P205C — Reductant Tank Temperature Sensor Circuit Low

OBD2 code P205C flags a problem with the sensor and actuator circuits (reductant tank temperature sensor circuit low). The car is usually drivable while you plan the repair. Common culprits: poor ground connection, open or shorted wiring in the circuit, control module driver fault.

powertrain (engine/transmission)

Is it safe to drive?

Short-term driving is OK In most cases the car remains drivable, possibly with reduced performance or a disabled auxiliary system. If symptoms include stalling, no-start or brake/steering warnings, treat it as urgent.

How to diagnose with an OBD scanner

  1. Read the code and freeze frame Connect an OBD2 scanner, confirm P205C is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
  2. Check for companion codes and TSBs Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many P0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
  3. Inspect wiring and connectors Visually inspect the wiring harness and connectors related to the reductant tank temperature sensor for damage, corrosion, chafing or poor contact.
  4. Subsystem check Check for supply voltage at the reductant tank temperature sensor connector first; then measure resistance from the signal wire to ground — near-zero ohms confirms a short to ground in the harness.
  5. Subsystem check Measure reference voltage, ground and signal continuity at the component connector.
  6. Subsystem check Wiggle-test the harness while watching the signal in live data — dropouts reveal broken wires.
  7. Verify the repair Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm P205C does not return.

Approximate repair cost

Repair cost depends on which component actually failed. Typical scenarios for P205C (parts and labor, USD, independent shop rates): Replace the faulty sensor or actuator: $150–$500; Repair wiring or connectors: $80–$250; Control module repair: $300–$1,000. Overall, fixing P205C usually costs between $80 and $1,000. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Common questions

What are the symptoms of P205C?

Drivers most often notice: the affected system operates intermittently or not at all, Check Engine Light on, increased fuel consumption in some cases, possible limp mode depending on the affected component.

How much does it cost to fix P205C?

Replace the faulty sensor or actuator — $150–$500; Repair wiring or connectors — $80–$250; Control module repair — $300–$1,000. Exact cost depends on the root cause, your vehicle and local labor rates — a proper diagnosis is the cheapest first step.

Will P205C clear itself?

Sometimes P205C clears after a few drive cycles if the fault was intermittent — for example a loose connector or a tank of bad fuel. The underlying cause usually remains, so the code tends to return. Clear it once; if it comes back, diagnose rather than erase it repeatedly.

What is the most common cause of P205C?

The most common causes are: poor ground connection, open or shorted wiring in the circuit, control module driver fault.

Is it safe to drive with P205C?

In most cases the car remains drivable, possibly with reduced performance or a disabled auxiliary system. If symptoms include stalling, no-start or brake/steering warnings, treat it as urgent.

What does P205C mean?

P205C (Reductant Tank Temperature Sensor Circuit Low) is stored when self-diagnostics detect abnormal readings or behaviour of the sensor and actuator circuits. It belongs to the powertrain (engine/transmission) category.

“Circuit low” means the voltage on the reductant tank temperature sensor circuit stays below the expected minimum — close to ground. The usual physical reasons are a short to ground, a chafed wire touching metal, a missing supply voltage, or a failed component dragging the signal down.

The module monitors this system continuously while driving. When readings fall outside the expected range for a defined number of drive cycles, it stores P205C and switches on the warning light. Freeze frame data saved with the code shows the exact conditions — rpm, load, temperature, speed — at the moment the fault was detected, which is the best starting point for diagnosis.

What causes P205C?

  • failed reductant tank temperature sensor pulling the signal low
  • signal wire shorted to ground (chafed insulation)
  • missing supply voltage to the reductant tank temperature sensor
  • faulty sensor or actuator of the affected circuit
  • control module driver fault
  • blown fuse feeding the circuit
  • poor ground connection
  • open or shorted wiring in the circuit

Common symptoms of P205C

  • the affected system operates intermittently or not at all
  • Check Engine Light on
  • increased fuel consumption in some cases
  • possible limp mode depending on the affected component

How to diagnose P205C

  1. Connect an OBD2 scanner, confirm P205C is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
  2. Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many P0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
  3. Visually inspect the wiring harness and connectors related to the reductant tank temperature sensor for damage, corrosion, chafing or poor contact.
  4. Check for supply voltage at the reductant tank temperature sensor connector first; then measure resistance from the signal wire to ground — near-zero ohms confirms a short to ground in the harness.
  5. Measure reference voltage, ground and signal continuity at the component connector.
  6. Wiggle-test the harness while watching the signal in live data — dropouts reveal broken wires.
  7. Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm P205C does not return.

How to fix P205C

Start with the cheapest and most common causes before replacing expensive parts:

  • Replace the faulty sensor or actuator — $150–$500
  • Repair wiring or connectors — $80–$250
  • Control module repair — $300–$1,000

How much does it cost to fix P205C?

Repair cost depends on which component actually failed. Typical scenarios for P205C (parts and labor, USD, independent shop rates):

  • Replace the faulty sensor or actuator: $150–$500
  • Repair wiring or connectors: $80–$250
  • Control module repair: $300–$1,000

Overall, fixing P205C usually costs between $80 and $1,000. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Can you drive with P205C?

In most cases the car remains drivable, possibly with reduced performance or a disabled auxiliary system. If symptoms include stalling, no-start or brake/steering warnings, treat it as urgent.

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