Ford Focus 1.6 Zetec SE MAP signal

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Ford Focus 1.6 Zetec SE MAP signal

Postby Avdr » Mon Jan 16, 2012 8:11 pm

Hi All,

Earlier today I went out to look at a 2003 Focus, as per title, that had suffered a period of total power loss on the motorway, no DTC's logged, and no seriously odd points to report - atleast not in as far as a visual inspection was concerned.

I was asked to concentrate my efforts on the electrical side, as the owner has a mechanic friend who would be looking at the car after me.

I have been completely unable to force the fault, or even have it present while I was there, the owner said it wouldn't even idle during the fault period.

I took a look at the MAP output, and have added the psdata file. My question is what is the actvity on channel A?
CHB appears to be an anologue output, and CHC is power at +5v. The sensor is a 4 wire unit, with the remaining wire being ground and not covered in the attached waveform.

The 'blip' is when I revved the car up. Wiring diagrams show the blue trace & red trace both as ECU inputs.

Can anybody describe the principal of operation of this sensor, and outline what the blue trace is doing?


Thanks

Andy
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FOCUS 1.6 ZETEC SE MAP SENSOR, ODD.psdata
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Re: Ford Focus 1.6 Zetec SE MAP signal

Postby Alan » Tue Jan 17, 2012 6:23 am

Hi,

Here is the waveform tidied up a bit (I usually like supply at the top, ground at the bottom and signal in the middle)

Ford Focus 1.6 SE Zetec MAP.gif


Channel A is odd as sensor outputs usually go from 0.5V to 4.5V. This jumps from 0V to about 3V and I can not decide if its a dodgy connection or this is a sensor with a digital output that is supposed to switch. OK just looked a bit more closely and it does seem to be switching - pulses repeat every 7ms or so, its not random.

If you still have the car can you capture the pulses again at about 20ms/div (or repeat what you have done with 10x more memory). The pulses are quite fast for such a long capture and you dont have enough memory to give a clear signal.

Not in the office so dont have access to data on the sensor so if anyone else knows whats going on please pitch in to help!
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Re: Ford Focus 1.6 Zetec SE MAP signal

Postby Avdr » Tue Jan 17, 2012 8:52 am

Hi Alan,

Apologies for the rather poor capture, I was aware of that myself, but by this point the customer was standing over me, and my aim was just to show him the reaction on CHB when I revved the car,

I no longer have access to the focus - and unless he comes back to me with further problems -I feel loathed to call him and ask to borrow it - as much as I am interested in R & D. At the time, with the car running perfectly, I reasoned there was little cause for concern regarding this signal, and my lack of understanding of its operation was the main issue.

I do have a peugeot 206 at the moment (in need of headgasket) that on visual inspection also has a 4 wire MAP sensor. Later on when I get it running I will have a look at that - but it could be that #4 wire is just a screen.

thanks for the input so far,

Andy
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Re: Ford Focus 1.6 Zetec SE MAP signal

Postby Avdr » Tue Jan 17, 2012 10:02 am

Quick Update, the suspected 4 wire sensor on the 206 turns out to be combined MAP and IAT, so no room for progression on that front.

Andy
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Re: Ford Focus 1.6 Zetec SE MAP signal

Postby Damian Mc Bride » Tue Jan 17, 2012 1:56 pm

Hi could the focus sensor be also be iat sensor just had bad conection
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Re: Ford Focus 1.6 Zetec SE MAP signal

Postby Avdr » Tue Jan 17, 2012 5:14 pm

Damian Mc Bride wrote:Hi could the focus sensor be also be iat sensor just had bad conection
Damian


That could well be the case, wiring diagrams don't show a separate IAT sensor, and I cannot remember seeing one. Perhaps CHB was picking up on the temperature, and CHA is as you say a poor connection on a digital MAP output.
Would make sense, I checked the IAT serially and was happy with the temp so gave it no further consideration.

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Re: Ford Focus 1.6 Zetec SE MAP signal

Postby Avdr » Tue Jan 17, 2012 6:07 pm

But then having said the above, it would seem unlikely that CHB could be the IAT signal. If it where, it would seem to show variation through almost its entire operating voltage - just to show a small change in temperature as a plug of air moves through the inlet tract - it would also suggest a PTC sensor which would be unusual.

EDIT : IGNORE THE PART ABOUT PTC, THAT IS INCORRECT. IT WOULD STILL BE AN NTC SENSOR.
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Re: Ford Focus 1.6 Zetec SE MAP signal

Postby Robski » Tue Jan 17, 2012 7:17 pm

What's the engine code on this ?

It will be a combined IAT/MAP sensor no doubt.

Where did you ground the black probes for each channel ?
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Re: Ford Focus 1.6 Zetec SE MAP signal

Postby Avdr » Wed Jan 18, 2012 7:49 am

Didn't get the engine code - it was just a plug in job that spilled over when I found no codes.

CHA was grounded on the top of the suspension strut. Laptop was sat on battery, preventing access to negative post.
The remaining channels had the ground wires unplugged.
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Re: Ford Focus 1.6 Zetec SE MAP signal

Postby Robski » Wed Jan 18, 2012 2:47 pm

Well for starters i would have grounded at Batt- & stacked the other channels at the same place.
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