P2046 — Intermittent fault in DEF temperature sensor circuit

The engine control module is detecting an inconsistent signal from the diesel exhaust fluid (DEF) temperature sensor. This sensor monitors the temperature of the reductant fluid used to reduce emissions.

Common causes

The cause is almost always one of a few things. Here they are — P2046 rarely comes from anything outside this list:

• Loose or corroded sensor electrical connector
• Damaged or frayed wiring harness to sensor
• Faulty reductant temperature sensor
• Contaminated or degraded DEF fluid
• ECU software glitch or rare internal fault

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 electrical connector
2. Check wiring harness for damage or corrosion
3. Replace reductant temperature sensor if faulty
4. Flush and replace DEF fluid if contaminated
5. Update ECU software if recommended by manufacturer

That is what holds for P2046 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.