If a 'HC hang-up' error occurs, which issue is most likely?

• A. A sample hose leak.
• B. A faulty catalytic converter.
• C. A misfired cylinder.
• D. Low battery voltage.

Answer: (A)

HC hang-up means the hydrocarbon reading is not settling properly because of an issue in the sampling path, not because of the engine’s combustion itself. The most likely cause is a leak in the sample hose. If the hose or its connections are leaking, ambient air can enter the sampling line or hydrocarbons can contaminate it, causing the analyzer to lose a stable sample and display a hang-up error. Replacing or resealing the sample hose and checking clamps and connectors typically clears this.

Other problems would affect the exhaust gas itself (like a catalytic converter not reducing HC or a misfiring cylinder increasing HC) rather than the sampling system’s ability to deliver a clean, stable sample. A low battery voltage could cause broader equipment failures, but it wouldn’t specifically present as an HC hang-up.