Half truth is lie.

initial miss fire DTC's

initial miss fire DTC’s

In the workshop recently we were presented with a BMW 1 series 116 petrol E87 model with a complaint of a hesitation under load or what can be described as a miss fire !

As always I initially interrogated the DME module (engine ECU) for DTC’s. I was presented with multiple DTC’S, SEE FIG 1 and so initially I decided to carry out a basic visual examination of the ignition coils and spark plugs.
The plugs did show early signs of spark erosion or corona ringing and the coils did look a little tired. On the strength of my visual examination I advised the customer to replace the coils with brand new genuine coils and NGK plugs with the proviso that we would need to carry out extended tests after fitting the coils.

I took the time also to clean the throttle body and realign using Autologic and simultaneously reset and fuel trim adaptation values.

Once reassembled I took the vehicle for a quick test drive approximately 6 miles which delivered an acceptable level of performance and didn’t present any dtc’s.
So I took the decision to finish the bill which included 1 hour diagnostic time at £85 +vat/1 hour mechanical labour £65+vat and 4 new Coils £25 x 4 and 4 new NGK plugs at approx £6 each. Total bill £268+vat. I’m not afraid to admit I held a little reservation in my mind to wether we had correctly identified and fixed the problem so I warned the customer about the lack of hard evidence and the chance that there might be intermittent faults still present which haven’t occurred during our test procedure but reassured him that what we have done for the cost is good common sense and the right place to start.
After a brief explanation of my findings and showing the customer the suspected faulty ignition components visually he paid the bill shook my hand and left.

It wasn’t until 2 days later he came back with what can only be described as a disappointed look on his face when he turned to me and said its exactly the same.

Not surprised by this I said ok let’s take another look offering the first hour diagnostic free of charge.

This time there were no fault codes present in the DME module, so I pressed the customer for more information and asked him to carefully explain exactly what is happening and he explained that the car would suddenly loose power and jerk violently whilst accelerating. Curious I took the vehicle for an extended test drive whilst carefully examining live engine data especially miss fire detected or (engine roughness) and only after 15 miles of driving the vehicle would do exactly what he described but I noticed the DSC light flash on for a brief moment so quick in fact I almost missed it. Eventually the vehicle would act up upon request at a certain load point normally acceleration out of corners or roundabouts.

I turned my attention away from live engine data and miss fire detect and closely examined DSC live data. All most immediately I noticed discrepancies with the two rear wheel speed inputs.
I quickly returned to the workshop to carry out a thorough visual examination of both rear wheel speed input sensors and pickups. The rear DSC speed input is taken from a ring attached to the drive shafts. Nothing initially looked out of place but when I examined a little closer and span the shaft I noticed an egg shape due to corrosion underneath the pick up. The sensor was hidden out of sight behind the shaft but it was clear the physical phonic wheel ring was distorted which would of course cause an error in wheel speed input to DSC !! Once the drive shafts were removed the evidence was clear and concise, the distortion in the shaft had actually caused physical damage to the ABS sensor.

2014-01-16 09.40.58 2014-01-16 09.42.03
The customer again was advised and quoted for the replacement of both rear drive shafts and sensors. I invited the customer down to inspect our findings and almost unbelievably he mentioned that he’d seen he DSC warning light flash on before but had completely failed to mention it. I always like finishing using my favourite quotes so he’s another one. Its actually a Chinese proverb but hey. ‘half truth, is lie’.

I always question myself and our procedure always tweaking and trying to perfect our diagnostic methodology and strive to deliver the best possible service and value for money. On this occasion it was no different but the fact remains the customer spent in excess of £250 + vat on a repair which didn’t fix the problem. Who’s to blame ?? Did I drive the car far enough? did I question the customer enough/ should I have carefully interrogated other systems on board before blaming the coils?? These are the questions we must ask ourselves in order to hone our skills and level of professionalism. All what I have mentioned above is up to debate and I welcome healthy debate. Personally I think I got it spot on and wouldn’t change my approach next time.

David Massey

ADS ltd.

