Engine Exhaust Temperature Sensor 2
This code indicates an issue with the second engine exhaust temperature sensor.
Heads up: this code wasn't in our hand-written library yet, so DiagCoach AI built this page on the fly. Double-check critical specs against service info before condemning parts.
What it means (plain English)
The engine is trying to monitor the exhaust temperature through a specific sensor but is getting an incorrect reading, usually because the sensor is faulty or there's a wiring problem.
What the computer is actually seeing
The ECU monitors the signal voltage from the exhaust temperature sensor 2 (usually ranges from 0.5V to 4.5V) and compares it to expected values during operation. If it detects a value that is either too low or too high (usually outside 0.3V to 4.8V), it throws the SPN 799 code.
What a healthy reading looks like
Expected voltage readings on the exhaust temperature sensor should be between 0.5V (cold) and about 4.5V (hot) under normal operating conditions.
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 wiring and connectors to exhaust temperature sensor 2 for signs of damage or corrosion.
- 22. Check the exhaust temperature sensor 2 using a multimeter — confirm it shows expected voltage values (0.5V to 4.5V) during different engine temperatures.
- 33. If the sensor is out of spec, replace it and recheck the system. If it's good, check the signal wiring continuity to the ECM.
Common causes
- Faulty exhaust temperature sensor 2
- Wiring issues (broken, frayed, or corroded wires)
- Poor connections at the sensor or ECM
- Short circuit to ground or power in the sensor circuit
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It may still be drivable, but you could experience poor performance or increased emissions, so fix it soon.
Will this code come back after clearing it?
If the underlying issue isn't resolved (like a bad sensor or wiring), it will likely return.
Why does this code sometimes pair with others?
It can be related to other temperature sensor faults or issues in the exhaust system, which can affect multiple readings.
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