P24D2

Code

Generic P — Powertrain

Reductant Heater A Sense Circuit

Brand: Generic

Type: P — Powertrain

Views: UK: 18 EN: 33 RU: 24

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Page language: EN

Causes

Open or short in heater sense wiring (broken conductor, pinched or chafed wire)
Corroded or loose connector at the heater assembly or control module
Failed reductant heater element (open or changed resistance)
High resistance in the harness or poor ground connection
Faulty heater power/relay/fuse causing abnormal current flow
Failed heater sense sensor or temperature sensor integrated in heater assembly

Symptoms

MIL/Check Engine lamp illuminated
Possible dashboard message related to DEF/Reductant system
Reduced SCR/NOx system performance or regen inhibited
Heater may fail to heat DEF (cold conditions may present warnings)
Possible limp mode or reduced engine power in some vehicles

What to check

Scan for stored codes and freeze frame data; confirm P24D2 is current and note conditions when set
Visually inspect heater harness, connectors, and grommets for corrosion, damage, or moisture
Check fuses and relays for the reductant heater circuit
Backprobe the heater connector and measure supply voltage and sense signal while commanding the heater ON with a scan tool
Measure heater element resistance with connector disconnected and compare to expected range
Perform continuity checks from the control module pin to the heater connector pin and to ground

Signal parameters

Heater supply voltage: approx. battery voltage when commanded ON (typically ~11–14 V)
Sense circuit voltage: typically a low-voltage feedback/sensor signal (often 0–5 V) depending on design
Heater resistance (cold): commonly low ohms (example range ~1–50 Ω depending on vehicle/application) — compare to manufacturer spec
Current draw when heated: can be several amperes depending on heater rating (example ~0.5–10 A)
Expected behavior: sense signal changes (or resistance changes) when heater is powered; no open/short present

Diagnostic algorithm

Read and record codes and freeze frame; check for related DEF/SCR codes.
Perform a visual inspection of the DEF heater harness, connectors, and mounting for damage, corrosion or water intrusion.
Verify fuses and relays for the reductant heater circuit; replace if blown or faulty.
With the vehicle safe and hood open, backprobe the heater connector. Use a scan tool to command the heater ON and observe supply voltage at the power terminal (should be near battery voltage) and the heater sense/feedback signal.
With harness disconnected, measure heater element resistance. If open or out of expected range, replace the heater assembly.
Check continuity and resistance of the sense wire from the heater connector to the control module pin; repair any opens or high-resistance sections.
Inspect and clean connectors; repair or replace corroded terminals and reseal connectors to prevent moisture ingress.
If wiring and heater check good, test or substitute heater relay and inspect control module outputs. Replace control module only after exhausting wiring/part tests.
After repairs, clear codes and perform a functional test (command heater on/off with scan tool) and a driving/regeneration cycle to confirm the fault does not return.

Likely causes

Damaged connector or corrosion at the reductant heater plug
Broken wire or connector pin causing open circuit on sense line
Heater element has failed (open or out-of-spec resistance)
Blown fuse or failed relay supplying the heater
High-resistance ground or poor crimp in harness
Contaminated connector causing intermittent sense voltage

Fault status

⚠️ Status

DTC P24D2 — Reductant Heater A Sense Circuit: the control module detected an abnormal signal on the reductant heater A sense circuit (open, short to voltage/ground, high resistance, or unexpected feedback) while monitoring or commanding the heater.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-2.5 hours