Engine start and shutdown
Hi, I received Jeep Grand Cherokee 2008 with mercedes Diesel engine om642 3.0 with fault code (P0523 Engine Oil Pressure Sensor/Switch High Input). customer told me that the engine oil pressure sensor was damaged and he didn’t found one to replace and to start the engine the technician put a resistor 4ohms between the ground and the 5v supply on the sensor connector. We order new Orginal oil pressure sensor ,we remove the resistor and we install the sensor,fault code cleared but engine start for 1 second the it shutdown,we replace the engine control module but problem still same. If we put the resistor again as before engine starts. Plz advise and help.
Hi Aly, If it starts and runs with the resistor in at this age, install a fitting and a manual oil pressure gauge and be done with it possibly. Have you tested to make sure you have good oil pressure? If oil pressure is poor, that is a mechanical/ bearing failure issue. The other option is: The oil pressure sensor you installed is not correct or defective?
Hi, The sensor was ordered by vin number,it’s correct, On the diagnostic tool ,live data ,the engine oil pressure gives 1000mbar when ignition is on that is the atmosphere pressure,when engine cranks pressure increase to 1350mbar ,is this sufficient?
1350 mbar is around 20 psi Chrysler/Mercedes 3.0 diesel should have a min of 25 to 30 psi. I don't have the specs pulled up. I would have to find them. Also are there any codes in any other modules?
Key on engine off shouldn't the oil pressure be 0mbar?
I understand your reading is 1000mbar but I think it should read 0mbar KOEO. Is there a switch, wiring, connection, or pcm issue?
I think its reading absolute pressure. So the actual pressure is around 5psi. Im not sure if thats cranking or running. Spec says 16psi hot idle and over 50 while revving.
1000mbar is 1 bar which is atmospheric pressure or zero psi gauge
He's reading 1000mbar at key ON engine OFF and 1350 while either cranking or idling. That means the sensor is reading absolute pressure and the relative pressure of the oil is 350mbar or around 5 psi. Correct me if I'm wrong.
Hi Milos, You are correct according to the conversion table I have. 350mbar is just a hair over 5 psi. 1350 mbar is just over 19.5 psi
Aly, I would verify oil pressure is above minimum specs. What is scan data showing when this occurs? If it only runs for literally 1 second and then dies I feel that you may have a theft issue and not a oil pressure sensor problem. Oil pressure normally takes about 5~10 seconds to rise above minimum specs so this should not shut the vehicle off in less than 3 seconds.
Definitely check the actual oil pressure. If it is okay, I personally check the oiling passages or cleaner of some type to break up the possible clogged passages. As well if there is a chance the oil needs to be changed do that after the cleaning. I am not familiar with the circuit design. 1, 2 , or 3 wire?
Hi Brandon, This sensor is 3 wires circuit(ground ,5v,signal) Thanks
Hi Aly, This is an oil pressure combination safety switch if it is a 3 wire. Verify the basic oil level and oil pressure is within specification using a manual test gauge first. If it is, then suspect the connector on the switch. If the pressure is too low, the switch is interrupting a relay or PCM safety signal like it is designed to do. That would mean you have a badly worn engine…
If it runs with the oil pressure sensor bypassed but start stalls with the sensor in than you have an oil pressure issue. Either it is to low or to high, you need specs for oil pressure and a manual gauge installed to determine which condition you have.
Hi, Ok I will wait tomorrow to find a way to verify manually the oil pressure value. Thank u all.
Service information states the oil pressure for this vehicle should be 1.1 bar (16 psi) @ idle or 3.6 bar (52 psi) @ 3200 rpm. Now when you stated you replaced the PCM. Was it with a NEW one from the dealer or USED? If the PCM was replaced with NEW did you or the mobile tech input the IQA's for the injectors. This will prevent the vehicle from starting and running!!!
Aly, How did you clone it? Are the IQA's in the PCM?
I read the old ecu (flash and mpc)by ktag then i write it on the used pcm.
Since you have a used pcm installed in the vehicle I feel even more confident that you are having a theft issue. The issue with Chrysler products is not all pcms are interchangeable. Some have theft and some do not. If you installed a theft equipped pcm into a non theft equipped vehicle then you have just activated theft in every module on the network. Sometimes this can be removed but most of…
But than shouldn't it also stall when he has the oil pressure switch bypassed with a resistor?
I forgot about that aspect of the post. What bothers me though is that the resistor is placed between the ground and 5v reference not 5v ref and sensor signal return. Side note on these vehicles I thought by now all of these diesel equipped jeeps would be totaled or junked out by now… I had two customers that owned them and repair information was virtually non existent back in 2010 time frame…
I missed they wired it between the 5 volt reference and ground. You'd think that wouldn't change anything as I'm sure the 5 volt feed has a current limiting resistor in the PCM on that circuit.
Hi kevin, Yes the resistor is between the 5volt supply and the ground, Is this means bypass the sensor or what?
Hi, I remove the resistor and I connect fuse tester from the +12 battery to the 5v supply on the oil pressure sensor connector then I hear a click sound from the inlet manifold control valve and car start .same thing happened if I connect to any 5v supply on the engine circuit. What this means?plz more advice and help
Hello Aly, I question if the replacement oil sender switch was correct for this application. Problem never happened until original switch got damaged? What is your cranking oil pressure when measured with a manual gauge? Cranking oil pressure has to be recognized by the PCM to allow engine start. The pressure switch has to be correct.
Hi , These pictures of the live data of the oil pressure sensor when ignition on and while cranking .
That equates to about 14.14 PSIG. What is the minimum required when cranking for it to activate the fuel pump circuit?
Hi, I am not able to upload the video of the live data,plz send me your WhatsApp number to send u the video and u can see that pressure increases more than 2000mb.
Hello Aly, I was doing some reading on this and the oil filter cap has an O-ring. There is a TSB 09-005-07 that addresses the possibility of the cap O-ring being rolled out of place and pinched. Someone may have just left it off and not know any better. Quick lube strikes again?