Air inlet air pressuse sensor circuit disable

senatorjohn · **Posted:** Tue Sep 23, 2014 9:46 pm

Hi.
Is it possible to disable the air inlet air pressure comparator circuit with any of the aftermarket tunes so it does not set the check engine light?
John

gmctd · **Posted:** Tue Sep 23, 2014 10:38 pm

If you're measuring ~3.78 v with IGN on, engine off, that is incorrect - at atmospheric pressure voltage should be more or less than right around 2.0v, depending on your altitude - voltage increases as Boost increases, with max Boost = ~4.7v - if 3.7v is a true indication of local Baro, I'd think you'd find it difficult to exhale....................

Anyhoo, it is a combo press\temperature sensor, used to calculate required fuel volume per air mass from below Death Valley to the peak of Mt McKinley - you'd miss it severely if disabled, IMO.

senatorjohn · **Posted:** Wed Sep 24, 2014 1:14 am

Hi gmctd.
Thanks for your reply. The sensor circuit I am having a fight is not the boost pressure / air temp., but the one used to measure air cleaner restriction. It does nothing else as far as I can work out. Open to all ideas and suggestions.
John

gmctd · **Posted:** Wed Sep 24, 2014 3:22 am

Ok, my bad - that's the MAF sensor, used for the EGR - most ECO tunes that eliminate the EGR also eliminate that sensor - was also a simple ckt generated here back in ought 7 or so, called the SEGR, which eliminated that sensor - a schematic was posted with parts list, also may be a few that came available as folks upgraded their ECM - possibility you could find one with a search thru the parts sections - or go big-time with an ECM upgrade, from mild to wild - a $20. MPPS setup from CHINA (on eBay) allows you to load and reload various tunes - checkout the posts under DIY ECU reflash and various others

viewtopic.php?f=98&t=78418

I had an epiphany while I was in the rain locker: you're troubleshooting the MAF sensor, DTC0100, when you should be troubleshooting the BOOST sensor DTC0105, back on the rear of the intake manifold,also called the inlet or intake air pressure sensor - give that a whirl, why don't you................

Also, a 'nuther KJ CRD member from down under is CRD JON - maybe you could also give him a buzz for some local camaraderie and commiseration - just search his member handle in search, members, and user control panel....................

senatorjohn · **Posted:** Wed Sep 24, 2014 6:08 am

The code I have is P0105, inlet pressure sensor signal plausibility, or sensor signal high or low. It is not the MAF sensor, it is upstream of the MAF sensor. There are two sensors before the turbo, the inlet air pressure sensor is immediately after the air cleaner element on the side of the top cover of the air cleaner near the front of the unit. Its sole purpose is to detect air cleaner restriction. Was going to contact crdjon about his ecm flashes to see if he has any useful information for me. Appreciate your input. Cannot find any other discussion about the inlet pressure sensor. If you find any others. please let me know. All my tests point to ecm problems.
Regards
John

GreenDieselEngineering · **Joined:** Sun Jun 07, 2009 5:10 pm **Posts:** 1111

Based on the data we have P0105 is a plausibility fault for pressure difference between the boost sensor in intake manifold and the air pressure sensor in the ecm.

The little pressure sensor on the side of the air box gives a fault code of P1189.

Do you have a monitoring tool that reads the boost and ambient air pressure? Measure with just the key-on and also at idle and see what the difference in values are.

gmctd · **Posted:** Wed Sep 24, 2014 11:23 am

You have an 'export' version for down under, which is somewhat unknown to us here in up over - your DTC P0105 is the BOOST sensor in the rear of the intake manifold, as GDE verified - ECM supplies +5v sensor supply voltage common to the BOOST sensor, the MAF sensor, the fuel pressure sensor, and the APP, so a supply problem would cast a DTC for all those sensors - this sensor ambiguity is prolly the cause of your dilemma over the troubleshooting steps listed in the manual

Check the BOOST pressure sensor, also know as the intake pressure sensor - it's prolly caked with oily carbon deposit which may have been compressed by BOOST pressure such that the initial output is incorrect for ambient BARO pressure - or the thermoplastic surrounding the sensor element could be compromised by the not within design spec coatings - or the temperature element resistance could have changed value indicating false temperature, throwing the pressure reading off - plausibility could be resulted from several things, so check it out......................

senatorjohn · **Posted:** Wed Sep 24, 2014 9:26 pm

The fact that your vehicles are different explains the confusion and lack of discussion on this sensor. The comparison between the barometric sensor in the ECM and the sensor near the air cleaner element only occurs around idle speed. Above idle, the situation is ignored. If I keep the rpm around 900, the fault code does not set. So it appears that it is this sensor that is at fault and not the MAF or the T-MAP( boost sensor). Sorry to bother you with a setup that does not exist on your vehicles.
Regards
John.

WWDiesel · **Posted:** Wed Sep 24, 2014 9:39 pm

If it is the pressure sensor on the side of the air box; refereed to by some as the the Mercedes sensor, this is the info on it:
IAP sensor - 05101120AB (pressure sensor on side of airbox)

gmctd · **Posted:** Wed Sep 24, 2014 9:57 pm

We do have that sensor, but iirc the ECM pings it only at key on for validation - I've slept some since then, but I was finding many errors in the service manuals, some in the reported DTC indexes - I had to go to the RAM CRD manual and the KJ Gasoline manual to clarify things - howsomever, just fer grins'n'giggles, have you pulled the BOOST sensor for visual inspection and subsequent cleanup?

