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Discussion Starter #1
Been having issues with my '04 Astra van the past few months (engine: z17dtl).

First occurred when was driving and the engine cut out and would not restart, just turning over. I went back to it the next day and it started fine so took to a garage who ran tests and replaced the cam sensor.

This didn't fix it and it continued to cut out so I plugged in a scanner and got the generic code: P0105
Manifold Absolute Pressure/Barometric Pressure Circuit Malfunction

So I took the MAP sensor out, gave it a clean and refitted, but the EML still coming on and also goes into limp mode after about a minute so won't rev above 3000rpm.

I had a quick inspection of the EGR valve and that looked pretty clean from one end so I don't think it's that.

Also changed the fuel filter. The turbo was replaced about half a year ago.

I have just today cleared the codes and fitted a "used" (supposedly working) MAP sensor to replace the original but no joy, same issues.

At a bit of a loss with what to do now, could anyone advise me whether it would be worth changing any of the following:

1/ MAF sensor
2/ Crank shaft sensor

Any advice much appreciated as this driving me mad! Cheers!
 

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I wouldn't throw any parts at it ,do you have the full code with symptom byte? and does your scanner record live data ?

It looks as though there are a few PO105 variants for your engine
P0105 2 Boost Pressure Sensor Circuit Low Input
P0105 1 Boost Pressure Sensor Circuit High Input
P0105 7 Boost Pressure Sensor Voltage Supply Circuit High Input
P0105 A Boost Pressure Sensor Circuit Range/Performance
 

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Discussion Starter #3
I wouldn't throw any parts at it ,do you have the full code with symptom byte? and does your scanner record live data ?

It looks as though there are a few PO105 variants for your engine
P0105 2 Boost Pressure Sensor Circuit Low Input
P0105 1 Boost Pressure Sensor Circuit High Input
P0105 7 Boost Pressure Sensor Voltage Supply Circuit High Input
P0105 A Boost Pressure Sensor Circuit Range/Performance
Thanks Valer, not sure don't think I can get full code info, but can get some live data - let me know if anything specific would help?

Just a thought related to the detailed codes you posted, is it possible it could be battery related? Only the battery in at the moment needs charging every few months so I'm wondering if the P0105 2 "circuit low input" could be the culprit if the battery's on it's way out?

Either way, will try a newer battery tomorrow and report back... thanks a lot!
 

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Discussion Starter #4
I've tried a new battery now but still no better and the P0105 code + EML keeps showing up + limp mode.

I ran a multimeter on the battery and it showed high voltage over 16V, which would point to the alternator regulator being shot.

That could tie in what you posted Valer: "boost pressure sensor voltage supply circuit high input"

I'll report back if this sorts the issue, cheers!
 

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Discussion Starter #5
Update:

I managed to drive to a scrappy (broke down number of times on an 8 mile drive, having to wait 20mins for restart each time) to find an alternator to see is this would solve the problem. The one we tried had corroded connector points and van didn't seem any better even though the points were cleaned before installation.. according to the scrappy it was barely used.

The mechanic also swapped the battery out for a newer one and said the voltage reading was lower (13.5v), although I don't understand why because I'd already tried swapping the battery and the reading was still high (16V+).

The relay metal casing is getting very hot to touch, and apparently the connector looks a bit fried. After swapping that for another relay, it didn't heat up but issues persist so that probably won't get to the root problem.

I'm getting desperate now and very close to getting the blurddy thing scrapperd!!

Its seems to be one of those issues that's very difficult to diagnose, but if anyone has experience with similar issues I'd much appreciate it!
 

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I'm taking it that the alternator issue has been solved now then? That's obviously an important one to get sorted as like you say the knackered reg on the old alternator is causing massive overcharging. It won't be the cause of this fault code unfortunately however - the boost pressure sensor, like all the other sensors on the car, run off a regulated 5v signal from the ECM, so regardless of fluctuating battery voltage during normal running, the upper limit for these sensors remains at a constant 5v to give consistent readings.

That doesn't mean to say that hugely overcharging alternators don't upset things electronically, but I would have thought you'd be seeing all sorts of voltage related codes.

In terms of live data, you need to look at the readings for boost/MAP sensor and barometric pressure (basically atmospheric pressure) with either the ignition on or even just the engine ticking over. They'll probably be listed in kPa, and if you're roughly at sea level they'll both be reading around 98kPa (pretty much 1bar atmospheric). That fault code is basically flagged because the comparison from the two readings doesn't match.
 

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Discussion Starter #7
Thanks for the input mate appreciate it, no the mechanic reckoned the original alternator might be fine as he seemed to think it was the old battery giving a high voltage reading which I didn't understand myself?

Ah that's good to know about the boost sensor voltage input etc thanks.

He's going to hook up a diagnostic to it tomorrow so I'll report back if anything useful comes back.
 

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The wiring to the glow plug relay module (casing overheating) also seems suspect so the mechanic is sorting the wiring and changing the relay module which hopefully will sort the engine cutting out issues.

I've been reading that when the glow plugs stay on all the time and therefore overheat it is most likely linked to the barometric pressure sensor, which brings me back to the original fault code.... could the cause of the relay overheating be related to the pressure sensor (ie. original P0105 code) or is the boost pressure sensor different beast to the barometric pressure sensor as I couldn't find information on this ?
 

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The boost sensor senses the pressure in the inlet ,the barometric sensor is in (and part) of the ecm ,
one of the four possible codes variants is thrown when the two values are out of spec with each .
There is also a field remedy for a modified boost sensor plug for the PO105 code
 

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Hi there , MAP sensors on Diesels seem to be different to Petrol's, on a Petrol it measures Vacuum, i think on a diesel it might measure pressure but not to certain on that, MAP stands for Manifold Absolute Pressure, which might be below or above atmospheric pressure....

So i would try this, there are probably 3 wires on the MAP sensor, one should be 5 volt, one is an earth and the last one is the sensor wire, so i am sure you can test the 5 volts and the earth? now the sensor wire goes from around 0 to 5 volts if its at Idle say about 0.5 volt, and when you snap the throttle it should go to around 4.5 volts...if it doesn't change and you have a vacuum/air supply to it then you need a new sensor....unless anyone else knows different.

The Crank sensor is a bit moe difficult to test, its probably magnetic and gives out an AC wave form....you can check its resistance, you could put an AC meter across it and check for about 1 to 2 volts output or best of all you could put a scope on it...best of luck from Fred in Essex.
 

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Discussion Starter #11
Thanks @Valer @g4vvq1983

The mechanic has now repaired the dodgy wires on the relay module and also replaced the module itself which was fried + put in a newer battery. He ran the van earlier but still cutting out... :mad:

The crank sensor is flaging up after hooking up a full diagnostic, so that's the next part to replace.

That "field remedy" connector replacement PDF you posted @Valer on the P0105 looks just the job thanks alot and will look at doing that when I get the van back hopefully next week.

So for now it's a case of ticking off the likely suspects and praying that the ECU hasn't gone south. :coffee:

Thanks again for all the input, it's given me a lot more to go on.
 

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Discussion Starter #12
Update:

Getting somewhere now, replacing the crank sensor has seemed to have solved the issue of van cutting out.

Now all that's left is the original P0105 code which still seems to be causing "limp mode", so having tried replacing the MAP sensor itself I'm now going to follow the PDF @Valer posted.

The PDF says to replace the MAP sensor connector as its a common fault in production... now to try and find a connector and replace it...
 
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