Severity and Symptoms
Because the ECT sensor plays such a crucial role in engine operation, the P2186 code must be addressed urgently.
Symptoms of a P2186 code may include:
- Rough engine idle during cold starts
- Hesitation or stumbling during acceleration
- Rich exhaust smell, especially during cold starts
- Potential engine overheating
- Electric cooling fan running continuously or not at all
Causes
Possible causes of this engine code include:
- Low coolant level
- Faulty thermostat
- Defective ECT sensor #2
- Open or shorted wiring and/or connectors in the ECT sensor #2 circuit
Diagnostic and Repair Procedures
A good starting point is always to check the Technical Service Bulletins (TSBs) for your specific vehicle. Your issue might be a known problem with a published manufacturer fix, potentially saving time and money during diagnosis.
When diagnosing a P2186 code, I prefer to have appropriate diagnostic tools ready: a suitable scanner, digital volt/ohmmeter (DVOM), infrared thermometer, and reliable vehicle information source (such as All Data DIY).
I connect the scanner to the vehicle’s diagnostic port, retrieve stored trouble codes and freeze frame data, and document this information to begin diagnosis. Then clear the codes.
Next, I perform a visual inspection of the ECT sensor #2 wiring and connectors. Repair or replace any burnt or damaged wiring/connectors as needed and retest the system. If P2186 doesn’t immediately return, it might be intermittent. Operate the vehicle normally until the PCM enters OBD-II readiness mode or the code returns. If P2186 reappears, continue diagnosis.
Reconnect the scanner and access the relevant data stream. Filter the data stream to display only pertinent parameters for faster response. Monitor ECT sensor #2 temperature and voltage readings while checking for faults or inconsistencies. The PCM will interpret these as intermittent ECT sensor circuit signals. If inconsistencies exist, inspect the ECT sensor connector for corrosion. Check wiring routed near hot exhaust manifolds/collectors (potential intermittent ground short) and for loose or broken connector pins at the ECT sensor. Repair or replace faulty components as required.
Low engine coolant can also contribute to P2186 code storage. With the engine cold, remove the high-pressure cap and verify the engine contains the recommended coolant. If coolant level is more than a few quarts low, inspect for coolant leaks. A cooling system pressure tester can assist here. Repair any leaks, refill with proper coolant, and retest.
If the ECT sensor #2 reading (in scanner data stream) appears extremely low or high, suspect a faulty sensor. Using the DVOM, test ECT sensor resistance and compare results with manufacturer specifications. Replace the sensor if out of specification.
If the ECT sensor #2 reading appears slightly low or high, use the infrared thermometer to obtain actual ECT temperature. Compare the sensor signal reflected in the data stream with the actual ECT temperature and replace the sensor if readings don’t match.
Additional Diagnostic Notes:
- Ensure the engine has proper coolant level and functioning thermostat before attempting P2186 diagnosis
- Other ECT sensor codes and engine overheating codes may accompany this code type
- Diagnose and repair other ECT-related codes before addressing P2186