senatorjohn · **Posted:** Thu Sep 25, 2014 7:12 am

In response to GDE, the codes I have appear to be different to yours. Very confusing. Do have a scan tool to read some values ( Autel MaxiDiag US703 and a few other numbers ) Did get the barometric pressure reading from the ECM , 10400 but not sure what units. Have not been able to find the reading again when I specifically went looking for it. Can also read boost and it seemed to be as expected, but will check again and learn a bit more about my scan tool. Will try another time. No such code as P1189 here in Aus. from the list I have in the 2006 shop manual. Very confusing.
thanks for your input
John

senatorjohn · **Posted:** Thu Sep 25, 2014 7:16 am

Reply to WWdiesel. That is the sensor and that is the part number. Have three of them, one new and two used. They all have the same pressure - voltage relationship when tested.
Regards
John

senatorjohn · **Posted:** Thu Sep 25, 2014 7:21 am

Hi gmctd.
Have pulled boost sensor and cleaned it. Seems to read boost ok when I checked it. Boost increased with engine load. Did not get the spare out of my 06 CRD, it is 700km away and I did not want inexperienced persons pulling that one out since it is a little more concealed.
Regards
John

mass-hole · **Posted:** Thu Sep 25, 2014 12:51 pm

senatorjohn wrote:

In response to GDE, the codes I have appear to be different to yours. Very confusing. Do have a scan tool to read some values ( Autel MaxiDiag US703 and a few other numbers ) Did get the barometric pressure reading from the ECM , 10400 but not sure what units. Have not been able to find the reading again when I specifically went looking for it. Can also read boost and it seemed to be as expected, but will check again and learn a bit more about my scan tool. Will try another time. No such code as P1189 here in Aus. from the list I have in the 2006 shop manual. Very confusing.
thanks for your input
John

that may mean 1040 millibar which is pretty much atmospheric pressure. I think the ecu reports it weird and adds that extra 0 but I could be wrong.

gmctd · **Posted:** Thu Sep 25, 2014 2:58 pm

The DTC conundrum is what I was referring to, but I've slept some since then so it's hazy - just fer grins'n'giggles, again, completely unplug the intake sensor-of-interest, see what DTC rears it's ugly head in that scenario......................

Sometime later - tho't I'd have some comparison data for you, but I've done everything I can thunk of to the li'l KJ butcept turn it over on it's back and tickle it's fancy, but cannot elicit a DTC for the inlet pressure sensor, not to be confused with the intake pressure, or BOOST pressure, sensor
- sensor in: BARO is 15psi, 3.81 volts
- sensor unplugged: BARO 1psi, 0.0 volts, no DTC
- rev the engine over 800rpm, no DTC

'Course, I do have the GDE hot tune onboard, so perhaps they coningulated that sensor's position in the grand scheme of things, eh ??

senatorjohn · **Posted:** Thu Sep 25, 2014 7:15 pm

Thanks mass-hole and gmctd. Will pull all sensor connections and record the dtc's. Contacted the crew in Aus that handle GDE tune and asked them if it was possible to switch off or modify the parameters of the circuit and the answer is "no". Whether they understood the question fully may be debatable. Will contact GDE in US for more info. after I get these extra codes.
john

senatorjohn · **Posted:** Fri Sep 26, 2014 7:03 am

Disconnected inlet air pressure sensor. The following codes appeared.
P1189 Chrysler cod according to my scan tool. No info on it.
P0069 MAP barometric pressure correlation.
P0105 Atmospheric pressure sensor. Previously stored code I think.
P1186 Inlet pressure sensor circuit

With the MAF alone disconnected, the following code.
P0069 MAP pressure correlation. May have left the odd word out here. Would expect same description as in the group above.

Could not get the barometric reading display I had previously but it appeared in other data as the same as before, 10400 at unknown units.
Will hopefully do more checks tomorrow
Regards
John

gmctd · **Posted:** Fri Sep 26, 2014 9:41 am

That verifies GDE's input
- your inlet sensor BARO and volts reads nearly same as mine so must be functional
- I have two major engine DTC's which I haven't done much to resolve and may be preventing the minor ones from logging
- I'm still leaning toward the intake sensor vs the ECM BARO sensor

The inlet sensor and the intake sensor should both read 15psi BARO, inlet @ ~3.8v dependent on your local altitude, intake was greater than 4 volts - I'll take some additional readings today

mass-hole · **Posted:** Fri Sep 26, 2014 12:20 pm

senatorjohn wrote:

Thanks mass-hole and gmctd. Will pull all sensor connections and record the dtc's. Contacted the crew in Aus that handle GDE tune and asked them if it was possible to switch off or modify the parameters of the circuit and the answer is "no". Whether they understood the question fully may be debatable. Will contact GDE in US for more info. after I get these extra codes.
john

There are certainly ways to eliminate a code from triggering. Our ECUs are the same and function similar too what is in Volkwagen Group diesels. As far as i know, there is a block of code within the ECU which lists out the different dtc code and assigns them a number which is used to determine what action is taken when that DTC is triggered. If you alter that number you can change how the ECU reacts to detecting a bad sensor, whether it is not turning on the CEL or whatever else you may want. I dont think the biggest issue is making the change itself, its locating the correct code block.

I dont know if this will eliminate the code all together, but it should turn off the CEL.

gmctd · **Posted:** Fri Sep 26, 2014 1:29 pm

Taken at key-on, then engine idling from fresh start, not at normal running temperature, as indicated by IAT :

Inlet Air Pressure IAP.............................15psi BARO 3.81v
Manifold Air Pressure MAP (BOOST)............15psi BARO 1.62v
BARO pressure ECM...............................15psi BARO 4.01v
Mass Air Flow MAF..................................1.81v
Intake Air Temp IAT..............................75.7deg F 3.69v (part of 4-wire MAP sensor)

Air inlet air pressuse sensor circuit disable

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