P240B: Volkswagen leak-detection pump heater control low

P240B is the low electrical classification for the leak-detection pump heater-control circuit in Volkswagen's 2014 CBTA/CBUA chart. It should be kept distinct from the pump motor's own control-circuit faults.

The voltage criterion is calibration-bounded

Volkswagen lists signal voltage below a threshold range of 2.74–3.26 volts. The chart does not identify which precise threshold applies to a particular calibration, so reducing the range to one universal number would add unsupported certainty.

The adjacent P240A and P240C entries classify the heater's open and high conditions. P240C uses current evidence, while P240B uses voltage. This difference matters when deciding what a test result actually demonstrates; one measurement type cannot simply replace the other.

Low voltage does not locate the defect

The quick reference does not supply a cause list or establish whether the heater, wiring or control stage is defective. It also does not equate a heater electrical fault with a measured tank leak.

Professional evaluation should identify the heater circuit on the correct engine configuration and use the complete workshop test. The source provides no resistance value, direct-power test or replacement recommendation. Preserve the low-circuit classification in the fault record so it is not confused with an unsuccessful EVAP leak test or an inactive pump motor.

Source: Volkswagen manufacturer diagnostic chart, physical PDF page 80; physical PDF page 87.