Fault Family System: Powertrain (P-Codes) 5 SAE Codes

Reductant Tank Cap Switch

Diagnostic & Technical Explanation

Code P24CB (Reductant Tank Cap Switch Circuit) sets when the ECM sees an open, shorted, out-of-range, or intermittent signal from the switch in the diesel exhaust fluid tank filler cap that confirms the cap is properly closed to keep contaminants and moisture out of the reductant supply. Causes are a cracked cap seal that no longer closes the internal contact, DEF crystallization corroding the cap's contacts, or chafed wiring in the filler-neck harness.

These 5 diagnostic trouble codes share one detection mechanism and one repair path, which is why MechanicDB groups them into a single authored fault family rather than repeating the same explanation 5 times.

Codes in this family (5)

Code	Definition	Repair coverage
P24CB	Reductant Tank Cap Switch Circuit	3 ranked fixes
P24CC	Reductant Tank Cap Switch Circuit Range/Performance	3 ranked fixes
P24CD	Reductant Tank Cap Switch Circuit Low	3 ranked fixes
P24CE	Reductant Tank Cap Switch Circuit High	3 ranked fixes
P24CF	Reductant Tank Cap Switch Circuit Intermittent/Erratic	3 ranked fixes

What this page does not show

This page publishes the fault mechanism and the code index. The licensed dataset adds, for every one of the 15,886 codes, the full authored repair set (56,729 procedures in total) with the fields deliberately withheld here:

Procedures 2..n after the first-listed procedure
Aftermarket parts cost ranges in USD (est_parts_cost_min/max_usd)
Professional labor-hour estimates (est_labor_hours)
Step-by-step diagnostic and repair instructions
Replacement-part mappings and catalog lookups
6,637 manufacturer-specific OEM codes across 32 makes ($149 tier)

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