFFICIENCY MONITOR AND EXHAUST SYSTEMS
WARNING: Crown Victoria Police Interceptor vehicles equipped with fire suppression system, refer to Section 419-03 for Important Safety Warnings. Failure to follow these instructions may result in personal injury.
This pinpoint test is intended to diagnose the following:
^ catalytic converter
^ exhaust system
Catalyst Efficiency Monitor Overview
Note: The HQ2S (A) and (B) locations may vary depending on exhaust system configuration. For additional information refer to Catalyst Efficiency Monitor and Catalyst and Exhaust Systems
The catalyst efficiency monitor uses pre and post-catalyst heated oxygen sensors (HO2S) to infer the hydrocarbon (HC) efficiency based on the oxygen storage capacity of the catalyst. Under normal closed-loop fuel conditions high efficiency catalysts have significant oxygen storage. This makes the switching frequency of the post-catalyst HO2S (B) very slow and reduces the amplitude of those switches as compared to the switching frequency and amplitude of the pre-catalyst HO2S (A). As catalyst efficiency deteriorates due to thermal and chemical detenoraUon its ability to store oxygen declines. The post-catalyst HO2S (B) signal begins to switch more rapidly with increasing amplitude approaching the switching frequency and amplitude of the pre-catalyst HO2S (A).
High Catalyst Efficiency
Reference:
Low Catalyst Efficiency
Reference:
HF1 - HF3:
HF4 - HF6:
HF7 - HF8:
HF9 - HF11:
HF12 - HF13:
Factory Service Tools
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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.
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