Member Since: 16 Jan 2014
Location: Queenstown
Posts: 3
P0100 MAF error code
Please bear with me, this is my first post and typing on a smartphone. I have a 2007 D3 2.7diesel and the EML dashboard light is on. I took it to a local garage and they used an autologic scanner and confirmed P0100 code. I've replaced the MAF sensor but the code reoccurred once cleared, so a friend lent me another good MAF, same symptoms again. However I've noticed the EML light and code keeps returning on the third start of the engine.
If I erase the code with my reader, it clears the dashboard EML and the code. I can then drive the car without the EML light or code returning. However when I stop and turn off the engine, on the second restart the EML light and code comes back. If I park the car in my driveway, clear the code and restart the engine without moving, the light and code consistently returns on the third restart after clearing the code.
As you can imagine I'm baffled. If the MAF sensor is good you might suspect an electrical fault. If that's the case I would expect the light to come on after every restart, or randomly. The fact that it's every third restart suggests it some logic. I appreciate that there must be some starting diagnostics that obviously checks all the systems, but fail to see why it detects the fault every third start. Once the EML is on it will stay illuminated until reset.
In trying to diagnose the problem I've already read a lot on this forum about EgR values (which mine are not blanked yet), as the car is also very sluggish below 2000rpm. I tried running the car with the MAF sensor disconnected but that doesn't appear to make any difference. I'm getting approx 38mpg on a long run at about 60mph. So totally confused.
Would appreciate any advice.
8th Aug 2014 8:23 am
Robbie
Member Since: 05 Feb 2006
Location: ¯\_(ツ)_/¯
Posts: 17932
On a 2007 or greater a failed EGR can trigger the EML. With your symptoms I would start looking at an EGR diagnostics and a potential solution (replace, emulate or software).
What we do not know is how good the scan tool is at your local garage as it may only be able to read the simple generic 4 digit code. Checking with a known good scan tool may help as would using a tool with live data so you can see the EGR commanded and actual positions.
Live data would also allow you to see the mass air flow detected by the ECM. You can test the MAF and wiring with a DMM if that is still of concern to you. This is on my D4 which has 2 MAFs, but you get the idea:
Click image to enlarge
Click image to enlarge
Land Rover - Turning Drivers into Mechanics Since 1948
Measured the MAF sensor pin as suggested and I get +4.5V[img]
I have a simple Autel AL319 scanner that can display limited live data. This is what I get at 1500rpm.
I take your point on the EGR's, but I can't understand why a mechanical device would consistently fault on the third start. If it was everytime, or even random it would make more sense.
9th Aug 2014 5:57 am
Disco_Mikey
Member Since: 29 May 2007
Location: Dundee, Scotland
Posts: 20857
The MAF sensor code is stored, due to an incorrect airflow reading, if one EGR is sticky.
When the valves are closed, the ECU expects a certain reading. If this reading is different, the light will come on
Need to have the valve command and actual positions checkedMy D3 Build Thread
Member Since: 05 Feb 2006
Location: ¯\_(ツ)_/¯
Posts: 17932
Mike, with the code set are you expecting a zero reading from the MAF as I don't recall seeing that before (admittedly I would be looking at actual EGR position so I may have missed it)?Land Rover - Turning Drivers into Mechanics Since 1948
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