2005 AMF 1.4TDI no boost, wiring problem?

[Liamobrien2011]

Hi, so recently my girlfriend's car has gone into limp mode.

I'm getting a reoccurring error code:

18000: Altitude signal/boost pressure sensor implausible Ratio P1592

This is taken from my snap on scanner at work.

I know it isn't vagcom, but it has always served me well.

Now first things first... I changed the map sensor, cheap and easy to replace. Routine thing to do, I didn't even bother looking at the live data to compare the readings from the map sensor.

Problem is, the map sensor didn't solve my problem. I then set about looking further into the error and realised I can't clear the code. It is coming back instantly. And looking at the live data, the boost pressure sensor isn't sending any info back to the ECU, the new or old sensor.

So next step, ive checked the earth's under the battery box, and underneath theain ecu behind the airbox, a couple were corroded. I replaced one and cleaned up the other.

Still no joy. So question is.. Are there any other earth's that I've missed?

Is the wiring harness a common failure on these? I.E does it rub somewhere and cause a wire to earth out or break?? (It looks visually fine)

Pulling my hair out over this, any help would be so useful.

[sepulchrave]

Yes wiring.

[Breezy_Pete]

Within the plenum area under the wipers, there are a couple of places where big bunches of wire go vertically downwards out into the engine bay. There are rectangular grommets that are supposed to seal around the wire bunch and between the grommet and metalwork, but my observation is that after rain, drips or trickles of water can be seen running down these bunches of wiring into the engine bay (lower blue arrow is intended to show this).

 

I think it mostly runs around the outside of the grommet (blue lines and upper blue arrows) rather than between grommet and wiring bunch, but I can't be sure.  In theory, this shouldn't matter because the wires are all insulated with waterproof plastic, but if that cracks at any point in the lifetime of the loom/car, water will get in and corrode copper.  If any wires are joined within that area, the joins may be more vulnerable than the general wires. There may well be such joins in there, but I don't know.

 

 

 

I haven't any personal experience of this happening, but member jornyb very recently described finding some wires causing trouble in this sort of area, I think.  Link (see post #15).

Edited 11 October, 2016 by Wino

[Liamobrien2011]

@sepulchrave is the whole loom needed, or is the wire broken usually visible?

Thanks for your reply!

Regards Liam

[Liamobrien2011]

Within the plenum area under the wipers, there are a couple of places where big bunches of wire go vertically downwards out into the engine bay. There are rectangular grommets that are supposed to seal around the wire bunch and between the grommet and metalwork, but my observation is that after rain, drips or trickles of water can be seen running down these bunches of wiring into the engine bay (lower blue arrow is intended to show this).

I think it mostly runs around the outside of the grommet (blue lines and upper blue arrows) rather than between grommet and wiring bunch, but I can't be sure. In theory, this shouldn't matter because the wires are all insulated with waterproof plastic, but if that cracks at any point in the lifetime of the loom/car, water will get in and corrode copper. If any wires are joined within that area, the joins may be more vulnerable than the general wires. There may well be such joins in there, but I don't know.

I haven't any personal experience of this happening, but member jornyb very recently described finding some wires causing trouble in this sort of area, I think. Link (see post #15).

Thanks for your reply. I'll have the scuttle off that covers the wipers. And inspect the wiring!

Regards Liam

[Breezy_Pete]

I think that's unnecessary.

I'd expect the problem would more likely be below that grommet, in the engine bay, where the water has run down over the loom bunch.

[Liamobrien2011]

I think that's unnecessary.

I'd expect the problem would more likely be below that grommet, in the engine bay, where the water has run down over the loom bunch.

I'm still having problems with this.. I've stripped back wiring loom so that I can see what's going on. I've started from where the gromet is below the windscreen, to where the engine/gearbox mount is situated. The wires look all fine from there.

I think I'll test the resistance from each wire, (not that I know where all four wires go to) and see if there is a break.

Failing that, I'm tempted to just rewire the boost pressure sensor and meet the new wiring close to where it terminates (hopefully by the ECU?) see if that fixes the problem. Do you know what each wire does or know where I can find a wiring diagram?

Unless you have another suggestion!?

Regards Liam

[Breezy_Pete]

I should be able to look at a wiring diagram later, provided the hotel I'm heading for has heard of WiFi...

[Liamobrien2011]

I should be able to look at a wiring diagram later, provided the hotel I'm heading for has heard of WiFi...

Ahh fab! I have loads of photos, and may make it easier for you if I knew how to upload them/send them to you!

Liam

[Breezy_Pete]

MAP sensor wiring all seems to go to the engine ECU, direct.

Pin1, brown/blue, to ecu pin52

pin2, blue/yellow, to ecu pin 73

pin3, lilac/red, to ecu pin31

pin4, black/yellow, to ecu pin 71.

 

PMing you an email address now, if you want me to host/post any pics I can try.

[Liamobrien2011]

MAP sensor wiring all seems to go to the engine ECU, direct.

Pin1, brown/blue, to ecu pin52

pin2, blue/yellow, to ecu pin 73

pin3, lilac/red, to ecu pin31

pin4, black/yellow, to ecu pin 71.

PMing you an email address now, if you want me to host/post any pics I can try.

