P2AD0

Code

Generic P — Powertrain

Reductant Temperature Sensor B Circuit Intermittent

Brand: Generic

Type: P — Powertrain

Views: UK: 24 EN: 29 RU: 28

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Page language: EN

Causes

Loose, corroded, or contaminated connector at reductant temperature sensor B
Broken, chafed, or intermittent wiring/harness between sensor B and the engine control module (ECM)
Water ingress or physical damage to the sensor or connector
Failed/aging reductant temperature sensor B (NTC thermistor or similar)
Poor ground or reference/pull-up voltage problem at ECM or splice
Intermittent ECM/input module fault or software anomaly

Symptoms

Malfunction Indicator Lamp (MIL) or warning lamp illuminated (DEF/SCR fault)
Possible reduced SCR/aftertreatment performance or inhibited regen events
Warning message for exhaust aftertreatment or reductant system on dash
Intermittent or sporadic fault memory entries; vehicle may run normally between events

What to check

Read freeze-frame and stored data with a capable scan tool; note other related DTCs (reductant level, dosing control, NOx sensors)
Check if the code is current or pending; attempt to reproduce by key cycling and warming/cooling the sensor area
Visually inspect sensor B, connector, and harness for corrosion, bent pins, damage, water intrusion, or loose terminals
Backprobe sensor connector and observe signal while key on/engine running; wiggle the harness and connector to try to reproduce the fault
Check for correct reference voltage/pull-up and ground at the sensor connector with respect to vehicle ground
Measure continuity and resistance of wiring between sensor connector and ECM connector (check connector pinouts)

Signal parameters

Sensor type: typically an NTC thermistor (resistance decreases as temperature rises)
Typical behavior: resistance falls with increasing temperature; measured voltage (if used with pull-up) will vary inversely with temperature
Typical nominal ranges (generic): resistance ≈ 1 kΩ–20 kΩ across operating temps; voltage (with vehicle pull-up) typically ≈ 0.5–4.5 V depending on temperature and circuit design
Expected steady, smooth change in resistance/voltage with temperature; intermittent jumps, open/high or short/low readings indicate a fault

Diagnostic algorithm

Use a scan tool to record freeze frame data, live reductant temp B readings, and related DTCs. Clear codes and attempt to reproduce before repairs.
Visually inspect sensor B, connector, and harness for corrosion, loose pins, mechanical damage, or evidence of fluid ingress. Repair any obvious damage.
With connector disconnected, measure sensor resistance at known ambient temperature and compare to manufacturer specification or expected NTC behavior (resistance should change smoothly with temperature).
Backprobe the harness connector with the sensor connected: verify reference/pull-up voltage and ground presence with key on, then observe sensor voltage while monitoring temperature or warming the sensor (hot air) to confirm smooth change.
Perform a wiggle test on the harness and connector while monitoring live data to try to recreate the intermittent behavior. If the fault appears during wiggle, repair wiring/connector.
If wiring checks out, measure continuity and check for intermittent opens/shorts between sensor connector and ECM connector; repair any high resistance or intermittent connections.
If wiring and connector are good but readings are out of range or intermittent, replace the reductant temperature sensor B. Use OEM or equivalent-quality sensor and ensure proper sealing of connector.
After repair, clear codes and perform drive/soak cycle or reproduce conditions to verify the fault does not return. If codes persist and wiring is confirmed good, consider module input fault and consult OEM procedure for ECM/aftertreatment module diagnostics.

Likely causes

Loose or corroded connector at sensor B
Damaged/chafed wiring or intermittent short/open in harness to ECM
Failed reductant temperature sensor B

Fault status

⚠️ Status

Reductant Temperature Sensor B Circuit Intermittent — intermittent/open/short detected in sensor B circuit; ECM recorded unstable or invalid temperature input.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours