I recently purchased a 98 Cherokee. The previous owner said the ecm was fried and he replaced it with a used one and after that the oil pressure gauge stopped working. I replaced the oil pressure sending unit to no avail. So in doing a little research I found that in 98 they came with either a oil pressure switch (one wire) that controlled the dummy light and a sending unit (two wire) that controlled the oil pressure gauge. If the ecm came from a Cherokee that had just the dummy light will it cause the gauge to not work? Previous owner never said if he had the ecm reflashed or not. Any help would be greatly appreciated.

 

Also forgot to mention I did perform a gauge test and all gauges worked flawlessly.