No code; No problem?
Recurring DPF problems but no fault code? Sounds like a job for Darren, that’s for sure
Published: 30 January, 2020
By Darren Darling
The challenge: A 2009 VW Golf 2.0 TDI with recurring DPF problems and no fault codes stored.
This low mileage Golf was presented to us after an unsuccessful trip to the main dealer where the customer was told there was nothing wrong with the car. The customer’s complaint was that the DPF warning light would illuminate every 100 miles; MPG was poor and the car was smoking excessively during regeneration (white smoke). As always, we carried out a thorough assessment of the vehicle to find out why the car was having these issues.
I suspected that the lack of any fault codes was the reason the owner was told that the car was fault-free but clearly we had an issue as the car should not be in regeneration so frequently. We quickly determined this was not caused by a blocked DPF as the DPF was very clean and there were no mechanical issues with the car.
Extended road test
Our next step was to carry out an extended road test while recording live serial data. If the customer had predicted correctly then we would see the DPF symbol illuminate in the next 20 miles or so. Sure enough, the light came on during the road test and the vehicle initiated DPF regeneration. This now gave us an opportunity to monitor the car during regeneration to see what was going on. We noticed that our temperatures during regeneration were too low and that the car did indeed smoke very badly.
Because of the low temperature, the duration of the regeneration was also excessive, taking over 40 minutes to complete. This is not uncommon and we have seen this caused by a software issue on many occasions. We then consulted our database and could see this exact problem with the software version so our next step was to carry out a software update and repeat the extended road test.
The car was noticeably smoother and quieter following the update but it did not initiate regeneration. Although a good sign, we had not seen any evidence yet that it had improved. So, we headed back to the workshop to carry out a forced regeneration so that we could monitor temperature, smoke and regen duration.
We were now happy with the temperatures; the excessive smoke had gone and the regen duration was back to normal. We were confident that the software update had fixed the car.
This job highlights the need for the independent workshop to invest in the correct tooling to carry out software updates because they are becoming more common. No unnecessary DPF cleaning was required to sort this DPF problem out and no parts were fitted to the car.
Another job done and another happy customer.
- No codes, no clues?
Have you ever had a car in with a running fault or an issue, and you plugged the diagnostic tool into the OBD socket then read for trouble codes, only to be met with the message ‘no faults stored’?
For many reasons, this confuses technicians and stops them being able to progress with the job. They have no clues or starting point to work from. However, many other tests can be done to find the root cause of the issue. I have worked with many a technician who has been lost after finding a ‘no fault found’ message. I recently had a job where I was able to demonstrate to my colleague how knowing some numbers and how systems work and interlink can help identify what is wrong.
Call-out
The vehicle in question was a 2012 Land Rover Discovery 4. As we specialise in LR we have built up a good reputation in the area for being able to fix them, having also invested in dealer tooling and information. The customer’s first contact with us was via telephone and he explained he had parked the vehicle up outside his house and then having come to it the next day it would not start. The engine would turn over but it would not fire into life. He informed us his local garage had come out for a look and had been unsuccessful in finding the cause and recommended getting the vehicle recovered to us. He asked our call-out charge and asked for us to come and take a look before he organised recovery. This is not my favourite type of job as with limited tooling there is only so much you can do but we agreed to go and take and look and see what we could find.
No fault codes stored
Along with my colleague Jamie we went to the customer’s house that afternoon, taking a scan tool and the tool kit in our work van. Once we arrived we spoke to the customer to gather some information about the problem. He told us no recent work had been carried out on the vehicle and the other garage had done some basic tests on the battery and fuel system where it sat but could not find an issue. I sat in the vehicle and cranked the vehicle to verify the complaint, doing this also allowed a few checks to be done by listening to the sound of the engine cranking. A trained ear can pick up a compression issue, whether it is spinning fast enough or anything mechanical which doesn’t sound correct.
On this vehicle though all sounded ok. I then let Jamie do some checks to see what he could find. As a younger technician he mainly does MOT and general service work, so it was a good opportunity to possible teach him something along the way without the distraction of a busy workshop. After some basic checks he decided to plug in the scan took and see if any fault codes were stored. Upon carrying out a fault code report he was met with the message ‘no fault codes stored’. I then asked him what his thoughts were and where we go next. His reply was “I don’t know?” I am sure this has happened to some of you reading this article, we have all been there.
Live data
I explained to him that live data was a key element here and we should use it to our advantage. We need to look for data relevant to the complaint to rule out what it can’t be, and knowing what the numbers mean will do this quickly. Unfortunately, this takes years of looking at good data, taking notes and memorising it. Luckily for him, I was able to assist. My first checks were to be engine RPM, fuel pressure, immobiliser status, cam/crank synchronisation and a plausibility check of all temperature and pressure sensors to make sure they were in spec. Working through them all with ignition on, then cranking everything looked good so the engine should start but why wouldn’t it? This is where it pays to step back for a moment and evaluate what you know already and what you should do next.
