1997 QX4 MAF Question - Code P0105

[woa26927]

Hi there,

First off I would like to say this is my first post. I am impressed by the knowledge and dedication of the NICO members. This is a great community. My question is regarding my 1997 QX4. I have approximately 185,000 klms on the vehicle and now have code P0105 - Manifold Absolute Pressure code. The dealer suggested that I replace the MAF assembly. I replaced the assembly myself at a cost of over $600. The code returned moments later. Is there anything else that I should be looking for? i.e TPS, leaks, etc. I have also read some information with respect to relearning the idle. I am not sure what that means or how to do it. Any help would be greatly appreciated. Thanks in advance.

Wes

[Q45tech]

Think about the code and what it said! Why did you replace MAF when the MAP assembly is at fault. MAP sensor measure plenum pressure against the earth's supercharger [14.7 psi] as a reference.

Idle 20" HG is ~= [20/29.92=] 9.8 psi in plenum as the throttle is opened the pressure rises progressively to maybe 13.8 psi at WOT 4,000 rpm.

FSM fully describes.

A triple check on the TPS, IAT, and MAF signals. All things nust track with rpm to create the load signal.

"The MAP sensor is then used for rationality checks and to test the EGR valve. The way they do this is during a deceleration of the vehicle when there is a high vacuum present in the intake manifold. During this high vacuum the PCM will open the EGR valve and then monitor the MAP sensor values. If the EGR is functioning properly, the vacuum in the manifold will drop as exhaust gases enter." from http://en.wikipedia.org/wiki/MAP_sensor

http://autorepair.about.com/li...b.htmh ... so...1mp/1

[woa26927]

Thanks for your reply and explanation. The reason I replaced the MAF assembly was that two different dealers told me that the 1997 QX4 engine does not have a MAP sensor and it would be the MAF triggering the code. It definitely sounds like they were wrong. After reading your reply yesterday I checked with three other dealers and they told me the same thing....no MAP sensor in the engine.

Can you please let me know what I should check from here? EGR valves, vacuum lines? Your post noted that the MAP assembly is at fault. If the engine does not have a MAP sensor how do I go about testing the assembly? Thanks again for your help. It is greatly appreciated.Wes

[Q451990]

I downloaded your FSM (Factory Service Manual) and the sensor is there. Go here and download your FSM. http://phatg20.net/index.php?o...id=14

You will need to google for a utility to decompress the .rar file into a .pdf

Then check out pages EC-106 - EC-112. I would guess that you have a corroded connector or leaking/disconnected vacuum hose somewhere, but that's just a wild guess.

Good luck!

Heath
Modified by Q451990 at 12:09 AM 11/7/2007

[woa26927]

Thanks for the manual and the info Heath. I will check it out tonight and report back tomorrow. Thanks again.

Regards,

Wes

[Q45tech]

After the download and deraring check section EC-106 for full PO105 diagnosis.

Sure shows you cannot assume a service writer knows anything about cars.

Nice drawings showing MAP and all.

Never assume a EVERY or the bulk of dearlership are 100% qualified to repair a vehicle.

Why NICO exists to help owners become more educated than typical dealer techs.

The problem may be that Nissan calls it ABSOLUTE Pressure Sensor not MAP. [Manifold absolute pressure]

[woa26927]

Thanks. I plan to take a look at the section, drawings and vehicle when I get home this evening. It has been an expensive lesson for me. Traditionally I don't trust dealerships...I don't know why I did this time. I wish I found NICO prior to investing in the parts.

The knowledge exchanged at NICO is amazing!

I can't wait to troubleshoot and hopefully resolve the problem.

Thanks again.Wes

[Q45tech]

By chance we had a 97 QX4 come in for a starter and a radio antenna. There was a beautiful MAP sensor between the MAF sensor and the PS reservoir.

[Q451990]

Q45Tech, Any chance it's different on Canada models?

Wes, hopefully you saved your old MAF. It's always good to have spares - especially if it's the same one on both of your QX4s.

Heath

[woa26927]

Hi Heath,

I was successful in opening the files. Thanks so much. They are a great resource. I have read the section and reviewed the illustrations.

Unfortunately I did not have an opportunity to look at the truck last night. It was after 11 when I finished and it was raining buckets - the truck is parked outside. I plan to take a look tonight.

I did keep the old MAF assembly. I have been doing some reading and some posts state the idle must be "relearned" after the MAF is replaced or the vehicle may possibly run rough or throw another code. Is this true on all vehicles? If so can you please let me know how to carry out the relearning procedure.

If the location of the MAP sensor is different on Canadian vehicles is it safe to assume that it will still look the same? Hopefully it is not too difficult to locate.

Sorry for all the questions.

Thanks to yourself and Q45tech for sharing your time and your knowledge. It is greatly appreciated.

Regards,Wes

[woa26927]

Hi there,

I replaced the MAP sensor this weekend. It was so easy to find based on your help. Thanks a lot. The sensor was actually stamped "Boost Sensor"...I cleared the code and the SES light has been off ever since. I can't thank you guys enough.

Kindest Regards,Wes