Hi just joined, had my focus 1.6 tdci for two months now.

i notest that the check engine light was not working when you start the car.

i thought the bulb might have gone, or been taken out as i brought the car from auction.

But when i checked the bulb hole was filled up with black silicon........

cleaned it out and check engine light was then on.

put it on a tester and code p0120 was shown,

changed the MAF sensor and still the same code.

Tested it today with a multimeter and with the ignition on i got (starting from the left)

 

White red = 10.86V     Green red =Live 11.85V   black blue= Ground 0.01V  white blue=4.48V

Engine on...

White red = 11.86V     Green red =Live 12.85V   black blue= Ground 0.03V  white blue=0.19V

On incresed revving...

White red = 12.86V     Green red =Live 13.85V   black blue= Ground 0.04V  white blue=0.20V

Has anyone no why the white red wire has such hi volts... and why the white blue is 4.48v and then gose down....

i think there might be a wireing problem?

or do you think it is a bad Maf sensor?

 

 

 

3 hours ago, MAG said:

Has anyone no why the white red wire has such hi volts... and why the white blue is 4.48v and then gose down.

Pin 5 (Wh-Rd) is the flow output, it seems. All the analogue signals I have seen going into the ECU are in the 0-5v range, so I am a bit surprised by the high voltage. I think I would disconnect the MAF, apply 12v between pin 3 (live) and pin 4 (ground), and measure the output voltage on pin 5. Just in case an ECU or wiring fault is driving 12v into it.

Pin 2 (Wh-Bu) is the temperature output, there should (from the diagram), be thermistor between it and ground, I would not expect its reading to drop as the engine starts. It should give a resistance reading on a DMM that varies with temperature.

It almost looks like the wires have been muddled up somehow, wrong MAF? or wrong loom connections to the connector?

It is criminal, blocking up warning lights like that. There is a thread on here where a garage disabled an ABS warning light because they could not fix the ABS problem!

The block on the left of the pic is the ECU, the Gn-Rd wire comes from the battery via the engine management relay.

Thanks for your reply,

I think someone has messed with the wires!

i will retest tonight and see what happens,

thanks mark.

7 hours ago, Tdci-Peter said:

There is a thread on here where a garage disabled an ABS warning light because they could not fix the ABS problem!

Do you have a link to that thread Peter?  I'd be interested to have a read!

4 hours ago, Albert27 said:

Do you have a link to that thread Peter? 

I've always had doubts about the integrity of some garages, but this was still quite a shock to me!

7 hours ago, Tdci-Peter said:

I've always had doubts about the integrity of some garages, but this was still quite a shock to me!

Read this over lunch today at work.  Quite unbelievable!  I wonder what the outcome of the investigation was, and crucially, which garage was it?!  

Note that in the new draft MOT manual (to come into force in May but not 100% finalised) it is a requirement to check that engine management light comes on and then goes off in it's correct way.  I would imagine that some people will get round this by wiring the engine management light up to one of the other lights that is behaving correctly. 

Sounds like they had my car too...

it took some cleaning out..

 

Found the Maf wires have been re joined ....

 

going out to test now...

1 hour ago, MAG said:

Found the Maf wires have been re joined .

Those wires do not look right! Connector Faceview below.

What sort of animal did you buy the car from? Though to be honest, the only animal capable of such devious incompetence is H.Sapiens .

Just got back in, re-tested wires off the maf and run live and ground to sensor working fine (1.75v going up steady when reving it)

so reconected live and ground and tested fine (1.75v going up steady when reving it)

tested the white/red wire going back to the ecu but not conected to the maf and it test 12.65v

so the it must be picking up a live from somewhere?

Where is the ECU on the focus MK2?

thanks mark

1 hour ago, MAG said:

Where is the ECU on the focus MK2?

To get to the ECU, remove the passenger side front wheel and the wheel arch liner. Just in front of the wheel is a plastic box with an access door held in by about 4 screws. It is in there. The box is actually part of the air intake system.

There will be a headless security bolt holding the connector on, so it is not that easy to get at! (unless it has been tampered with already, of course).

The MAF live (Gn-Rd) should come from R11 in the Engine fuse box, via F35, in the same box. The other 3 wires go to the ECU.

If you have any suitable resistors, connect a resistor in the range 2k to 10k between the white/red wire and ground, see if that pulls it down. It is just possible the ECU has a pull up resistor to 12v inside it on that line. If so, it will have a fairly high value (>10k I expect).

But since when the MAF is connected, that does not pull it down much, it does look like a short to +12 is on that line somewhere.

