Reductant Temperature Sensor Circuit High
P2045 indicates the reductant temperature sensor circuit is reading a voltage signal that is higher than the expected range. This sensor monitors the temperature of the diesel exhaust fluid (DEF) in SCR-equipped vehicles, and a high circuit signal typically means a wiring or sensor malfunction rather than an actual temperature problem.
What You Might Notice
- Reduced fuel efficiency
- Excessive black or white smoke from exhaust
- Diminished engine performance or reduced power
- Check Engine Light illuminated
- Possible SCR system limp mode activation
Most Common Causes
- 1
Defective reductant temperature sensor
The sensor itself may be faulty and sending an out-of-range high voltage signal to the PCM. Sensor failure is the most common cause of this code.
- 2
Wiring or connector issues
Corroded, damaged, or loose connectors on the reductant temperature sensor circuit can cause incorrect voltage readings. Check for frayed wires or poor connections.
- 3
PCM or control module malfunction
Rarely, the powertrain control module itself may be reading the sensor signal incorrectly or have an internal fault causing the high circuit code.
- 4
Short to voltage in sensor wiring
A short circuit to positive voltage in the sensor wiring harness can cause the circuit to register abnormally high, triggering the code.
How to Diagnose It
- 1
Check Defective reductant temperature sensor — The sensor itself may be faulty and sending an out-of-range high voltage signal to the PCM. Sensor failure is the most common cause of this code.
- 2
Check Wiring or connector issues — Corroded, damaged, or loose connectors on the reductant temperature sensor circuit can cause incorrect voltage readings. Check for frayed wires or poor connections.
- 3
Check PCM or control module malfunction — Rarely, the powertrain control module itself may be reading the sensor signal incorrectly or have an internal fault causing the high circuit code.
- 4
Check Short to voltage in sensor wiring — A short circuit to positive voltage in the sensor wiring harness can cause the circuit to register abnormally high, triggering the code.
How to Fix It
- 1
Replace reductant temperature sensor
Remove the faulty sensor from the DEF tank or line and install a new OEM or quality replacement sensor. Verify the new sensor reads correctly and clear the code.
- 2
Inspect and repair wiring and connectors
Check the sensor wiring harness and connector for corrosion, damage, or loose pins. Repair or replace damaged sections and ensure all connectors are clean and properly seated.
- 3
Test and reprogram PCM if needed
Use a diagnostic scanner to test sensor voltage and PCM response. If the sensor reads correctly but the code persists, the PCM may need reprogramming or replacement.
- 4
Clear fault code and perform road test
After repairs, clear the diagnostic trouble code and operate the vehicle to verify the code does not return. Monitor exhaust for normal operation.
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