P2045 — High voltage reading from reductant temperature sensor circuit

The engine control module is detecting an unusually high voltage signal from the reductant (DEF) temperature sensor circuit. This sensor monitors the temperature of the diesel exhaust fluid to ensure proper operation of the emissions system.

Common causes

The cause is almost always one of a few things. Here they are — P2045 rarely comes from anything outside this list:

• Faulty reductant temperature sensor
• Damaged or corroded wiring/connectors in sensor circuit
• Poor electrical connection or short circuit
• DEF tank temperature sensor malfunction
• ECU fault (rare)

Where to start

In the order a sensible mechanic would work — the cheap checks first, the expensive replacements only after:

1. Inspect and clean sensor connectors and wiring
2. Check wiring for shorts or damage, repair as needed
3. Test sensor operation and replace if faulty
4. Clear codes and test drive to confirm fix
5. Replace reductant temperature sensor if problem persists

That is what holds for P2045 in general. From here it depends on your engine — tell me which car it is and what it does, and I will give you the steps for it: real procedures, torque figures and diagrams instead of general advice.