What Does P011A Mean?
The ECM has detected that the readings from ECT sensor 1 and ECT sensor 2 do not correlate within the expected tolerance range. Under normal conditions, both sensors should read within a few degrees of each other when installed in the same coolant circuit. A large discrepancy indicates one sensor is reading inaccurately or there is a localized cooling system issue causing a genuine temperature differential.
Common Causes
40%
One ECT sensor failing or drifting out of calibration, reporting incorrect temperature values
25%
Wiring issue on one ECT sensor circuit causing resistance offset (corroded connector, high-resistance splice)
20%
Air pocket or low coolant level near one sensor location causing one sensor to read air temperature instead of coolant
15%
Thermostat stuck partially open or closed creating abnormal temperature gradient between sensor locations
Diagnostic Steps
1
Compare ECT sensor 1 and ECT sensor 2 readings on a scan tool with the engine cold (sat overnight). Both should read within 5°F (3°C) of ambient temperature. Note which sensor deviates.
2
Verify coolant level is full and there are no air pockets in the cooling system. Bleed the system if necessary using the manufacturer-specified procedure and bleeder valves.
3
Disconnect each ECT sensor individually and measure resistance. Compare readings to the manufacturer's resistance-vs-temperature chart. A sensor reading more than 10% off specification should be replaced.
4
Inspect both ECT sensor connectors and wiring for corrosion, damage, or high-resistance connections. Measure voltage drop across each connector with the sensor active.
5
If both sensors test within spec electrically, monitor both readings during a full warm-up cycle. A thermostat issue will show one sensor reaching operating temperature significantly before the other.
Estimated Repair Cost
$75 - $350
Parts + labor, varies by vehicle and location
The ECM has detected that the readings from ECT sensor 1 and ECT sensor 2 do not correlate within the expected tolerance range. Under normal conditions, both sensors should read within a few degrees of each other when installed in the same coolant circuit. A large discrepancy indicates one sensor is...
The most common cause of P011A (Engine Coolant Temperature Sensor 1/2 Correlation) is: One ECT sensor failing or drifting out of calibration, reporting incorrect temperature values
Typical repair costs for P011A range from $75 to $350, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Inaccurate coolant temperature data can lead to improper fuel metering, degraded emissions, and unreliable cooling fan operation. If the ECM uses the incorrect sensor reading, the engine could overheat without warning.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P011A to identify the root cause.
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Quick Info
Category
Powertrain
System
Engine Cooling & Fuel Management System
Difficulty
Type
Generic (SAE)
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