P011A
Engine Coolant Temperature Sensor 1/2 Correlation
Engine cooling
Generic OBD-II
High
What it means
P011A sets when the two engine coolant temperature sensors disagree by more than the ECM permits. Most often one sensor (or its wiring) is reading wrong, though low coolant can create a genuine split between the two. The engine keeps running, but it's worth diagnosing so fuelling stays accurate and a real cooling problem isn't overlooked.
High
Can I keep driving? Usually driveable, but keep an eye on the temperature gauge — the fault can occasionally reflect low coolant or a real temperature problem.
Common symptoms
What you'll notice
- Check-engine light on
- Temperature gauge reading inaccurately
- Cooling fans running more or less than expected
- Rough or hesitant running when cold
Common causes
Most likely first
- One faulty engine coolant temperature sensor (sensor 1 or 2)Likely
- Wiring or connector fault at one of the sensorsCommon
- Low coolant level creating a genuine temperature differenceCommon
- Poor sensor ground or reference voltageLess often
- Faulty ECM/PCM (rare — rule out sensors and wiring first)Less often
How to diagnose & fix
Work through it in order
- Read freeze-frame data and check coolant level.
- After the engine has sat overnight, compare both ECT sensor values on a scan tool — both should read near ambient.
- Inspect the connectors and wiring at both sensors for corrosion or looseness.
- Measure the suspect sensor's resistance against a temperature chart and replace the one reading off.
- Repair any wiring faults. Clear and re-test.
FAQ
Quick answers
Is it safe to drive with P011A?+
Short trips are usually fine, but since it can reflect low coolant or a cooling issue, watch the temperature gauge and stop if it overheats.
Can I just clear P011A?+
It returns as soon as the two sensors disagree again — fix the off-reading sensor, wiring, or coolant level first.
Related codes
Often seen with P011A
Read & clear P011A yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX