Hi Guys! I really need your help! Yesterday I have changed the oil and oil filter in my Panda which has a 1.2 v8 FIRE engine. I changed other bits on the car as well at the same time, like spark plugs, valve cover gasket, thermostat, v-belt.

However, after starting up the car the red oil light didn't go away. I stopped the car immediately because I was afraid that I will trash the engine without oil pressure. I have checked again, the oil level is correct, no oil leak, and nothing sounded bad. I have connected to the multiecuscan and it came up with the error of P0520 - Oil pressure switch - Invalid signal - Fatal error. I started to look around at the switch and I could see that someone has been there before me as there was electrical tape around the connector. I removed it, but there is no major issue with the cable and the connector. Today I bought a new oil pressure sensor and installed it, but the problem is still the same. I can delete the code with the multiecusan and it doesn't come back until the car is turned on again. The strange part is that as soon as I put the ignition the code comes right away, I don't even need to start the egnine.

The car sounds, normal no knocking noises, I went for a small drive and everything is the same as before, so I'm sure that I messed up something with the wiring when I have installed the other parts. Do you guys have some idea where should I look?

Hi

it SOUNDS electrical to me..

But there is a possibility your new filter is too restrictive.. so oil pressure is low: hence the light

Try plugging the bare OLD switch into the wiring.. see if you can wriggle the wiring loom until the fault code is no longer present

I've tried to clean the connector with a pin and make it tighter, but doesn't seem to do anything I also think it is some electrical issue because as soon as I turn the ignition without starting the car, the code pops back on in Multiecuscan. I just don't know where to look now.

Maybe change the oil and filter again?

What make is the oil filter that you have fitted?

https://www.hengst.com/en/online-katalog/product/4276100000-01/

I used this one.

hi Endreoze.

from the info you have given it may be that the wiring loom to the connector is at fault, is it the type with two wires going to the sender as they may be connecting together internally.

If the sender is in the oil system is before the oil filter then any issue with the oil filter would not have any effect on the light.

Tim

endreoze said:

I've tried to clean the connector with a pin and make it tighter, but doesn't seem to do anything I also think it is some electrical issue because as soon as I turn the ignition without starting the car, the code pops back on in Multiecuscan. I just don't know where to look now.

Maybe change the oil and filter again?

Click to expand...

Hi,
Do you have a test meter of any kind?
Does the oil pressure switch connector have one or two pins?
check the resistance between the pins or if only one pin, from pin to body.
Normally the switch (assuming it's a switch and not a pressure sensor) is closed with no pressure and open with pressure. This means a wiring fault would have to be a short to ground.
Check the wiring loom(s) near anythen you disturbed and make sure it has not been trapped or is rubbing on a meatl edge or corner.

Robert G8RPI.

The connector is one pin and looks like this: https://www.fiatforum.com/gallery/data/500/DSCF6438.JPG

I have a multimeter but I don’t know what measurement i should see. Should I check resistance? (ohm)

the sensor should only have one wire

Unplugged it should measure 5 volts between this and the engine block


be careful. Its connected directly to the engine computer. Shorting to any live wires will result in an expensive repair


The switch itself should read very little ohms between its connector and the engine bock with the engine off


it should read open circuit. Same test but engine running.

endreoze said:

The connector is one pin and looks like this: https://www.fiatforum.com/gallery/data/500/DSCF6438.JPG

I have a multimeter but I don’t know what measurement i should see. Should I check resistance? (ohm)

Click to expand...

Use Ohms (200 ohm range if not automatic.
With car off and sensor UNPLUGGED check resistance between ground and the pin on the sensor. It should be less than 10 ohms.

With sensor still unpugged start the engine. The resistance should go very high, meter showing the sameas thee leads not connected to anything typically OC or OL. Don't leave engine running, but if the resistance goes high you have oil pressure.
If the switch goes high resistance with engine running you have either a short in the wiring or a faulty ECU.

Let us know what you find and we can give next steps.

Robert G8RPI

g8rpi said:

Use Ohms (200 ohm range if not automatic.
With car off and sensor UNPLUGGED check resistance between ground and the pin on the sensor. It should be less than 10 ohms.

With sensor still unpugged start the engine. The resistance should go very high, meter showing the sameas thee leads not connected to anything typically OC or OL. Don't leave engine running, but if the resistance goes high you have oil pressure.
If the switch goes high resistance with engine running you have either a short in the wiring or a faulty ECU.

Let us know what you find and we can give next steps.

Robert G8RPI

Click to expand...

Thank you guys I really appreciate your help.

So the result is that I have oil pressure because with the engine off the reading is 00.1 ohm (I have an automatic multimeter) when the engine running it is showing OL, I confirmed this multiple times, even with the old sensor. I measured it with the pin inside the oil pressure sensor and the outside of the sensor where the wrench fits.

I believe it is a wiring issue, as near the connector there was electrical tape and it was covering a previous cutting on the cable, however, the wire itself looks okay. So someone was there before I guess for measuring purposes and I really suspect the problem is there. It looks difficult to reattach this small plug to the wire, but I guess I should check first if power is going through there. How should I do it?

If the wire is shorted to earth you will get a low resistance between the connector and earth (same as no oil pressure). ECU will not raise a code until the engine starts.

If the wire is broken, you will get high resistance before engine starts. This could raise a code before engine starts.

The best option is probably to trace the wire into the loom and look for chafing or other signs of damage.

koalar said:

the sensor should only have one wire

Unplugged it should measure 5 volts between this and the engine block


be careful. Its connected directly to the engine computer. Shorting to any live wires will result in an expensive repair


The switch itself should read very little ohms between its connector and the engine bock with the engine off


it should read open circuit. Same test but engine running.

Click to expand...

have you measure the voltage ? should be 5v from the connector to the engine block

endreoze said:

Thank you guys I really appreciate your help.

So the result is that I have oil pressure because with the engine off the reading is 00.1 ohm (I have an automatic multimeter) when the engine running it is showing OL, I confirmed this multiple times, even with the old sensor. I measured it with the pin inside the oil pressure sensor and the outside of the sensor where the wrench fits.

I believe it is a wiring issue, as near the connector there was electrical tape and it was covering a previous cutting on the cable, however, the wire itself looks okay. So someone was there before I guess for measuring purposes and I really suspect the problem is there. It looks difficult to reattach this small plug to the wire, but I guess I should check first if power is going through there. How should I do it?

Click to expand...

as suspected. always worth checking but two faulty switches was always unlikely.

Peel back the wiring loom tape. Joint in a new wire with a new connector for the sensor and re-wrap the exposed section of wiring loom. Self amalgamating tape is good stuff much better than ordinary PVC tape.

This is the bee's knees method where the joint has high mechanical strength. Cover the bare joint with heat shrink sleeve.
https://www.youtube.com/watch?v=N8F6KcfB9Go

This also works fine for low power wiring and is more than strong enough for sensor wires.
https://www.youtube.com/watch?v=lrIefG-bbj8

endreoze said:

Thank you guys I really appreciate your help.

So the result is that I have oil pressure because with the engine off the reading is 00.1 ohm (I have an automatic multimeter) when the engine running it is showing OL, I confirmed this multiple times, even with the old sensor. I measured it with the pin inside the oil pressure sensor and the outside of the sensor where the wrench fits.

I believe it is a wiring issue, as near the connector there was electrical tape and it was covering a previous cutting on the cable, however, the wire itself looks okay. So someone was there before I guess for measuring purposes and I really suspect the problem is there. It looks difficult to reattach this small plug to the wire, but I guess I should check first if power is going through there. How should I do it?

Click to expand...

As suggested by koalar check for voltage beween the pin on the connector on the loom and chassis (ground) with ignition on but engine off.

It should be anything from 5 to 14 V (probably 5V). If you get less than 5V there are two possibilites

1/ Connection between ECU and plug shorted to chassis
2/ Faulty ECU

Note it is unlikely to be an open circuit as that would indicate good oil pressure all the time. The ECU could detect this as a fualt if engine RPM is zero but it's unlikely.

Unplug the ECU and use your meter to check the resistance from the semsor loom connector and chassis. If it's less than 100 ohms you have a short in the loom to find.
If it is open circuit probably a faulty ECU, but plug it back in and double check in case you have cleared the short by un-plugging it before buying a new ECu.

Robert G8RPI.

Measure and check as much as you can First. Its better to diagnose than just swap parts

Move things as little as possible to get the testing done. For example if the insulation is damage and touching the bodywork. Ounce you move the wires it will become difficult to find.

gone are the days of a simple on/off switch and bulb


here we have

oil pressure switch --> engine computer --> body computer --> dash module --> warning lamp all with interconnecting wiring


we dont know where along the trail the fault is. Hopefully its a simple wire between the oil pressure switch and engine computer.

all we know so far is the oil pressure switch is okay

the next logical step is to prove is the integrity of the single wire connected to it.

So I have spent the whole day trying to find the issue. I traced the wire all the way, which was really hard but I managed it. The wire goes into a connector behind the fuse box, and at the other end of the connector continues as a green wire directly to the main bigger ECU plug. I checked the continuity with the multimeter and it is good all the way to the ECU plug. No visible damage to the cable all along. While I was there, cleaned and lubed all the grounding points.

However, the wire definitely doesn't have 5V. But possibly I’m using wrong grounding points for the measurement. I used one at the battery negative terminal which goes into the main wiring loom.

As soon as I turn on the ignition multiecuscan comes up with the code again, without starting the car.

no 5v with the connector disconnected and the ignition on

correct ?

battery negative is fine

Could this be an ECU connector block issue?

DaveMcT said:

Could this be an ECU connector block issue?

Click to expand...

Why would it fail at an oil change though..

Or is it up around the air filter..?