For training information click www.ads-global.co.uk

By | 2017-05-11T12:27:12+00:00 February 19th, 2014|Workshop Blog|24 Comments

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  1. matthew horner February 19, 2014 at 9:46 pm - Reply

    David I think u got the repair spot on as u went about it the right way and fixed a potential problem further down the line 4 the customer and as 4 the dsc light I think it is up to the customer to give his or her mechanic all the right information but some time it does help go a test drive with the customer while they drive the car til the fault occur as driver patterns are all different oh and customer must pay 4 ur time in test drive

  2. Richard February 19, 2014 at 10:12 pm - Reply

    Think we all have been led down the garden path at one time or another with either components that need replacing before we can start to carry diagnostics or information the customer as failed or forgot to tell us , think you were spot on , love your work any discount on oscilloscope training courses? I’m in serious need of, thanks rich

    • Dave Massey February 20, 2014 at 8:50 am - Reply

      Hi Richard, Thank you for your comments I’m glad you appreciate my work. 🙂 Flattery will get you everywhere. please call Annette on 01772 201597 and she will do you an outrageous deal on scope and training.
      Kind Regards


  3. Darren February 19, 2014 at 10:43 pm - Reply

    We have all had issues like this I find it’s better to be safe than sorry. Clear down codes let the car go then tell customer to come back. In theory those misfire codes wouldn’t have come back. Every company different in there approach I don’t think there’s a right way however in a situation like this you know the customer won’t come back so maybe the question is how can you stop that

  4. Derek February 19, 2014 at 11:21 pm - Reply

    Hi Dave I have come across this a few times on BMW 1s and 3s, I had a customer who’s problem was that bad we disconnect the back sensors so he could drive the car home untill we had time replace the parts next day, the next morning we got a call to say the car wouldn’t start, after getting the 116i recovered we discovered the cas control system had a fault that no one had ever saw before (after contacting a few dealers and myself having working at a dealer for 20 years was getting know where) after further diagnostics I discovered the cas had picked up the rear sensors was disconnected would not allow the car to start as there was a fault in the dsc, expensive lesson learned

  5. Chris Glynn February 20, 2014 at 8:40 am - Reply

    I would have carried out the exact same approach, it’s unfortunate that customers fail to give the full description of when the fault occurs and any warning lights that are present. It’s almost as if they think the information they hold is irrelevant and that all we do as a technician is ‘plug it in and it tells us everything’, Thanks for the scenario and keep up the good work


  6. colin drissell February 20, 2014 at 11:15 pm - Reply

    from your findings it looks like you had two problems .plus the customer was not telling you every thing .
    the only think you could have done first time was print out codes for customer then clear codes then try car for your self before starting work.

    • Dave Massey February 21, 2014 at 8:13 am - Reply

      I’m more than confident that there were two problems and only through experience and advising the customer of further potential problems did I avoid any awkward confrontation. Despite not omitting the entire story the customer was incredibly understanding and happy to proceed with further testing and repair.

  7. Chris February 24, 2014 at 9:25 am - Reply

    This has just answered an unexplained problem from a few months ago. BMW X1 developed a similar problem after fitting an aftermarket speed limiter. As usual we were the last to work on the vehicle so got the blame (also the drivers hate the limiters) after disconnecting everything and driving the Car i noticed the same faults losing power under acceleration/ under load and DSC light flashing on. Drivers description of fault nothing like this. Anyway to cut a long story short the car was returned to Main Dealer as under Warranty and sent back a week later with no fault found. No reported problems since, but at least now i know the likely fault when it returns.

    Looking forward to more reading and helpful articles.

  8. Philip Rutt February 24, 2014 at 5:29 pm - Reply

    Hi Dave. Great case study as normal. Thanks

  9. Pete February 24, 2014 at 7:44 pm - Reply

    We have had this fault too. It took some finding! You would swear blind it was an engine management fault. Thank god for the DSC light. Reedley Service Centre Nelson.

  10. Logan February 27, 2014 at 10:30 pm - Reply

    I also agree you did handle this well. So to the point of your article: the issue isn’t your diagnostic methods. There may however be opportunity to improve information uptake during the service order process. Try to error proof and make it difficult for customers to lie.

    Customer information led you to assume misfire. The description hesitation under load was incomplete and not enough information to create an effective test method. With respect, maybe it would help to ask more questions than you are now. Consider a 5 why approach. Be ready to go 5 whys deep with your questions to get beyond customer perceptions.