There isn't any chance this code could b related to the MAF, just wondering because of the way the error is worded with 'Altitude'

Any chance you have the wiring/pin numbers for that sensor too?

The was no resistance on any of those wires.

Looks like a possible ecu problem?

I'm going to double check the earths again

I'm also going to replace the map sensor itself again, with another genuine Bosch one, incase I picks a dosgy one up!

Thanks Liam

Edited 14 October, 2016 by Liamobrien2011

[Breezy_Pete]

Dunno about what causes that code. It's a bit confusing to me, cos this page refers to a G31 boost pressure sensor, and I don't see that amongst the engine-related wiring diagrams for an AMF, just the G71/72 intake pressure and temp sensor, the one you've replaced.

 

MAF wiring should be like this:

Pin1, not connected.

Pin2, black/yellow from fuse 7 (12v when ignition is on)

pin3, grey/white, to ecu pin49

pin4, red/green, to ecu pin30

pin5, grey/red, to ecu pin68

[Liamobrien2011]

Dunno about what causes that code. It's a bit confusing to me, cos this page refers to a G31 boost pressure sensor, and I don't see that amongst the engine-related wiring diagrams for an AMF, just the G71/72 intake pressure and temp sensor, the one you've replaced.

MAF wiring should be like this:

Pin1, not connected.

Pin2, black/yellow from fuse 7 (12v when ignition is on)

pin3, grey/white, to ecu pin49

pin4, red/green, to ecu pin30

pin5, grey/red, to ecu pin68

Hmm strange, you don't have a photo of the "G31" sensor do you? Just so I can relate back to the sensors I have visible!

I've finished work early so I'm soldering on, putting everything back together and collecting the other new boost pressure sensor from euros at 5pm.

I rechecked an earth I thought might have been bad, but I clearly cleaned it up and the copper is visible down the connector.

Going forward I'll check the maf wiring, fit the boost pressure sensor, check fuse 7, etc. Give it one final try. If all that fails I'll have to send the ecu away to ECU testing or somewhere simlar! :(

Thanks for all your help!! Liam

[Breezy_Pete]

Sorry no photo.

[sepulchrave]

You only have a MAP sensor which also has a built-in temperature sensor, no separate boost sensor.

[felicia16v]

Altitude sensor is usually part of the maf sensor, the loom rots down the back of the abs pump too.

in live data does the map sensor show a sensible reading with engine off?

I have tested the map sensors with a mityvac in the past, an old spark plug rubber boot is ideal to connect the map sensor to the mityvac and slowly pressurise it watching live data and the gauge on the mity.

I would test the maf wiring too.

[Liamobrien2011]

You only have a MAP sensor which also has a built-in temperature sensor, no separate boost sensor.

The car has both MAP and MAF sensors.

MAF is located off the the air box, on the pipe leading down to the low pressure side of the turbo.

MAP is located below the fuel filter on the upper side of the intercooler on the high pressure side of the turbo.

Thabks, Liam.

[Liamobrien2011]

Altitude sensor is usually part of the maf sensor, the loom rots down the back of the abs pump too.

in live data does the map sensor show a sensible reading with engine off?

I have tested the map sensors with a mityvac in the past, an old spark plug rubber boot is ideal to connect the map sensor to the mityvac and slowly pressurise it watching live data and the gauge on the mity.

I would test the maf wiring too.

I can get no "live data" from the new or old sensor.

The EML light is permanently illuminated and I can not remove it with the scan equipment available to me. The snap on scanner attempts to remove the code, but the ecu immediately has it back in its stored memory without starting the car, indicating a wiring, sensor or ECU fault.

I will check the MAF wiring later on this morning.

Thanks, Liam

[sepulchrave]

The car has both MAP and MAF sensors.

MAF is located off the the air box, on the pipe leading down to the low pressure side of the turbo.

MAP is located below the fuel filter on the upper side of the intercooler on the high pressure side of the turbo.

Thabks, Liam.

 

Your sig says you have a 1.4 16V, what car is this then?

[Breezy_Pete]

The clue is in the title...

[Liamobrien2011]

Your sig says you have a 1.4 16V, what car is this then?

My old car was Fabia 1.4 16v (witch I loved btw), this is my girlfriend's car witch is mentioned to begin with!

Sorry for the confusion.

[Liamobrien2011]

Just a random question, anyone know how much a new plastic insert for the fuel filter would cost?

The little plastic tags have one by one been broken off by myself and previous people :(

I'll try and get a photo up to illustrate.

Thanks Liam

[sepulchrave]

The clue is in the title...

 

Bum, my bad.

[Breezy_Pete]

Some photos of Liam's (click to enlarge):

 

 

 

 

 

 

Edited 16 October, 2016 by Wino

[Dazza95]

Just a random question, anyone know how much a new plastic insert for the fuel filter would cost?

The little plastic tags have one by one been broken off by myself and previous people :(

I'll try and get a photo up to illustrate.

Thanks Liam

Item 15 in the diagram:

http://workshop-manuals.com/skoda/fabia-mk1/power_unit/1.4/51;_55;_59_kw_tdi_pd_engine/fuel_supply_gas_operation/removing_and_installing_parts_of_the_fuel_supply_system/fuel_filter_summary_of_components/

One of the clips is broken on mine too :(