Reductant Temperature Too High - Bank 1
The temperature of the diesel exhaust fluid is higher than expected.
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What it means (plain English)
The sensor that checks how hot the diesel exhaust fluid (DEF) gets is saying it's too hot, which can happen when the engine is too hot or if there's a problem in the system.
What the computer is actually seeing
The Engine Control Module (ECM) monitors the reductant (DEF) temperature, expecting it to be between 9°C to 30°C (48°F to 86°F) during normal operation. When the temperature goes above the threshold (often around 70°C or 158°F), this code is set.
What a healthy reading looks like
Expect DEF temperatures to stay below 70°C (158°F).
Guided diagnostic — the DiagCoach way
Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.
- 11. Check the DEF level and quality — Low or poor-quality DEF can cause this. Top-off if necessary and clear code.
- 22. Inspect the wiring and connectors to the reductant temperature sensor for damage or corrosion. Repair if found.
- 33. Measure the DEF temperature with a scan tool — If it's above 70°C (158°F), check for overheating issues in the engine or DEF system.
- 44. If the sensor reading is normal, replace the reductant temperature sensor and retest.
- 55. Clear the code and monitor for reoccurrence — If it returns, further investigate the DEF system for malfunctions.
Common causes
- Faulty reductant temperature sensor
- DEF heater malfunction
- Wiring issues or bad connectors in the DEF circuit
- Overheating engine conditions
- Non-compliant DEF causing miscoding
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's moderate severity; you can drive but should address it soon to avoid emissions issues.
What happens if I ignore this code?
Ignoring it can lead to reduced DEF efficiency and possible engine overheating.
Why does this code sometimes come with other codes?
It can pair with other DEF or exhaust codes if there's a common issue in the system.
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