: Atmospheric pressure sensor


cov75
3rd December 2012, 07:53 PM
Hi, Does anyone know where the atmospheric pressure sensor is on a 2004 Megane 1.9dCi? Many thanks if you do.

madnoel10
3rd December 2012, 08:06 PM
Are you referring to the MAP sensor??

Sometimes referred to as the turbo pressure sensor.

cov75
4th December 2012, 06:40 AM
Are you referring to the MAP sensor??

Sometimes referred to as the turbo pressure sensor.

Hi, thanks for your reply. I've had the car on the Clip box and the MAP sensor signal is fine, I also unplugged the MAP sensor with the car running and it's signal then dropped out. It's the atmospheric pressure signal that is grounding to earth which is the problem, I just don't know where the sensor is located on the car.

madnoel10
4th December 2012, 11:32 AM
To be honest I have never heard of an atmospheric sensor - I wonder if it's the MAF sensor which measures air intake volume and temperature.

cov75
4th December 2012, 12:53 PM
To be honest I have never heard of an atmospheric sensor - I wonder if it's the MAF sensor which measures air intake volume and temperature.

I checked the MAF sensor signal as well, the values seemed correct and again I unplugged it with the engine running and it's signal then dropped out. The value of the atmospheric sensor was in millibars pressure rather than a flow value. It's sometimes called a barometric pressure sensor as well. I've known them to be fitted in the boot in other cars but on mine it's gets worse when the engine is warm which makes me think its under the bonnet somewhere.

cov75
4th December 2012, 12:55 PM
I checked the MAF sensor signal as well, the values seemed correct and again I unplugged it with the engine running and it's signal then dropped out. The value of the atmospheric sensor was in millibars pressure rather than a flow value. It's sometimes called a barometric pressure sensor as well. I've known them to be fitted in the boot in other cars but on mine it's gets worse when the engine is warm which makes me think its under the bonnet somewhere.

Oh, just to add the car came up with fault code DF003 if that helps anyone.

madnoel10
4th December 2012, 03:32 PM
I have done a google search for Renault fault code DF003 and found at least one link which states the atmospheric sesnor is built into the ECU.

For copyright reasons I am unable to post the link.

My search words where renault fault code DF003

cov75
4th December 2012, 06:02 PM
I've done a google search using the key words you have and still can't find anything concrete about it, must be overlooking something. Thank you for you help I'll keep looking.

coup
4th December 2012, 09:04 PM
1013.2 hpa . pressure at msl under stp conditions.
That pressure may be built into the ecu, but I would think its only the MAF sensor that can modify this.
The Map sensor can only givr a prssure readout ,it doesnt have calibration like an altimeter where you can adjust for localised known height pressure readings at a particular time.
I would think the MAF is the only barometric ,environmental pressure sensor in terms of air temp and volume of air at certain rpms over a period of time.
Its readout could modify the ecu;s standard pressure from say 850 hpa to 1020 hpa or millibars if you like given the amount of air thats flowing thru and what temp its at..

Most columns of air above us in the UK area are above sea level,europe too , unless youre in some areas of holland..
Then there is..
Anyway.. I would suggest the localised pressure sensor on moving from a cold 200 ft altitude to driving thru an alpine pass on a hot day is down to the MAF.
It might not be as accurate as a correctly calibrated altimeter updated for local conditions but because a large amount of air like maybe 1000 times what you would breathe per second is passing thru the engine it would provide a good rough update of local air pressure.(to a standard value in the ecu)

dselec
10th December 2012, 03:36 PM
Hello
any idea how a MAF SENSOR i have right in air intake pipi going to air filer ,having only 2 pins can measure both temp and pressure[my sensor show about 1900 ohm in room temp] .

dselec
10th December 2012, 03:46 PM
[QUOTE=cov75;895239]I checked the MAF sensor signal as well, the values seemed correct and again I unplugged it with the engine running and it's signal then dropped out. ........Hello my sensor show 1900 ohm at ground level room temp how do u get/know the value of your sensor.

cov75
10th December 2012, 07:12 PM
[QUOTE=cov75;895239]I checked the MAF sensor signal as well, the values seemed correct and again I unplugged it with the engine running and it's signal then dropped out. ........Hello my sensor show 1900 ohm at ground level room temp how do u get/know the value of your sensor.
Hi, I had the car plugged into my clip box and used the current status function, This showed how much air was going into the engine, I can't remember what units it was displayed in but it went to zero when it was unplugged. The MAF sensor does not tell the car what the atmospheric pressure is, only the volume of air going in, another sensor tells it the atmospheric pressure so the car knows how much boost to allow on top of it.

schteevo
10th December 2012, 07:23 PM
The Powertrain Control Module (PCM) uses the Manifold Absolute Pressure Sensor (MAP) to monitor engine load. (NOTE: Some vehicles have a Barometric Pressure (BARO) sensor that is integral to the Mass Air Flow (MAF) sensor and do not have a MAP sensor. Other vehicles have a MAF/BARO and a redundant MAP sensor where the MAP sensor functions as a backup input in case of MAF failure.) The PCM supplies a 5 Volt reference signal to the MAP sensor. Usually the PCM also supplies a ground circuit to the MAP sensor as well. As the manifold pressure changes with load, the MAP sensor input informs the PCM. At idle the voltage should be 1 to 1.5 Volts and approximately 4.5 Volts at Wide Open Throttle (WOT). The PCM looks for any change in manifold pressure to be preceded by a change in engine load in the form of changes in throttle angle, engine speed, or Exhaust Gas Recirculation (EGR) flow. If the PCM doesn't see any of these factors change while detecting a rapid change in MAP value, it will set a P0106.
Symptoms

Possible sumptoms of OBD code P0106
Engine runs rough Black smoke at tailpipe Engine will not idle Poor fuel economy Engine misses at speed
Causes

Possible causes of OBD code P0106
Bad MAP sensor Water/dirt intrusion affecting MAP sensor connector Intermittent open in the reference, ground, or signal wire for the MAP sensor Intermittent short in the reference, ground, or signal wire for the MAP sensor Ground problem due to corrosion causing intermittent signal problem A break in the flexible air intake duct between the MAF and the intake manifold Bad PCM (do not assume the PCM is bad until you've exhausted all other possibilities)
Possible Solutions

Using a scan tool, watch the MAP sensor value with the key on, engine off. Compare the BARO reading with the MAP reading. They should be roughly equal. The voltage for the MAP sensor should read approx. 4.5 volts. Now start the engine and look for a significant drop in the MAP sensor voltage indicating the MAP sensor is working. If the MAP reading doesn't change perform the following: With the Key on, engine off, disconnect the vacuum hose from the MAP sensor. Using a vacuum pump, pull 20 in. of vacuum on the MAP sensor. Does the voltage drop? It should. If it doesn't inspect the MAP sensor vacuum port and vacuum hose to manifold for a restriction of some kind. Repair or replace as necessary. If there are no restrictions, and the value doesn't change with vacuum, then perform the following: with the Key on and engine off and the MAP sensor unplugged, check for 5 Volts at the reference wire to the MAP sensor connector with a Digital Voltmeter. If there is none, check for reference voltage at the PCM connector. If the reference voltage is present at the PCM connector but not the MAP connector, check for open or short in the reference wire between MAP and PCM and retest. If reference voltage is present, then check for existing ground at the MAP sensor connector. If it isn't present then repair open/short in the ground circuit. If ground is present, then replace MAP sensor.