P205E

Code

Generic P — Powertrain

Reductant Tank Temperature Sensor A Circuit Intermittent/Erratic

Brand: Generic

Type: P — Powertrain

Views: UK: 30 EN: 35 RU: 29

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Page language: EN

Causes

Open or intermittent wiring in the sensor A circuit
Short to voltage or short to ground in the harness
Corroded, loose or contaminated connector at the sensor or PCM
Faulty reductant tank temperature sensor (NTC thermistor or similar)
Poor ground or reference voltage issues at sensor or PCM
Water intrusion or chemical contamination of the sensor/connector

Symptoms

Malfunction Indicator Lamp (MIL) / Check Engine Light illuminated
Reduced or disabled SCR/reductant dosing or regeneration strategies
Possible emissions-related limp/heavy fault mode depending on vehicle
Diagnostic trouble code(s) stored (P205E and possibly related codes)
Intermittent MIL that may come and go with vibration or temperature change

What to check

Read and record freeze frame and any stored pending codes; note operating conditions
Perform a visual inspection of the reductant tank sensor, harness and connector for corrosion, damage, or fluid intrusion
Wiggle test wiring and connector while monitoring live data or scanning for code set/reappearance
Backprobe sensor connector and check reference voltage, signal voltage and ground with ignition on and engine off/run as appropriate
Measure sensor resistance at ambient and compare to expected behavior as temperature changes (warm/cool) if known
Check for continuity and shorts to ground or battery between sensor signal and PCM

Signal parameters

Sensor type: commonly NTC thermistor (resistance decreases as temperature increases)
Typical supply/reference: 5 V reference (varies by manufacturer); some systems use pull-up to 5 V or internal pull-down — consult vehicle data
Expected signal voltage range: approximately 0.5 V to 4.5 V over operating temperature range (varies by manufacturer)
Expected temperature range: roughly -40°C to +120°C (sensor and vehicle specific)
Resistance behavior: high resistance at low temperatures, lower resistance at high temperatures (consult OEM curve for exact values)

Diagnostic algorithm

Retrieve freeze-frame and full code history. Verify DTC is current or pending and note operating conditions when it set.
Visually inspect sensor, connector and harness for contamination, loose pins, corrosion, cracking or reductant exposure. Repair obvious damage.
With ignition ON (engine off unless specified), backprobe the sensor connector and measure: reference voltage (from PCM), signal voltage, and sensor ground. Compare to expected ranges.
Operate wiggle test on harness and connectors while monitoring live signal. If the signal changes or code returns, isolate to wiring or connector.
Measure sensor resistance with connector disconnected. Warm or cool the sensor (carefully) and confirm resistance changes smoothly. Replace sensor if resistance is open, shorted or does not change as temperature changes.
Check continuity between sensor ground and PCM ground; check for shorts between signal and battery positive or ground.
Repair or replace damaged connector, wiring or sensor as indicated. Clean and protect connectors from reductant exposure.
After repair, clear codes and perform functional test: monitor live temperature signal through temperature changes and verify DTC does not return. Road test if required.
If wiring and sensor test good and problem persists, inspect PCM connector and pins. Consider PCM bench test or replacement only after ruling out wiring and sensor faults.

Likely causes

Damaged or corroded connector at the reductant tank temperature sensor
Broken or chafed wire causing an intermittent open/short when the vehicle moves
Failed temperature sensor element (NTC thermistor) due to contamination or age
Poor ground or weak reference voltage from PCM
Faulty PCM (less common) or intermittent internal circuit problem

Fault status

⚠️ Status

Reductant Tank Temperature Sensor A Circuit Intermittent/Erratic — PCM has detected an unstable or out-of-range signal from the sensor A circuit. Causes typically include wiring/connectors, sensor failure, or intermittent circuit faults.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours