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Discussion Starter #1 (Edited)
I keep seeing the same question about this problem being asked again and again, so I am hoping that this short explanation will finally put things to bed.

If you have a van that has problems with the oil light flashing at low engine speeds or high engine speeds along with the buzzer or indeed flashing all the time then you may have a problem with the dynamic oil pressure warning system (DOP).

Why are there so many oil pressure warning problems on VW vehicles?

As usual VW has designed an overly-complex solution to a relatively simple problem - oil pressure monitoring. Because of the complexity of the DOP system, it has led to lots of problems with system itself rather than real oil pressure issues. Although it has to be said that such is the unreliability of DOP, that real oil pressure problems are sometimes ignored based upon the assumption that it is a 'wiring fault' or indeed vice-versa. It should be noted that VW abandoned DOP on later vehicles after about 2000/2001 and also on later (1999 onwards) 2.5TDI T4's. So, if you have a problem with oil pressure on one of these it is likely to be oil pressure sensor, wiring or an actual mechanical problem.

So what is DOP?

VAG vehicles have been using the DOP (dynamic oil pressure warning) system since the 1980's, this means that two oil pressure switches and engine RPM are used to determine oil pressure rather than the system of a single switch.

The VW rationale behind the DOP system is that low oil pressure problems are typical of high-mileage VAG engines with worn bearings and oil that is hot (and thin). The combination of thin oil and worn main bearings means that the oil pressure is marginal at lower RPM where the oil pump is not spinning as fast at idle speeds as it does when driving.



In order to address this perceived problem, the system basically monitors the low pressure sensor when the engine is below 2000 rpm and the high pressure sensor above 2000 RPM. This is done via the instrument panel which uses the 'w' terminal on the alternator to measure engine RPM and two switches - one on the head - It is normally closed and opens at (I think) ~0.3 bar ...





and one on the oil filter housing - this is normally open and closes at a fairly high pressure depending on engine type (1.4 bar for normally aspirated diesels and some TDs, and 1.9 bar for MK3 tdi (again - I think))...



Diagnosing faults with the DOP system

The instrument cluster only monitors the oil filter housing sensor when the engine is over 1800 - 2000RPM and if this sensor is not switched by 1800-2000 RPM the oil buzzer will sound and the oil pressure light will also flash. The body of the sensor is typically white, grey, or black in colour and is connected to the wiring harness with a yellow wire.

A. To test the high pressure sensor circuit and wiring (sensor for this is on the oil filter housing):

1. Disconnect the wire to the high pressure sensor on the filter housing and let it float (un-connected).
2. The oil buzzer should now come on and indicator will flash when the van engine speed is above 2000 RPM.
3. Now connect the yellow wire to ground and rev the engine past 2000 RPM… the buzzer should not sound at all.
4. If you fail either of these tests you have sensor issues, wiring, alternator wiring, or instrument cluster issues.

To test the sensor itself:
A test light between the sensor and the positive battery terminal should be 'off' at warm idle and come 'on' as you rev to 1800-2k RPM, if the sensor on the flange is working properly. If the buzzer still sounds with the wire to the sensor grounded the problem is most likely the wiring to the instrument cluster.

B. To test the low pressure sensor (sensor for this is on the cylinder head):

1. Disconnect the wire to the sensor and leave it float.
2. Connect a test light between +12V batt and the sensor.
2. Start the van and leave it idle - the light should go off - if it doesn't the you have a faulty sensor.
3. If it does and the oil light is still flashing then you have either a wiring fault or the engine speed signal from the alternator is missing.

So, the long and short is:

  • A flashing oil light, on its own at engine speeds of <2k RPM is a function of the low pressure sensor on the cyl. head. If the indicator stops flashing at engine speeds over 2k RPM then you should look at the low pressure sensor and associated wiring


  • A flashing oil light and buzzer are both a function of the high-pressure sensor on the filter housing. If this is happening you should look at the high pressure sensor and associated wiring


  • The high pressure sensor on the oil filter flange is only monitored when the engine is running at or over 1800-2000 RPM.


  • A flashing oil light at all engine speeds (and without buzzer above 2k RPM) is indicative of a missing engine speed signal (alternator 'w' terminal) - check to make sure that the instrument cluster is getting the correct engine speed signal from the w terminal of the alternator
I hope this has cleared-up any confusion regarding this common query.
 

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I'd like to add to this. If you fit the cluster from a 2.5 with rev counter into a 98 1.9 td when the engine gets hot ie after 10 Miles or so the oil light and buzzer may come on at tick over.
 

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Discussion Starter #4 (Edited)
I'd like to add to this. If you fit the cluster from a 2.5 with rev counter into a 98 1.9 td when the engine gets hot ie after 10 Miles or so the oil light and buzzer may come on at tick over.
Dennis,

As I said in the PM, you can't fit a 2.5TDI cluster to a 1.9/2.4D as there is nowhere to obtain an engine speed signal similar to that generated by the ECU in a 2.5TDI, so it will never work correctly and neither will the tach if fitted, obviously, regardless of any problems/fault with the DOP system
 

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I've been having some oil pressure system problems that don't seem to fit in with any of the common symptoms/causes listed here.

I have a 1.9td on ~175,000 miles.

Sometimes after I have driven the van fairly hard (ie faster than 50mph) when I come to slow down I start getting a red flashing oil light and beeps from my cluster. It usually clears itself after leaving the van switched off for a minute or so. Sometimes revving the engine hard clears it too. Sometimes after having driven it hard and getting the error it keeps coming and going until the end of the journey.

I've had a mechanic check my oil pressure under a variety of conditions and he has never managed to make it go low. He said if anything it is at the higher end of normal.

I do have a couple of small oil leaks but nothing that oil is gushing out of.

Does anyone have any ideas about this?
 

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Discussion Starter #6
I've been having some oil pressure system problems that don't seem to fit in with any of the common symptoms/causes listed here.

I have a 1.9td on ~175,000 miles.

Sometimes after I have driven the van fairly hard (ie faster than 50mph) when I come to slow down I start getting a red flashing oil light and beeps from my cluster. It usually clears itself after leaving the van switched off for a minute or so. Sometimes revving the engine hard clears it too. Sometimes after having driven it hard and getting the error it keeps coming and going until the end of the journey.

I've had a mechanic check my oil pressure under a variety of conditions and he has never managed to make it go low. He said if anything it is at the higher end of normal.

I do have a couple of small oil leaks but nothing that oil is gushing out of.

Does anyone have any ideas about this?
Sensor or wiring issues then
 

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I thought that too.

It's bizarre that it only happens after driving faster than 50. If I drive at 50 all day it doesn't happen.
 

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Discussion Starter #8
I thought that too.

It's bizarre that it only happens after driving faster than 50. If I drive at 50 all day it doesn't happen.
Not really that bizarre - electronic and electrical components can also suffer from thermal failure just like anything else...
 

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Not really that bizarre - electronic and electrical components can also suffer from thermal failure just like anything else...
Hmm, good point, I'll have a look at my loom and run the tests with the unplugging the sensors.

Cheers for clarifying things for me.
 

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Just found this thread whilst searching for oil pressure warning problems. Is there any chance mods could make it a sticky? As I think it's just solved my problems and I'm sure others will benefit from it tooT:

Cheers
 

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Hi Penbryn

I have just followed your instructions to the word.. Spot on mate. My high pressure sensor is NBG. Thanks saved me alot of time. A:

So my temperature dial on the dash does not move, any ideas would be very grateful.
 

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Penbryn, thanks very much for the post. You saved my day.



The local garage couldn't start my van so they tried to hit the starter motor to free it. (It was just a sticky ignition key). When they did this they chopped the rpm wires that were resting on top. Plonkers!

They then put 'low oil pressure' on the MOT form. There are some real cowboys out there.
 

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Cheers Penbryn

Was driving today when out of the blue the oil light and buzzer activated, of course my first reaction was AAAAAARGH
but after pulling over and checking all the obvious things, my second reaction as to scratch my head in puzzlement :*
So waited a while and started up again.....................no lights flashing, no buzzer buzzing
drove away, with a cautious mind.
a little while later, buzzers n lights, this time I messed with the revs and hit a few lumps in the road and found it to cause intermittant warning
This suggested wiring or earth related fault
After reading this post, I am sure that is the case now
So i am pre empting by saying THANK YOU A:
 

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Hello all,

V useful post, thats mt weekend sorted out!

Alongside the buzzer and waning light, my tacho needle is wandering about all over the place, can vary by 1000 rpm in either direction form any given point.

Does this go hand in hand with the oil pressure problem?

Thanks,

Patrick.
 

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this is very helpful , but my van is a 1.9 td v reg early 2000 with only 90k on the clock and a full service history, yet i get the oil light and beep every now and then, how do i check the oil pressure, i bought a new oil pressure switch from vw but they never said there was 2 of them. so does this mean there is only 1 on my van and where will it be?
 

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Discussion Starter #17
this is very helpful , but my van is a 1.9 td v reg early 2000 with only 90k on the clock and a full service history, yet i get the oil light and beep every now and then, how do i check the oil pressure, i bought a new oil pressure switch from vw but they never said there was 2 of them. so does this mean there is only 1 on my van and where will it be?
You don't need to check the oil pressure if the warning is intermittent at the moment.
Please re-read the thread carefully and that will answer all of your questions e.g.

so does this mean there is only 1 on my van
and two switches - one on the head - It is normally closed and opens at (I think) ~0.3 bar ...




and one on the oil filter housing - this is normally open and closes at a fairly high pressure...

if there is only one, then only one location will be stuffed... usually the one on the oil filter which, if it does not use DOP will be a sensor rather than a switch.

If volkswagen say there are two, then they are probably checking by the chassis number which means that they are probably correct. But like I said if you re-read the thread and then check your van, you will be able to confirm all of this.
 

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Was driving home and all was fine. Parked up for 5 mins came back out started it up and got the buzzer and flashing oil light. The buzzer goes off. But my battery light stays on and my rev counter does not really move. Took it for a drive and its still the same. Left it go cold tried again but still the same. Van runs fine starts fine.:confused: So does you think this is pointing at the alternator wire? :*
 

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The post above is more or less the problem i've got, but my tacho needle jumps about all over the place!

Not got check the sensors as yet as crawling about in the snow is not my idea of fun, no garage either so need to wait for a dry day...

My main question would be how is the tacho needle 'powered'?

Anyone got any ideas?
 
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