There may be a Hood Ajar message displayed on the Driver Information Center on some 2014-2020 Impala models with the hood completely closed. The Check Engine MIL may be illuminated and DTC P257D (Engine Hood Switch Performance) also may be set.
If these conditions are found, disconnect the Engine Coolant Temperature (ECT) sensor and inspect for coolant leaking internally wicking up circuits 410 and 2761. (Fig. 4)
Fig. 4
Trace the circuits back to the X3 connector at the Engine Control Module (ECM). Look for any coolant contamination or corrosion at pins 7, 8, 23, and 24. (Fig. 5)
Fig. 5
The contamination may cause a short across circuits 5350 and 470 at pins 7 and 23, which are the hood open switch signal and sensor low reference. (Fig. 6)
Fig. 6
If coolant corrosion or discoloration is found, replace circuits 410 and 2761 from the ECT sensor to ECM connector X3. Replace the coolant temperature sensor and replace or clean connector X3 at the ECM.
For additional information and part numbers, refer to #PIC6460.
– Thanks to David Antal
