 | Home > Puma (Tdci) > MAF Error and limp mode |
 
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| AMBxx Member Since: 24 Jul 2016 Location: York Posts: 996   
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After 500 miles at 60-70mph, my 2.2 Puma's engine warning light came on and went into limp mode.
I plugged in an ODB reader. 2 errors, one relating to the MAF, the other to the turbo. I've lost the search history on phone browser, so don't have the error codes. I reset both errors and have driven another 150 miles without problems. I filled up with Shell Super before the journey and topped up with Asda (all that was available) after 220 miles. Not sure if either of these could be the cause. It's happened twice before, but before I had a reader. Once when just 12 months old, the other time last year during a terrible storm. I'm sort of assuming (and hoping) that the turbo error is related to the MAF sensor. Assuming it is the MAF sensor, is there anything I should do with the minimum of tools if it happens again? I'll be in Orkney tomorrow, so don't want to risk breaking anything. Also, should I be heading to a garage to get something fixed/cleaned? |
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9th May 2024 8:14pm |
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| Martin Site Admin Member Since: 02 Apr 2007 Location: Hook Norton Posts: 6492 
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Will be depend on the exact codes, but a MAF reported code could be split Intercooler or hose, or loose hose.
Everyone loves to jump on these sorts of faults as being a faulty MAF, as that’s the component in the error. However the code means the MAF signal has triggered a plausibility error. For example, if it says “signal amplitude too high” for the MAF signal, it means the ECU has worked out that at that engine operating point, the value of airflow being sent from the MAF is higher than it expects. So it means extra air is passing the MAF, which typically means a leak out on the pressure side of the turbo - post compressor (eg Intercooler or hoses as above). If it said “signal amplitude too low”, the MAF is reporting less airflow than expected. This generally means a leak in before the compressor, so the engine is receiving “unmetered” air. So it’s not typically pointing to a faulty MAF.  1988 90 Td5 NAS soft top
2015 D90 XS SW |
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9th May 2024 10:22pm |
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| bear100 Member Since: 22 Mar 2010 Location: South Wales Posts: 1874  
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Sorry to hijack the thread, you mention lost search history, is there a list of error codes available?
handy to have  2016 Range Rover Autobiography 4.4 TDV8
2010 110 XS Utility 2.4TDCI 2010 Range Rover Sport TDV8 (gone) 2007 Discovery HSE TDV6 (gone) 1993 110 csw 200 tdi (gone) 1994 90 HT 300 tdi (gone) 1994 discovery 300tdi (gone) 90 hybrid 3.5 v8 (gone) Range rover bobtail 3.5 v8 (gone) |
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10th May 2024 7:37am |
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| mwestcrew Member Since: 09 Dec 2019 Location: South Warwickshire Posts: 222 
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Wise words from Martin. I think a lot of people see MAF on a fault code and immediately order a new one.
Doesn’t help that the fault code descriptions are a little “ambiguous”. Can’t think why manufacturers might do that……..  2011 130 Utility Body
2005 110 Van |
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10th May 2024 8:32am |
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| andy63 Member Since: 30 Jun 2023 Location: north east Posts: 283 
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It should be possible to check any sensor or actuator with a scope to determine if working as it should.. Ie it's supply. Ground and signal or switching.. As Martin has said plausibility faults can be checked and investigated to see where they lead, but it should be possible to check that the outputs confirm the code generated..
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10th May 2024 12:52pm |
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| PRENT1 Member Since: 02 Sep 2015 Location: bromley Posts: 42 
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I had a very similar issue when i was driving back from France.
It turns out i had split on of my turbo hoses. an easy fix and reset and been good since. |
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10th May 2024 1:17pm |
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| AMBxx Member Since: 24 Jul 2016 Location: York Posts: 996
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I think the errors were p0101 and u0401.
Ran fine today but didn't drive as much. |
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10th May 2024 4:32pm |
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| andy63 Member Since: 30 Jun 2023 Location: north east Posts: 283
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Well it's my turn now😩😂
Drove back from Ireland yesterday with no issues but did about 40 miles this morning and the management light and limp mode came on.. Pulled in and checked the codes.. The glow plug I know about but it was the dreaded mass air flow😩 Had a quick check but couldn't spot anything obvious.. Cleared it and as soon as I pulled off it was back... Nursed it home in limp and will have to check the intake side.. The codes as someone mentioned are a bit ambiguous.. Funnly enough I had planned to fit the alisport induction system anyway🤣 Click image to enlarge |
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12th May 2024 11:44am |
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| andy63 Member Since: 30 Jun 2023 Location: north east Posts: 283
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Well the only thing I could find after removing the air box and engine breather hose was a loose clip in the turbo outlet..
