Thu, 18 Apr 2013

Apparently Jeep changed the Grand Cherokee oil pressure sensor in 2003.
It's the same 4.7 HO engine, but they cheaped out on the sensor. The previous sensor actually sensed the pressure, and the gauge displayed the true oil pressure. But in 2003 they changed to an on/off sensor. If the oil pressure is high enough the switch is on (or maybe off), and if the oil pressure is too low, the switch is off (or maybe on). The computer gets the on/off signal, and it controls the oil pressure gauge stepper motor so it looks like it is sweeping up and down. But really the oil pressure always read just over half, or zero.
I found this out when I ordered the wrong ($50) sensor and installed it. The connector wouldn't fit. You can see that the original sensor has three pins, because it actually sends the correct pressure, and the new sensor only has one pin, since it's just on/off. At least the correct sensor is only $6, and I was able to sell the wrong sensor on eBay for about 2/3 what I paid for it.

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