    They need to understand because their modern automobile is such a technologically sophisticated machine you have to ask key investigative questions. So customers should also understand how complete information will keep them from returning to the shop unnecessarily by enabling you to properly root out their problem.

  11. Pete March 3, 2014 at 6:02 pm - Reply

    In my Renault days we got taught this. It’s called call dr c!

    Collect the evidence
    Analyse the evidence
    Locate the fault
    Determine and remove the cause
    Repair the fault
    Check the system

    A brilliant diagnostic strategy !!

  12. Roger March 19, 2014 at 12:50 pm - Reply

    Surely would have made sense to test the primaries/secondaries before replacing coils and plugs? Classic throw parts at the problem story

    • Dave Massey March 20, 2014 at 10:27 am - Reply

      Hi Roger, we always check secondary ignition using the scope and in this case didn’t show anything. The missfire was very intermittent and transient under load. The decision to replace the coils was based on our visual inspection of the ignition components for signs of wear and tracking.

  13. Karl myers January 5, 2015 at 7:40 pm - Reply

    So I have a 1 series which I have just bought,no engine warning light came on but car would hit 2000revs and judder violently,(limp mode?) it wouldn’t clear or go above 2000revs,so if I came to your garage with very similar symptoms to the customer mentioned can you explain why you couldn’t first try the cheaper option to solve the problem by replacing just the drive shaft ring an wheel sensor? Why a full drive shaft? And also you never explained if by replacing the drive shafts and sensors it cured the loss of power and violent jerking? I trained as a mechanic at Toyota for 3 years so have some knowledge,it just seems to me like instead of trying to cut costs down for this customer after charging him few hundred quid in the 1st place when it never solved the problem it was a case of new drive shafts end of,I live in Norway now and the garage did the exact same thing to me,common prob,2 new drive shafts and wheel sensors,that will b 2 and a half grand thank you!!!! No thank you,I’ll fit two sensors myself,piece of piss and replace the ring on the drive shaft 1st see how we get on!!!!

    • Dave Massey January 14, 2015 at 11:41 am - Reply

      Hi Karl, Thank you for your comments. Yes replacing the ring is one way of doing it I suppose but it won’t last. If you take the time to carefully examine the drive shaft you can see the cause of the ring catching the sensor is caused by excessive corrosion underneath the ring. Below I have stated what it would take to replace the rings and i urge you to think carefully which repair path you would take knowing all the facts.
      *sourcing the correct O/E rings with correct spacing.
      *remove the shaft
      *put it in a lathe to remove corrosion.
      *Clocking with DTI gauge for run out
      *Having prepared the surface
      *check for sufficient interference for the ring
      *press the ring into position carefully
      *clock the ring into position to make sure it’s true
      *at the end of all this you still have old worn CV joints
      *when it fails again repeat all of the above at the customers cost.
      The other thing to remember here is and I clearly stated there were two faults with this car not just one. After we had replaced the ignition coils the engine miss fire and related DTC’s had vanished but the car still suffered from a hesitation and drivability problem which ultimately led me to investigate the ABS system and find the other fault.
      Only last month i repaired a customers car which was namely a VW Golf mk4 GTI 1.8T which had suffered severe wiring corrosion on the top of the engine. Now then, I spent the best part of 6 hours carefully splicing the loom and replacing all the wires individually to save the customer on buying a complete loom and labour to change it which undoubtedly in your 3 years experience working as a Toyota technician you will appreciate the cost saved to the customer. I returned home that very evening at about 11:30 pm after staying late to complete the job to find out via facebook you can actually buy a mini sub loom replacement part which isn’t on any of the VAG part catalogues and comes from a specialist supplier. Upon finding this information out I immediately ordered the correct part and gave my customer a complete refund having lost 6 hours of my time of which I’ll never see again and was no fault of my own. I ended up fitting the sub loom and billing an hour of my time. I think this tells you a great deal in the professional way in which I approach jobs and charge for my time.
      Despite my 17 years experience I don’t know it all in fact I know very little and each day I’m learning and always striving to better myself and offer the best advice and value for money service money can buy. If you ask any of my customers the will reinforce this statement.
      I can promise you this Karl, if you come across anybody who is more conscientious than me when it comes to offering good advise or value for money then please let me know, I’d love to meet the man and shake his hand and offer him a job.
      You can only build quality into a Job, but you can’t add it later.

