P2ADD

Code

Generic P — Powertrain

Reductant Tank Temperature Sensor B Circuit Intermittent/Erratic

Brand: Generic

Type: P — Powertrain

Views: UK: 22 EN: 45 RU: 26

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Page language: EN

Causes

Damaged or chafed wiring in the reductant tank temperature sensor B circuit
Corroded, loose, or water-intruded connector at sensor or ECU
Failed or contaminated reductant tank temperature sensor (NTC/PTC thermistor)
Short to power or short to ground intermittently in harness
Poor or intermittent ground reference for sensor circuit
Intermittent ECU input/processing fault or internal ECU connector issue

Symptoms

Malfunction Indicator Lamp (MIL) or emissions/warning light illuminated
One or more SCR/reductant system warnings displayed (DEF/AdBlue fault)
Possible reduced SCR dosing or limp emissions strategy (depending on manufacturer)
Diagnostic trouble code P2ADD stored; freeze-frame may show intermittent values
Inconsistent or fluctuating reductant tank temperature readings in live data

What to check

Retrieve and record freeze frame and freeze-frame data; read any related codes
Visual inspection of sensor, connector, and harness for damage, corrosion, or fluid ingress
Check for service bulletins or manufacturer notes for this code (manufacturer-specific behavior)
Use a scan tool to monitor reductant tank temperature B live data while moving harness (wiggle test) to reproduce the intermittent behavior
Backprobe sensor connector and check signal voltage and ground with a multimeter or scope while changing temperature (warm/cool)
Measure sensor resistance vs temperature if sensor is a thermistor and compare to spec (if available)

Signal parameters

Typical sensor type: thermistor (NTC or PTC) — output reported as temperature via ECU
Signal wiring: 2 or 3 wires (signal, reference/pull-up, ground) depending on system design
Expected ECU input: low-voltage sensor signal converted to temperature (0–5 V nominal signaling range on many systems)
Normal operating temperature range for reductant tank sensor: typically down to -40°C and up to around +80–+125°C depending on vehicle (consult manufacturer spec)
Erratic condition: intermittent jumps, spikes, or frozen values in live data; sporadic open/short indications on continuity checks

Diagnostic algorithm

Read and record the P2ADD code and any related codes; note vehicle conditions and freeze-frame data.
Perform a visual check of sensor B, harness, and connectors for contamination, corrosion, loose pins, physical damage, or signs of DEF exposure.
With key on engine off (KOEO), backprobe the sensor connector. Check reference voltage (if present), signal voltage, and ground reference. Compare to expected ranges and note instability or intermittent loss.
Monitor live reductant tank temperature B while performing a wiggle test on the harness and connector to try to reproduce the intermittent behavior.
If the sensor is a thermistor, disconnect sensor and measure resistance at ambient temperature; if available, heat or cool the sensor and confirm resistance changes smoothly per spec. Replace if resistance is out of range or response is erratic.
Perform continuity and short-to-power/short-to-ground tests from sensor connector to ECU connector pins. Repair any open or shorted circuits, and repair damaged wiring or insulation.
Clean and reseal any corroded connectors or replace connector assemblies; ensure proper waterproofing for DEF applications.
If wiring and connectors check good and sensor bench tests normal, consider ECU input fault — perform ECU connector inspection and harness repairs. If ECU fault is suspected, follow manufacturer procedures for ECU testing/repair.
Clear codes and road-test to verify repair. Monitor live data for recurrence and re-scan for stored codes.

Likely causes

Corroded/dirty sensor connector allowing intermittent contact
Broken or fractured wiring at harness flex point near tank or mounting
Failed temperature sensor element due to contamination or exposure to DEF chemical attack
Intermittent short to ground or power caused by water intrusion or chafing

Fault status

⚠️ Status

P2ADD — Reductant Tank Temperature Sensor B Circuit Intermittent/Erratic. Intermittent or unstable temperature signal detected from reductant tank sensor B; inspect wiring, connector, sensor, and grounds.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours