Symptoms
Potential symptoms include:
- MIL (Malfunction Indicator Lamp) illumination
- Poor fuel economy
- Poor driving performance
- Engine may run rough or blow black smoke from the exhaust pipe
- May not idle
- May start then stall
Causes
Potential causes of P2184 code include:
- Faulty ECT sensor #2
- Short to ground on ECT #2 signal circuit
- Defective or damaged connectors
- Damaged wiring harness
- Loose terminals on ECT or PCM
- POSSIBLY an overheated engine
- Faulty PCM
Possible Solutions
Since this code is for an abnormally low signal to the PCM from ECT sensor #2, the PCM detected an excessively “hot” condition in the engine coolant. This could be due to a faulty ECT sensor or wiring, but it could, in theory, be caused by engine overheating. So, if your engine has overheated, diagnose that first. That said, here are the possible solutions:
Using a scan tool, with KOEO (Key On Engine Off), check the ECT sensor #2 reading on the screen. On a cold engine, the ECT reading should match the IAT (Intake Air Temperature) sensor reading. If not, replace the ECT sensor #2.
1. If the ECT reading shows an excessively hot reading, for example, over 260 deg. F, then unplug the ECT sensor. This should drop the ECT reading to the extreme cold reading (about -30 deg. F or lower). If it does, replace the sensor, as it is internally shorted. If it does not change the reading, check for a short to ground on the ECT signal circuit wiring. It could be that the two ECT wires are shorted to each other. Look for any chafing or melted wiring. Repair as needed.
If you find no wiring issues and the ECT reading does not drop to extreme cold when unplugged, check the voltage coming from the PCM at the signal wire pin on the PCM connector. If there is no voltage or it is low, the PCM may be faulty. NOTE: On some models, it is possible for the 5-volt reference signal to be temporarily shorted. This can occur if an engine sensor internally shorts the 5-volt reference. Since the 5-volt reference is a “shared” circuit on many models, this will make it abnormally low. Usually, though, this is accompanied by several other sensor codes. If you suspect this might be the case, unplug each sensor until the 5-Volt reference returns. The last sensor unplugged is the faulty one. Replace and recheck the signal wire from the PCM connector.
2. If the scan tool ECT reading appears normal at that time, the issue may be intermittent. Use a “wiggle” test to manipulate the wiring harness and connectors while watching the ECT reading on the scan tool. Repair any loose or corroded wiring or connectors. You can check freeze frame data if your scan tool has that function. It will display the ECT reading when the fault occurred. If it shows the reading at the extreme hot end, replace the ECT sensor and see if the code returns.