P048B: Volkswagen CJAA exhaust-flap position signal low

P048B identifies an exhaust-flap position-sensor circuit short-to-ground classification in Volkswagen's 2014 CJAA chart. Its malfunction criterion is signal voltage below 0.25 volts.

The measured position can become invalid

This row concerns the feedback signal, not a direct statement that the exhaust flap is physically closed. When the signal is electrically too low, interpreting the displayed position as actual flap movement can be misleading. The full diagnostic procedure must establish whether the feedback is credible.

The generic code title refers broadly to an exhaust-pressure control-valve position circuit. Volkswagen's chart supplies the more specific exhaust-flap context and the low-voltage classification for this application.

Different from position learning

The adjacent P048C entry checks the feedback during closed-position learning against a separate voltage range. P048B is the low electrical condition, while P048C concerns the learned-position plausibility test. The same visible flap behavior can therefore require different diagnostic evidence depending on the stored code.

Confirm the CJAA system before applying the 0.25-volt figure. The table does not identify the wire that is shorted, prove the sensor is defective or provide a motor test. Professional evaluation should preserve the distinction between the actuator circuit and its position feedback rather than replacing the exhaust-flap assembly automatically.

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