P2045 — Reductant Temperature Sensor Circuit High

P2045 — Reductant Temperature Sensor Circuit High. A fault in the sensor and actuator circuits. The car is usually drivable while you plan the repair. Typical causes: poor ground connection, blown fuse feeding the circuit, open or shorted wiring in the circuit.

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

Read the code and freeze frame Connect an OBD2 scanner, confirm P2045 is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
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.
Inspect wiring and connectors Visually inspect the wiring harness and connectors related to the reductant temperature sensor for damage, corrosion, chafing or poor contact.
Subsystem check With the reductant temperature sensor disconnected, measure signal voltage at the harness connector: a high reading with the component unplugged indicates a short to power in the harness; if it drops to normal, the component itself is faulty.
Subsystem check Measure reference voltage, ground and signal continuity at the component connector.
Subsystem check Wiggle-test the harness while watching the signal in live data — dropouts reveal broken wires.
Verify the repair Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm P2045 does not return.

Approximate repair cost

Repair cost depends on which component actually failed. Typical scenarios for P2045 (parts and labor, USD, independent shop rates): Control module repair: $300–$1,000; Repair wiring or connectors: $80–$250; Replace the faulty sensor or actuator: $150–$500. Overall, fixing P2045 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

Is it safe to drive with P2045?

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 OBD2 code P2045 mean?

What is the most common cause of P2045?

The most common causes are: poor ground connection, blown fuse feeding the circuit, open or shorted wiring in the circuit.

What are the symptoms of P2045?

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

How do I diagnose P2045 myself?

Start with a scan: confirm P2045, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the reductant temperature sensor, and verify the suspect component against live data before buying parts.

What does P2045 mean?

Behind P2045 is a specific failure in the sensor and actuator circuits: reductant temperature sensor circuit high. The onboard computer stores it in the powertrain (engine/transmission) group after verifying the fault over repeated checks.

“Circuit high” means the control module sees a voltage on the reductant temperature sensor circuit that is above the expected range — typically close to battery voltage. Physically this points to a short to a power feed, a broken ground return, or a failed component pulling the signal line high.

This code does not appear from a single bad reading: the module must see the fault condition repeat under defined operating conditions before it turns on the warning light. The freeze frame captured with P2045 — engine load, rpm, temperature, speed — tells you exactly when the problem occurs, so reproduce those conditions when testing.

Common symptoms of P2045

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

What causes P2045?

failed reductant temperature sensor pulling the signal high
open ground return of the reductant temperature sensor
signal wire shorted to battery positive
faulty sensor or actuator of the affected circuit
corroded, loose or damaged connector
blown fuse feeding the circuit
control module driver fault
open or shorted wiring in the circuit
poor ground connection

How to diagnose P2045

Connect an OBD2 scanner, confirm P2045 is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
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.
Visually inspect the wiring harness and connectors related to the reductant temperature sensor for damage, corrosion, chafing or poor contact.
With the reductant temperature sensor disconnected, measure signal voltage at the harness connector: a high reading with the component unplugged indicates a short to power in the harness; if it drops to normal, the component itself is faulty.
Measure reference voltage, ground and signal continuity at the component connector.
Wiggle-test the harness while watching the signal in live data — dropouts reveal broken wires.
Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm P2045 does not return.

How to fix P2045

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

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

How much does it cost to fix P2045?

Repair cost depends on which component actually failed. Typical scenarios for P2045 (parts and labor, USD, independent shop rates):

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

Overall, fixing P2045 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 P2045?