.

Just had time to have a look at this today, and the car has been running fine getting 61.5 mpg last week on 334 miles.

Cut the white and red wire and tested at both ends. wire coming from the MAF = 0v

and the wire coming from the ecu = 12.65 same as at the Maf

Found 2 other wires with same v in a bit of a desparate state cut them but still no joy, white/red still showing 12.65v

 

So i think the Ecu has a short.

So will be selling as dont think it is worth changing ecu, open to offers its a Focus MK2 1.6 tdci in black good tyres all round new brakes, alternator and battery done 119,000 miles.

Call or text mark on 07811 110674

On 2/24/2018 at 3:09 PM, MAG said:

Just had time to have a look at this today, and the car has been running fine getting 61.5 mpg last week on 334 miles.

Cut the white and red wire and tested at both ends. wire coming from the MAF = 0v

and the wire coming from the ecu = 12.65 same as at the Maf

Have you tried with a resistor (a direct short to ground shouldn't hurt it ,but a last resort) to ground this wire from the ECU? As Peter has said, it may have a pull-up resistor internally which will cause it to read battery voltage until you put a load on it (basically what the MAF will do).

On 2/24/2018 at 3:09 PM, MAG said:

the car has been running fine getting 61.5 mpg last week on 334 miles.

That is a really good MPG for freezing cold weather in Winter!

My MPG has plummeted lately, my car does not like the cold, and nor do I!

Even a friend of mine with a 2 year old diesel Suzuki says his MPG is well down in this weather.

If it can do that without a MAF, then it is a pretty good engine, apart from the MAF problem.

In UK, EML on is not an MoT failure (yet!), I think I would keep it until better weather, then do a bit more investigating down at the ECU end. To make sure no wires are crossed, or as Ted (Micro) & I suggested, a pull-up resistor is giving the +12 reading, and the fault is in the MAF after all.

On 1/29/2018 at 12:50 AM, Tdci-Peter said:

All the analogue signals I have seen going into the ECU are in the 0-5v range, so I am a bit surprised by the high voltage. I think I would disconnect the MAF, apply 12v between pin 3 (live) and pin 4 (ground), and measure the output voltage on pin 5. Just in case an ECU or wiring fault is driving 12v into it.

Hi, here when you said apply 12volts on pin3 is that mean connecting it to the battery's positive?

Its just that i have a fault code p0101 on my grand cmax 1.6 tdci 2011, and a the maf sensor is not getting 12volts supply at all, i only get 7 or 8 volts ignition key ON and when i start the engine running the reading on my multimeter tester says 120 mV

the maf is a 4 pin, pretty much the same only mine is pin2 is the IAT and pin5 is the maf signal

On 10/1/2020 at 10:17 AM, jUn said:

have a fault code p0101 on my grand cmax 1.6 tdci 2011, and a the maf sensor is not getting 12volts supply at all, i only get 7 or 8 volts ignition key ON and when i start the engine running the reading on my multimeter tester says 120 mV

I don't know whether you have found it, but the entire schematic for the Mk3 Focus is on this site, and the CMAX is almost identical.

Yes, pin 3 should be battery positive, it is drawn as a direct connection via fuse F32 and relay R14 to a main battery positive (12v nominal) bus.

As you say, pin 2 is temperature, pin 5 is MAF signal, and pin 4 is Gnd.

Part of schematic below, of MAF. (1.6TDCI, Mk3)

 

Thanks Peter!

so it should be safe just for test to connect it directly to fuse 32, isnt it? and then later on trace where is that 12v getting lost, any ideas where to look for? i did took the air box out to get on the harness underneath and all the wires seems intact no obvious damage. I did check the diagram you send me and it says egr solenoid is connected on this fuse 32 as well so is it possible thats where im missing the 12 volts or voltage drop for the maf sensor. I checked the fuse 32 and its getting 12.6 volts ignition ON and about 14 v when engine is running. No fault code on egr

6 hours ago, jUn said:

so it should be safe just for test to connect it directly to fuse 32, isnt it? and then later on trace where is that 12v getting lost,

I would double check which pin really is the 12v supply, if all the colour codes match up then I would take that as being sufficient. Then link a wire direct from F32 (could use a piggy-back connector perhaps), to the Green-White wire on pin 3, close to the MAF connector. If that did cure the problem, it would be fine to leave the additional wire in place permanently, as long as it ran along a sensible route, and was not going to get damaged in use. Broken wires inside the wiring harness are quite a common problem, and it can be very hard to locate the break.