The OBD2 code P011A indicates a discrepancy or lack of correlation between two engine coolant temperature (ECT) sensors. This code suggests that the readings from the two sensors, which monitor the temperature of the engine’s coolant at different locations, do not align as expected.
Such discrepancies can lead to inefficient engine performance, improper heating, and in some cases, overheating. This issue is crucial as it directly impacts the vehicle’s cooling system, affecting overall engine health and efficiency.
P011A quick overview
| Meaning | P011A: Engine Coolant Temperature Sensor 1/2 Correlation |
| Is it serious? | Yes, because accurate coolant temperature readings are vital for engine management and to prevent overheating. |
| Possible causes | – Faulty ECT sensor(s) – Wiring or connector issues between the ECT sensors – Air pockets or flow problems in the cooling system – Faulty thermostat or water pump – Blockage or restriction in the heater core or EGR cooler |
| How to diagnose? | Inspect both ECT sensors for damage or corrosion and check their connections. Test the integrity and resistance of wiring between the ECT sensors. Verify coolant flow, looking for any blockages or air pockets that could affect sensor readings. Evaluate the thermostat and water pump for proper operation. Consider the cooling system components, such as the heater core or EGR cooler, for any restrictions. |
P011A Meaning
Imagine your car’s cooling system as the body’s way of sweating to cool down. The P011A code is like getting mixed signals about how hot it is, leading to confusion about whether to sweat more or less. This happens when two temperature sensors in the engine’s cooling system don’t agree on how warm the coolant is.
If left unchecked, it can cause your car to run inefficiently or even overheat. Fixing this can involve checking the sensors themselves, the wires connecting them, or even parts of the cooling system like the thermostat or heater core to ensure everything’s flowing smoothly and accurately.
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How to fix P011A – learn from mechanics
I looked into P011A service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.
Case #1: Mitsubishi P011A
Vehicle Information 2008 Mitsubishi Fuso FG140 FG84D 4.9L
Issue + Repair History
- Customer reported MIL lamp on
- Unable to retrieve temperature sensor reading, data stuck at 32°F
- No previous repair history related to this issue
Other OBD2 Codes + Test Results
- Error code: P011A
- Engine coolant temp reading stuck at 32°F
Mechanic Suggestions
- Check and clean threaded wire connection at the upper temperature sensor in the water outlet housing
- Consider using MUT-3 diagnostics for Mitsubishi vehicles if available
- Short the sensor to test wiring integrity and compare scan tool data with sensor open and closed
Final Fix
- Cleared the codes and cleaned the threaded wire connection at the upper temperature sensor in the water outlet housing. The vehicle has been driven for two weeks without recurrence of the issue.
Case #2: Mazda P011A
Vehicle Information 2014 Mazda CX-5 Grand Touring 2.5L
Issue + Repair History
- Vehicle arrived with code P011A, ECT correlation code
- Lack of heat at idle, with inlet hose to heater core hot and outlet hose barely warm
- Heater core flushed with no improvement
- No signs of coolant leaks or overheating
- Scanner shows ECTs reading correct coolant temp
Other OBD2 Codes + Test Results
- Error code: P011A
- Pressure tests conducted, no coolant leaks detected
Mechanic Suggestions
- Check for air pockets or flow problems, possibly due to a stuck open thermostat
- Verify coolant flow at the heater core, low flow could indicate a bad water pump or restricted heater core
- Consider replacing the heater core due to low flow or blockage
- Contact techline for guidance on heater core replacement if low flow/blockage is confirmed
Final Fix
- Customer went to Mazda dealer and confirmed diagnosis of a blocked or partially blocked heater core
- Replaced heater core, resolving the issue with heat not working at idle.
Case #3: BMW P011A
Vehicle Information 2015 BMW X5 xDrive35d 3.0L
Issue + Repair History
- Error code: P011A / 2C2200 (Coolant temperature sensor upstream of low-temperature EGR cooler, coolant temperature signals implausible with each other)
- Temp sensors replaced initially, but code persisted
- Water pump and thermostat replaced, code still present
- EGR coolers suspected to have issues, but replacement parts unavailable
- Removed EGR valve with cooler assembly and cleaned out built-up debris
- Final diagnosis: Coolant Changeover Valve was restricting coolant flow to the low side EGR cooler
Other OBD2 Codes + Test Results
- Error codes: P011A (Engine Coolant Temp Sensor 1), 2C2200 (Coolant temp sensor upstream implausible with each other)
Mechanic Suggestions
- Consider replacing the water pump and thermostat with Genuine BMW parts
- Replace both the water pump and thermostat, as they are common issues on these engines
- Address the coolant changeover valve as a potential cause of the restricted coolant flow
Final Fix
- Coolant Changeover Valve found to be faulty, restricting coolant flow to the low side EGR cooler
- Replaced the Coolant Changeover Valve, resolving the issue with the error code.
How to diagnose P011A
I made you an overview of solving this DTC, based on all the advice that was suggested by certified mechanics to address this issue in previously mentioned service cases.
| Diagnostic Step | Brief Explanation |
|---|---|
| Inspect ECT sensors and connections | Check both sensors for any physical damage or corrosion and ensure their connections are secure. |
| Test wiring integrity | Use a multimeter to test for continuity and resistance in the wires between the ECT sensors. |
| Verify coolant flow | Look for blockages or air pockets that could impact coolant flow and sensor readings. |
| Evaluate thermostat and water pump | Check these components for failure, as they play a crucial role in maintaining proper engine temperature. |
| Assess heater core and EGR cooler | Ensure there are no restrictions or blockages affecting coolant flow to these components. |
Car Diagnostics Training
- Car Electrical basics
- OBD-II scanner basics
- How to use an OBD reader
- Introduction to a Bi-directional Scan tool
- OBD scanner buyer’s guide + discounts
I test OBD-II scanners and make DIY Engine diagnostics guides to help you solve your car problems without having to depend on the mechanic. A lot of them will try to scam you or are just no help at all. About Juraj Lukacko