Intake air temperature

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N

N5Fav

Member
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93
Location
South Leicestershire
Hello to one and all.

I have a '99 model P38 2.5 HSE.

The problem (or one of the problems) I have at the moment is to do with the air intake temp. On live data it is reading -40'c. Being situated in the mild East Midlands i don't think I have ever experienced any where near that temperature.

I have already fitted a new genuine Pierburg Air Flow Meter (to correct another running issue) so am happy it is not that. I am assuming then that it is going to be a wiring issue.

The only wiring diagrams I can find show the AFM with a flat plug, whereas mine has a round plug.

So can anybody give me the wiring description/diagram so I know which wires to check,

Thanks in anticipation
 
mcapinha said:
Which diagnostics tool are you using?
One of the latest nanocom updates fixes that problem.
Click to expand...

I have a new Nanocom (2 weeks old) and my air temp never gets out of the minus figures? I thought it was because the pre egr models had the temp sensor and the later ones didn't?

mine is a 1999 2.5 DSE Auto
 
What software version are you running on the Nanocom ?
Latest one is 1.21 and IIRC, the problem with the MAF sensor reading an incorrect temperature was solved in 1.20.
 
mcapinha said:
What software version are you running on the Nanocom ?
Latest one is 1.21 and IIRC, the problem with the MAF sensor reading an incorrect temperature was solved in 1.20.
Click to expand...


I would have to check once home, but I would presume if it's only 2 weeks old then it would be up to date?
 
mcapinha said:
According to the BBS forum, the MAF sensor reading was fixed in 1.20. That firmware was released in the 8th of February.

Sources: http://nanocom.blackbox-solutions.com/index.php/forum/26-edc/920-air-temperature-value and http://nanocom.blackbox-solutions.c...e-updates/1270-new-bbs-v1-20-firmware-upgrade
Click to expand...

Inlet air temp on EGR diesels reads -38.88 even at BBS 1-21. As far as i know the MAF does not measure air temp only flow for EGR. Inlet air temp appears to be a preset to force EGR operation.
 
Last edited:
I own a pre-MAF DSE so I haven't tested this myself. But I'm sure you'll agree that, from the 1st thread I linked to, it would look like that was fixed in 1.20 ?

I'm sorry I lead JohnnyCrash in the wrong way :/
 
mcapinha said:
I own a pre-MAF DSE so I haven't tested this myself. But I'm sure you'll agree that, from the 1st thread I linked to, it would look like that was fixed in 1.20 ?

I'm sorry I lead JohnnyCrash in the wrong way :/
Click to expand...

That refers to MAF reading zero fix. Not IAT reading -38.88 which they all seem to do. There is no connection to IAT input on EGR ECU. :)
 
There is an inlet air temperature sensor in the MAF. The figure shown with Faultmate/Nanocom is for the IAT that was in the manifold pre EGR, on the EGR EDC it always reads -38.88 as the manifold sensor is not present.
 
Datatek said:
There is an inlet air temperature sensor in the MAF. The figure shown with Faultmate/Nanocom is for the IAT that was in the manifold pre EGR, on the EGR EDC it always reads -38.88 as the manifold sensor is not present.
Click to expand...

Where is the air temp sensor in the MAF connected to Keith? Only two ECU connections to MAF. Pins 38 and 34. Pin 34 is not listed on ECU pin out diagrams. Goes straight from 33 to 35. IAT sensor input is pin 36. Bit of a funny one to be honest. Can't find a continuance connection anywhere for G6-9.

http://www.nanocom-diagnostics.com/downloads/1392441584.pdf
 
wammers said:
Inlet air temp on EGR diesels reads -38.88 even at BBS 1-21. As far as i know the MAF does not measure air temp only flow for EGR. Inlet air temp appears to be a preset to force EGR operation.
Click to expand...

There are 5 wires to the MAF, power, ground, flow sensor and temperature sensor.

Function as per RAVE below.

[FONT=Arial, sans-serif]Mass Air Flow Sensor (X105)[/FONT]
[FONT=Arial, sans-serif]The Mass Air Flow Sensor (X105) is a hot film[/FONT]
[FONT=Arial, sans-serif]sensor which has a heated surface maintained by an[/FONT]
[FONT=Arial, sans-serif]electrical current at a constant temperature. With[/FONT]
[FONT=Arial, sans-serif]cool air flowing past the sensor, the volume of air[/FONT]
[FONT=Arial, sans-serif]drawn into the intake manifold is measured by the[/FONT]
[FONT=Arial, sans-serif]electrical current required to keep the temperature of[/FONT]
[FONT=Arial, sans-serif]the hot film sensor constant. This data is used to[/FONT]
[FONT=Arial, sans-serif]calculate the injected fuel volume and the rate of[/FONT]
[FONT=Arial, sans-serif]Exhaust Gas Recirculation (EGR).[/FONT]
[FONT=Arial, sans-serif]The intake air temperature is measured by a[/FONT]
[FONT=Arial, sans-serif]thermistor with a negative temperature co–efficient[/FONT]
[FONT=Arial, sans-serif]and measures the actual temperature of the turbo[/FONT]
[FONT=Arial, sans-serif]booster air entering the engine. The ECM (Z132)[/FONT]
[FONT=Arial, sans-serif]uses this information, in conjunction with the[/FONT]
[FONT=Arial, sans-serif]manifold absolute pressure sensor, to determine the[/FONT]
[FONT=Arial, sans-serif]volume of air being drawn into the engine.[/FONT]
 
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Sorry Keith does not work for me. MAF does not control fuelling. Only air quantity for EGR. The ECU does need to know the air temp at the MAF however as higher or lower temp air would effect the hot wire and give a wrong flow reading. You will have noted the one wire to ECU from MAF has no noted function because there is no pin 34 in the ECU pin out diagrams. G6-9 is fed from same power source as engine and fuel temp sensors. The IAT preset is to force EGR operation by fooling the ECU that all air entering the engine is dense and oxygen rich.
 
wammers said:
Sorry Keith does not work for me. MAF does not control fuelling. Only air quantity for EGR. The ECU does need to know the air temp at the MAF however as higher or lower temp air would effect the hot wire and give a wrong flow reading. You will have noted the one wire to ECU from MAF has no noted function because there is no pin 34 in the ECU pin out diagrams. G6-9 is fed from same power source as engine and fuel temp sensors. The IAT preset is to force EGR operation by fooling the ECU that all air entering the engine is dense and oxygen rich.
Click to expand...
Not going to waste breath on this. There is no pin 34 on pre EGR EDC, there is on EGR EDC. The 2 wires from the MAF to the EDC are temperature and MAF hot film sensor analogue reading. You can physically follow the wires to the EDC.
 
Sorry but according to every pin out i have seen pin 34 is not present on the EGR ECU. Pin 38 is listed as MAF sensor. Pin 34 is the MAF IAT input on the petrol ECU but the Diesel does not have a pin 34. IAT for diesel is pin 36, unless one of the Land rover engineers does know the difference between 34 and 36. IAT temp measured at MAF would be pretty useless for fuelling adjustment. Fuelling for diesels is not controlled by airflow as it is in petrol engines. Fine fuel adjustment is set according to fuel temp, engine temp and rpm requirements.
 
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