      I eagerly await your response.


  14. Tony Young January 19, 2016 at 1:47 pm - Reply

    I have a BMW 1 series with a similar problem, dtc light flashing slight misfire and abs cutting in particularly on a rough road or when exiting left hand bends, I took the car to two different workshops for a diagnostic test they both came back with a similar diagnosis ie ignition or fuel problem. I am a retired aero engineer who has always worked on my own cars over the years as well as building and racing motorcycles and feel I have a reasonable engineering background.I was convinced that the problem was in the movement of the rear suspension.I eventually contacted a local independant BMW specialist to discuss the problem he chuckled when I told him about the diagnosis and said the problem was almost certainly the rear drive shaft reluctor rings/sensors. The car is now in my local garage for new rear driveshaft.
    Tony Young

  15. graham January 19, 2016 at 7:09 pm - Reply

    Hi, I recently bought a 2004 118D that had the ABS warning light on. when i read the codes it said front right sensor. Bought one but when i went to fit it today the original one wasn’t connected. I reconnected it and took it for a drive which cleared the ABS light on the dash but it went into limp mode (bunnyhopping under accaleration at around 2000rpm) i tried the new wheel speed sensor but the problem was the same. Disconnect the front drivers side speed sensor and the car drives fine but the abs light stays on.
    Woud i be correct in assuming the fault lies with the front drivers side hub or does disconnecting one sensor disable the entire ABS system?
    I will take it for a drive tomorrow to see if i can notice any discrepancies in the live data.
    Any help/advice would be much appreciated.

  16. Minde April 28, 2016 at 12:26 pm - Reply

    We had same one coming from BMW dealer – guy was offered new air mass meter costing little over £1000,- parta and labour. He decided to try aftermarket one to find out that it made no difference. Now when he came – one of his run flats was holding 0.5 bar of pressure. When questioned – client confirmed he saw DSC light flashing briefly when he was experiencing juddering and power loss.

  17. Peter August 17, 2016 at 2:31 pm - Reply

    As a newcomer to BMW with a 1-series 116 (8 years old and only 47,000 miles) I’ve just been stung by the same problem – intermittent flashing DSC light + jerk of brake application and engine misfire to reduce power AND tyre pressure alarm, which both run off the same driveshaft speed sensors. I’ve rebuilt classic cars for ages so I knew what to look for. I think the first comment here is fine – they had no clear evidence of a fault and did appropriate repairs. The fault lies with BMW for devising such a STUPID and complex system which can break down so easily yet not report it for diagnostics… I had a 18 year old Jag XK8 with the same sensor system – one sensor failed which I could replace easily myself but the serrated driveshaft rings were absolutely sound after 140,000 miles..! I also had several other faults with the BMW in different systems. Being new to BMW I’m really disappointed that a supposedly quality manufacturer can build-in so many poor components and with so many bells & whistles that things inevitably go wrong.

  18. Big Mick November 20, 2016 at 11:48 pm - Reply

    I had the same problem with my BMW e90 320d the driver side rear driveshaft reluctor ring distorted with corrosion and rubbing the speed sensor causing all the forementioned problems above when going around right-hand bends and roundabouts, I removed both driveshafts and replaced both reluctor rings and sensors on both driveshafts this did indeed cure the problem for now.

    My thoughts are I will never own another BMW as I have owned this car for 3 years and the first week of ownership I had to remove the dreaded swirl-flaps and install banking plates as to avoid the common failure of the flaps destroying the engine.

    And don’t forget the engine timing chain failure on the N47 diesel engines this is disgusting design flaw by BMW.
    And now turbo fail problems.
    The new BMW have plastic electric water pump failures.
    This is disgusting design flaws by what is supposed to be a quality car manufacturer.
    I am done with BMW.

  19. Phil February 4, 2017 at 5:23 pm - Reply

    OMG you are AMAZING. I sold my sister my 2008 116i, its had nothing but problems. ECU sent of twice, spark plugs, Coils replaced under recall, Injectors and MAP thermostat sensor what was a nightmare to replace AND STIL!! this piece of garbage still judders. OBD said it was this cylinder then that cylinder. I just went out and pressed the DTC button and guess what? Yes you genius this is the problem. I think BMW have employed the best of the best team to program their cars so we buy everything but what we need? THANK YOU.

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