Engine Aftertreatment SCR System - Catalyst Temperature (Bank 1) High
The SCR system’s catalyst temperature is too high.
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What it means (plain English)
The computer is detecting that the temperature of the exhaust aftertreatment catalyst is exceeding safe limits, which can happen during excessive engine loads or faults in the cooling system.
What the computer is actually seeing
The Engine Control Unit (ECU) monitors the temperature via a sensor that reports back values; when the temperature exceeds 1000°F (538°C), a fault code is triggered to prevent damage to the catalyst.
What a healthy reading looks like
Normal catalyst temperatures range from 400°F to 800°F (204°C to 427°C) under typical conditions; anything above 1000°F (538°C) is considered excessive.
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. Inspect the exhaust temperature sensor wiring and connector for damage or corrosion. Decide: Is it intact? If yes, proceed to step 2. If no, repair/replace and retest.
- 22. Check the operation of the cooling system. Look for low coolant levels or faulty thermostat operation. Decide: Is the cooling system working properly? If yes, proceed to step 3. If no, repair cooling issues and retest.
- 33. Use a scan tool to monitor live data while operating the vehicle. Check actual exhaust temperature readings during normal operation. Decide: Are readings within expected values? If yes, proceed to step 4. If no, replace the exhaust temperature sensor and retest.
- 44. Inspect for exhaust system restrictions or leaks. Check for blockages in the DPF or SCR system. Decide: Are there any restrictions or leaks? If yes, repair those issues and retest. If no, further diagnosis may be required on the SCR system.
Common causes
- Faulty exhaust temperature sensor
- Exhaust leaks putting extra load on the system
- Cooling system malfunction leading to overheating of exhaust components
- Improper fuel quality or injection timing
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code present?
Driving with this code can lead to further damage to the exhaust system; it's advisable to fix the issue soon.
Will this code come back if I clear it?
It may return if the underlying issue isn't fixed, especially if overheating conditions persist.
Why is this code paired with high fuel consumption?
Excessive temperatures in the SCR system can lead to inefficient combustion or forced regeneration cycles, which consume more fuel.
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