The hose was still well pushed on to the spiggot outlet just the clip was slack.. I've tightened that up and all appears good.. I can't follow the wording of the above fault code.. Its on about general electrical failure and voltage over threshold.. As far as I know the maf on mine is digital and the voltage level is fixed.. Its the frequency of that switching voltage that relates to air flow.. Anyone know 🤔 Anyway I should be grateful it appears to be sorted.. |
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12th May 2024 1:41pm |
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| custom90 Member Since: 21 Jan 2010 Location: South West, England. Posts: 19663
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Are you using Genuine air filters? And is the water separator removed?
Finally, is there a RAI or Snorkel? I’ve always used standard intake or Safari, genuine air filter and water separator removed. It has been known for some with a RAI to get a nuisance MAF DTC. Removing the rain separator and cutting out the airbox inlet at the base IS well worth doing, as well as fully sealing or replacing the ducting completely. I have had the rain separator out years, and the airbox entry cut out towards the base, I’ve driven in all conditions in the heaviest of rain and never had any slightest issue with damp or air wet filters so that is a non issue. It just adds more restriction. Bi annual cleaning of the MAF with an aerosol MAF cleaner (or Brake cleaner) is worth doing, you don’t touch any element, just spray it through in the correct direction of travel. Leave it to evaporate on a clean bit of paper towel and refit just like the MAP sensor cleaning process. The important thing is just don’t touch the elements in any way, just rely on the pressurised spray only. Only really needs doing at service time, no more often than that, but if you don’t do it yourself most garages won’t, just like they won’t do Brake or clutch fluid either. (Not included in servicing). You might think it would be done but isn’t commonly. For example brake fluid should not have a moisture content about 4%, and it starts to get towards that around the 2 - 3yr mark as it’s hygroscopic and takes on / absorbs water over time. That is more compressible and also allows temperatures to increase higher and the greatly increased likelihood of boiling the brake fluid leading to severe brake fade. Particularity dangerous on a long hill decent under load. Back on topic, be sure to check that the wires entering the MAF connector aren’t split. It can be worth once a year, opening the air box, just to clean out the base of it, and clean off of the element gently the year between replacing or change it each year. But, you’ll be surprised what gets in there. Whatever systems you have I would remove that rain separator, and carefully cut out the airbox base inlet being careful to ensure the airbox exterior is fully in tact of course. An old soldering iron and or a dremel is ideal, be sure to clean up any dust and put a disposable glove over the inlet if you take away the airbox lid, that way you won’t get any dust in the inlet hose and can keep the lid and MAF safely out the way in a plastic bag to keep it clean. There is a small gain in performance in my option, it allows for better inlet airflow without restriction. Same with exhaust, there isn’t a need for silencers they just cause restriction, after the CAT which should be in place, the mid and rear silencer just disturb the exhaust gas flow, keeping heat levels higher, and reducing performance by restriction. Restriction, just reduces performance and MPG for no good reason, and scatters air input or gas flow output which impedes performance and responsiveness. Diesel$ Live$ Matter. ⛽️🛢️👨🔧🧰⚙️ RED, WHITE & BOOST! 🇬🇧 |
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12th May 2024 2:38pm |
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| andy63 Member Since: 30 Jun 2023 Location: north east Posts: 283
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Cheers.. I've not had any issues till today..
And as I said above I intend doing the alisport intake upgrade.. Had the bits for a good while, but never got round to fitting them yet.. Still curious about the wording of the fault code.. As I said above the ref to voltage threshold seems odd given it's a digital sensor and the air flow is signalled by the switching frequency.. I read a lot about cleaning maf sensors and I have done myself, but the hot wire type sensor can have a sort of self cleaning cycle.. Or so I've read... I'll attach the screenshot of the bit I'm on about.. Click image to enlarge |
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12th May 2024 3:21pm |
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 16944 
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I think you'll find that the analogue air reading is sent as a PWM signal to the ECM where the PWM signal is integrated back to an effective analogue DC equivalent. This could quite plausibly be higher than the expected value for a particular set of conditions. |
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12th May 2024 3:52pm |
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| andy63 Member Since: 30 Jun 2023 Location: north east Posts: 283
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Ta.. I'll do a bit more checking.. But the output from my maf sensor is digital.. Ie it's a switching voltage from around 5v to 0..and it is the rate of switching that signals to the ecu the mass of air flowing..
Been digital it saves the ecu the job of converting an analogue signal of varying voltage to a digital signal.. That's my take on it atm👍.. |
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12th May 2024 4:08pm |
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| Martin Site Admin Member Since: 02 Apr 2007 Location: Hook Norton Posts: 6492
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That may well how it works, but the OBD2 code (which is a mandated industry standard code) relates to signal amplitude.
So it must convert the digital signal to the equivalent amplitude for diagnostic purposes. 1988 90 Td5 NAS soft top
2015 D90 XS SW |
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12th May 2024 4:18pm |
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