OBD-II Code · Sensors
P0117
ECT Sensor Circuit Low Input
Severity
medium
Worth booking. It costs fuel, emissions or comfort until it is fixed.
Can you drive it
Only if running normally
A short trip to a shop may be reasonable if the light is steady and the car runs normally. Stop safely for a flashing light, severe shaking, overheating, loss of power, or another urgent warning. The code alone cannot confirm safety.
Indicative cost (USD)
$75–$200
Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
ECT reading too cold.
How a shop works this
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.
Note every code that is set, not just this one.
Codes that appear together usually narrow the cause faster than any one of them read alone.
Read the freeze frame — the conditions the fault was recorded under.
Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.
Confirm the fault is current rather than history.
Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.
Then work the likely-causes list in the order shown.
That order is what a shop checks first for this code — wiring and connections before the component they run to, because a connector costs nothing to inspect and is a common answer.
If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.
Common symptoms
- Check engine light
- Fan running constantly
- Poor cold-start fuel economy
Likely causes
- Failed sensorMost common
- Wiring short to ground
Read the full diagnostic procedureP0117 means the ECT signal voltage has dropped below the low threshold (typically under about 0.2 V), which the PCM interprets as an impossibly hot c…
P0117 means the ECT signal voltage has dropped below the low threshold (typically under about 0.2 V), which the PCM interprets as an impossibly hot coolant temperature.
Cheapest-first
- unplug the ECT connector with the key on.
- The signal wire should snap up to roughly 4.8 to 5.0 V (the PCM's pull-up reference).
- If it does, the sensor or its internal short to ground is the fault and a new sensor clears it.
- If the voltage stays near 0 V with the connector unplugged, the signal wire is shorted to ground between the sensor and the PCM. Backprobe the signal wire at the PCM connector to localize the short.
- At 70 F a healthy ECT should read about 2.5 to 3.0 V (2-3 kohm); a dead-short sensor reads near 0 V at all temperatures.
- Caveat: a coolant-soaked connector will mimic a shorted sensor because the coolant itself conducts; always dry and dielectric-grease the connector before condemning the sensor.
Vehicle-specific patterns1999-2006 GM 4.8/5.3/6.0 LS trucks get coolant intrusion into the ECT pigtail after a leaking intake manifold gasket, shorting the signal to ground.
- 1999-2006GM 4.8/5.3/6.0 LS trucks get coolant intrusion into the ECT pigtail after a leaking intake manifold gasket, shorting the signal to ground.
- 2003-2010Dodge Ram 5.7 Hemi has a TSB for chafed ECT signal wire against the intake bracket.
- 2002-2008Honda Accord/Civic K-series ECT sensors fail internally shorted after about 120k miles.
- 2004-2009VW/Audi 2.0T (BPY, CCTA) has the well-known green-top 4-wire ECT sensor that shorts internally; VW issued a redesigned black-top sensor as the fix.
Estimated repair$35 to $220.
Look up another code
P0117 — frequently asked
What does a P0117 code mean?
ECT reading too cold.
What causes a P0117 code?
Common causes: Failed sensor; Wiring short to ground.
What are the symptoms of a P0117 code?
Typical symptoms: Check engine light; Fan running constantly; Poor cold-start fuel economy.
Is it safe to drive with a P0117 code?
Only if running normally. A short trip to a shop may be reasonable if the light is steady and the car runs normally. Stop safely for a flashing light, severe shaking, overheating, loss of power, or another urgent warning. The code alone cannot confirm safety. Estimated repair: $75-$200.
How do I diagnose a P0117 code?
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed. 1. Note every code that is set, not just this one. 2. Read the freeze frame — the conditions the fault was recorded under. 3. Confirm the fault is current rather than history. 4. Then work the likely-causes list in the order shown.
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