AFTERTREATMENT SYSTEM INLET TEMPERATURE LOW
The inlet temperature of the aftertreatment system is below the expected range.
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What it means (plain English)
Your truck's computer checks the temperature of the exhaust before it reaches the emissions treatment system. If it's too low, it won't work right because the system needs heat to function properly.
What the computer is actually seeing
The engine control module expects the aftertreatment inlet temperature to be between 200°F and 300°F (93°C to 149°C) during typical operation. If it reads below this range, it triggers this fault code.
What a healthy reading looks like
Expected inlet temperature is 200°F to 300°F (93°C to 149°C).
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.
- 1Check the wiring and connectors for damage or corrosion, especially at the temperature sensor.
- 2Inspect the aftertreatment inlet temperature sensor. Measure resistance; it should read within manufacturer specs. If not, replace it.
- 3Check engine coolant temperature. It should be at least 180°F (82°C) during normal operation. If it's low, investigate cooling system issues.
- 4Verify exhaust flow to make sure there are no blockages. A blocked exhaust can cause abnormal temperature readings.
- 5Clear the code and perform a road test. If the code returns, further diagnose the ECM or consider software updates.
Common causes
- Faulty aftertreatment inlet temperature sensor
- Wiring issues between the sensor and ECM
- Low engine coolant temperature due to a stuck thermostat
- Coolant leaks affecting heat exchange
- Faulty ECM calibration or software issues
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's drivable, but you may experience increased emissions and reduced performance, so fix it soon.
Will this code come back after clearing?
Yes, if the underlying issue isn’t resolved, the code will likely return.
Why is this fault sometimes paired with other codes?
This indicates multiple issues may be affecting the aftertreatment system, often related to temperature or sensor faults.
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