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90 420SEL, 95 E320 Coupe, 2000 SL500, 2009 ML320BT, 2016 Sprinter 3500, 90 420SEL
44 Posts
Discussion Starter #1
I found myself acquiring another W124 Coupe, my third to exact, that has an issue that I need help with. Its a California car with 80K miles, 1 year old engine wire harness. My oil pressure gauge always reads 3 bars while running and goes to O when turned off and .5 bar when the ignition is in position two. Plenty of oil circulating.
What is the procedure to test the sensor and the gauge. If the sensor is bad what is the best practice to replace the sensor?

Here is a pic.

Thank in advance for your help.

95" W124/ E220 MasterPiece and 01" W210/ E200 KOMPRESSER
257 Posts
Check your starter wire set first.
The smaller bio wires might all be gone.....left with your main power cord to the starter.
Rest three thin wires of the set are used for sensors, namely oil pressure, starter signal, and oil level, respectively.
The 3-pin connector is right mounted on the engine firewall in front of the brake fluid reservoir.

As for your questions...
If you like to test the sensor, u can ...
1. unplug its connector and key in position II (don't start engine)
--> the gauge reads 3, the sensor wire ok.

2. start you engine while waiting the pressure goes up, then stop the engine,
2.1 unplug its connector and ground the sensor wire, if the gauge reads 0 --> the sensor fails.
2.2 unplug its connector and ground the sensor wire, if the gauge reads 3 --> the wire fails.

Check and replace the sensor while the engine is cold.
Space is limited esp. under the oil filter housing ......if u like to unplug the connector and test.

Both sensors connected to the wire set are might consider to change them all.
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