P048C: Volkswagen CJAA exhaust-flap closed-position learning

P048C is the exhaust-flap position-feedback plausibility entry in Volkswagen's 2014 CJAA chart. The manufacturer evaluates the signal during learning of the closed position.

The learning state is part of the criterion

Volkswagen lists feedback above 1.1 volts or below 0.5 volts during that closed-position learning. These values should not be applied to every normal flap position. A voltage observed while the flap is commanded elsewhere does not reproduce the condition described by the row.

This is a useful difference from P048B's signal-below-0.25-volt short-to-ground classification. P048C can concern a signal that is inappropriate for the learned closed position without necessarily matching that extreme electrical-low condition.

What a failed learning check leaves unresolved

The chart does not decide whether the reported position is wrong because of sensing, movement or another underlying defect. It also does not supply an adaptation-reset procedure or authorize forcing the flap against its stop.

Professional diagnosis should establish the correct CJAA actuator, confirm the requested learning state and evaluate the feedback with the complete workshop test information. The generic code title is broader than this manufacturer example. Treat the quoted limits as source-specific monitor criteria, not universal specifications for all exhaust-pressure control valves or a guarantee that replacement is required.

Source: Volkswagen manufacturer diagnostic chart, physical PDF page 42; physical PDF page 60.