What was the purpose of the maf sensor wiring mod?

[JTaylor2005]

Hi guys,

I have head about the MAF sensor wiring mod on these cars numerous times around the forums etc. I am wondering what the point was in doing it? I don't plan on doing it I just don't understand what it was to solve.

Looking at the wiring diagram doing the mod would seem to cause more problems. The "ground point" that people are cutting the cables off that the maf shares with the TPS sensor is actually going through a variable resistor inside the fuel temperature sensor first. This changes the reference point of the MAF sensor and TPS sensor most likely to stop heavy fuelling when the fuel temperature is hot.

Cutting the cables and earthing them directly to the ground on the car could actually cause issues with the running of the car if the fuel ever gets too hot.

[highwayman306]

What mod? I aint heard of this, you got any links?

[JTaylor2005]

This one http://www.theywhoshallnotbenamed/forum/...wiring-mod

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http://www.206info.co.uk/Forums/viewtopic/p=613852.html

[highwayman306]

Yeah, i wouldn't do that unless its throwing up a fault in the first place. My maf plug already looks like the "mod has been done" to it, going by the pic on .net. But i thought that was how the plugs as standard...someone might know more about this mate, but i honestly don't think and can't see why you would want to do that

[JTaylor2005]

I don't want to do it tbf. Just a warning not to do it. The mod isn't the cut green cable it is the red and white ones are cut further down the loom and then earthed to the chassis or whatever

[HDi--Power]

It just gives a better earth as the factory earth is shared by multiple sensors

[JTaylor2005]

The factory earth goes through a variable resistor that changes resistance depending on the fuel temperature sensor according to the wiring diagrams. Most likely to change fuelling depending on the temperature of the fuel.

[cully]

you need to look at the correct wiring diagram

the mod gives a clean earth to pins 3 and 6 of the MAF sensor
Pin 3 is ground ref for the IAT sensor
Pin 6 is ground ref for the MAF sensor

these earths before the mod are shared with the twin signals from the TPS sensor

the early HDI looms suffered from poor connections within the loom (common crimp point joints)

the side effect of this was the ecu would log a inconsistency fault on the TPS and the IAT sensors
the earth mod would fix it

the mod itself is a Peugeot FIX so it is a recomended fix from factory

[JTaylor2005]

Haynes manual must be wrong then because both pins 3,6, and then one of the tps all are shown to go through the fuel temp sensor resistor before going down to earth. Will see if I can get a pic

[cully]

it wont go through it, it will be a common ground linked to the other sensors ground pins which are grounded at the ecu not a seperate ground point

[darrenjlobb]

Cully is correct, this is a really common issue and causes some proper irritating engine lights / codes. Have resolved a few cars with this fix now!

[highwayman306]

the early HDI looms suffered from poor connections within the loom (common crimp point joints)
How early is this cully?

the side effect of this was the ecu would log a inconsistency fault on the TPS and the IAT sensors
the earth mod would fix it
What other noticeable side effects, other than codes and lights, would this show?

Cully is correct, this is a really common issue and causes some proper irritating engine lights / codes. Have resolved a few cars with this fix now!

I had never heard of it glad it was brought to light though

[JTaylor2005]

I will get u a picture of the way it's wired on the diagram.

[cully]

the early HDI looms suffered from poor connections within the loom (common crimp point joints)
How early is this cully?

the side effect of this was the ecu would log a inconsistency fault on the TPS and the IAT sensors
the earth mod would fix it
What other noticeable side effects, other than codes and lights, would this show?

ive never seen the issue on the latest 3 plug ecu's only single plug variants

it can also cause limp mod to be activated

[highwayman306]

it can also cause limp mod to be activated

Sound Cully, Ive been having issues with my maf and tps, would it be worth me doing this mod?

If so, its definitely wires 3 and 6 cut and earthed elsewhere

[cully]

I will get u a picture of the way it's wired on the diagram.

cut and link 3-6 to earth leave loom side free and insulated

i think you can earth the TPS circuits too for added security

[cully]

just to add to this

kayleys new car had the EML iluminated when we bought it
the car had already had this mod done to it well part of the mod but not very well

today i have sorted her EML light it is now off!
the Maf on her car is in a poor state so we are running the car Mafless ATM

to cure her EML
ive had to.....

link pin 4 on TPS to earth
link pins 6,3 on Maf to earth (i have not cut the loom side of these two wires)
Add chassis earth to ECU securing frame screw
clean up all earth leads on gearbox/chassis mounts under the battery
and for good measure i changed the fuel filter too EML was out before i did this

all the joints to the wires i have added are all soldered Not crimped

I did notice on this HDI Engine loom that there is no direct chassis earth like on the GTI6 Loom without going through the chassis plugs on the ns low inerwing

[Poodle]

Thanks for that, Cully. Were there any symptoms in how it drove besides the eml?

[cully]

Thanks for that, Cully. Were there any symptoms in how it drove besides the eml?

the ECU is a 362 one plug variant
planet listed the codes as
P0101 maf temp inconsistent Positive Break or short to earth
P0122 tps circuit 1 inconsistent Positive Break or short to earth
P0220 tps circuit 2 inconsistent Positive Break or short to earth

planet could reset the eml but it would return instantly
Running MAF unplugged on these ECU shows no EML

i did also meter out the signal lines from sensor plug to ECU Plug to prove they wernt broken,
i also metered the Earth paths while faulty the resistance to chassis earth was up to 5-6 ohms
once finished the same paths were down to 0.20hms

with the fault present the car drove like normal no oviouse side affects
once the modes were done and EML reset
the maf plugged in car would run with lack of power
unplugged the MAF power was back (typical test for a faulty MAF)

[pro_steve]

This is interesting, because I've never yet seen one which needed the earth fix, but obviously it is quite a common thing. I have had a few come to me with it already changed though.

From the looks of it you only need to do this if you get multiple open circuit faults, if you've just got MAF open circuit it's 99% just a bad MAF. If the TPS and the MAF are open circuit then look in to the earths.

[Poodle]

Brilliant, thanks mate.

[highwayman306]

Hmmm, might do this then cheers for the info lads, I'm sure i had those codes pop up before, def P0220 from what i can remember

[JTaylor2005]

Do you reckon this could cause idle fluctuation as well the tps sensor?

[cully]

bad earths could cause all types of faults on a ECU controlled engine,
as most of the sensors rely on a stable 5v reference to earth, if the earth is bad the signal from the sensors will fluctuate and the ecu will over compensate,
or if the sensor reading is outside its range/tolerance set buy map values,the ECU will flag a EML light if programed too.

that is why cleaning up the earth's on these engines is always a good starting point, before you start in depth diagnosis

[JTaylor2005]

Sweet will give it all a go then I have done ones that are under the air filter housing I think it was. Where else are there ones on these cars? I struggled to find them on mine tbf haha

[DeeTurbo]

There is an earth point under the ecu, to the right. I think it was for the water heater, can't remember what else uses that earth point.

[JTaylor2005]

So I found this thread again and realized I had not uploaded a pic of what I was on about. So here is it.

As you can see on the diagram the earth point for the maf, tps, and the ecu pin 22 all go to a single point. And then are earthed down through the mounting point of the fuel temperature sensor. Which then looks to go through a variable resistor in the temp sensor.

So surely cutting 3 and 6 and earthing them directly would bi-pass whatever that temp sensor and variable resistor are for?

[DeeTurbo]

The earth is through the ecu not the fuel temp sensor.

Sent from my Nexus 4 using Tapatalk

[Piggy]

No.
As everyone else said...shared earth.

[JTaylor2005]

Drawing looks a bit misleading then tbf