Smoke/air pressure
An engine in its simplest form is an air pump. We know it needs compression, fuel and air to run. With what seemed to be good compression, and from what I had heard, also good data from the scan tool, with limited resources, I decided the next test would be to see if any smoke was being emitted from the tail pipes. This would show if there was any sign of fuel delivery to the engine. With good RPM and fuel pressure, if the ECU is happy, it should be firing the injectors. There was no smoke, however when I felt the tail pipes there was no air pressure whatsoever from either tail pipe. Was this a clue to where the issue may lie?
My first thought was we have a restriction and the engine cannot breathe, so we are missing the air section of the triangle for the engine to run. I then had a good visual inspection of the engine. Knowing the design well, I decided to open the inlet up to atmosphere by removing the map sensor to see if there was any change. If there was a blockage, this test would prove it and allow the engine to run. In this vehicle, the engine is a V6, so it uses a conventional V configuration. To allow air to flow into both intakes of each bank there is what Land Rover call an intake throttle manifold which also houses the MAP sensor, the EGR inlet pipework and a throttle butterfly flap with a rubber hose to direct air from the intercooler into the manifold (fig1). Removing the MAP sensor would allow air to be released if there was an issue from either EGR valve or upstream from the intake i.e. throttle butterfly, failed turbo just to name a few. On removing the sensor and cranking the engine it now fired into life and idled fairly well, this confirmed we had a blockage somewhere manifold side starving the engine of air.
Throttle butterfly flap
Checking the clock, we still had some time left allotted for the call out. I decided as it was easy to remove the intake hose to the intake throttle manifold just to see as a quick test if the issue was before or after. Upon removing the pipework and refitting the map, the engine no would not start, again proving the issue was on the engine side of the pipework. Removing the air intake plenum to the throttle manifold then revealed the issue. The throttle butterfly flap used to strangle the engine of air on shutdown had jammed shut and never reopened as the housing was heavily covered in carbon. This butterfly, when working correctly, should spring back open ready for the next engine start. Questioning the customer and his driving style revealed he mostly done slow speed and town driving and used supermarket fuel, all of which were a contributing factor to the issue as the valve sits closely to the flow of EGR gas from both valves. Forcing the valve open and refitting the components allowed the vehicle to be driven back to the workshop for a repair to be carried out.
Upon the removal of the entire assembly (fig2), it was found the unit would be better to be replaced as cleaning would not remove all of the carbon deposits and could cause the issue to re-occur. The EGR pipework was also removed and cleaned as a preventive measure along with an oil and filter change and the vehicle was returned to the customer.
Further learning
Why were there no fault codes stored you ask? Well on this engine the position off the butterfly flap is monitored and it should have stored a stuck closed fault but this may not be part of the software’s strategy so I am unable to answer why. However, this article shows that if you have an issue and no faults are stored, there are tests you can do to find the issue. So next time you have a scan tool connected, grab for example 10 good live data PIDs and store them then learn them off by heart. Once you have mastered that section move onto some more and soon you will build up a good mental library of what good data should be, which helps massively to fix cars!
- Don’t follow the fault code – follow the smoke signals
When this 2010 Vauxhall Insignia arrived at our workshop recently, we were asked the common question: “How much to clean my DPF?” As always, we informed the customer the first thing we needed to do was to undertake an assessment, so we could determine why the car was having DPF problems and what was required to fix it. This assessment is much more than a fault code read, often perceived as a ‘diagnostic check’ and this highlights the difference. The fault codes present on the car were ‘P2453 DPF Pressure Sensor A Circuit Range Performance’ and ‘P2458 Mass Air Flow Sensor Performance’.
Opening the bonnet, we were not surprised to see a new MAF sensor and a new DPF pressure sensor. This is frustrating as the owner has paid for these unnecessary parts to be fitted on the basis that ‘the computer said they were faulty’.
Looking at the DPF pressure sensor fault first, the ECU was reporting a circuit range fault. This may look like a faulty sensor but is in fact caused by excessive DPF pressure. The pressure is measured by the sensor. The signal is sent back to the ECU as a voltage so the excess pressure causes an excess voltage signal and in turn the ECU reports what it can see. The DPF back pressure was in excess of 150MB at idle indicating we must clean the DPF after addressing the cause of the problem.
Moving on to the MAF performance fault. Again, the ECU only reports what it sees as incorrect; in this case incorrect air flow. This is obvious when analysing live serial data so our next step was testing the intake system for leaks to confirm our suspicions. As you can see there was a significant leak from an intercooler pipe. We found a cause for both issues. The split pipe would have initially caused the MAF fault but in turn would lead to the DPF pressure sensor fault due to the excessive soot being produced with the major boost leak.
After consulting the customer, we repaired the car, replacing the intercooler pipe. Root cause now taken care of we had the easy part – cleaning the DPF. Our weapon of choice for DPF cleaning is always the JLM Lubricants’ Clean & Flush. With the step one chemical we left it to soak for a few minutes. After running the engine for a few minutes, we flushed the DPF out with the step two JLM DPF flush.
After the clean we had a healthy 6MB of back pressure in the DPF and the pressure sensor fault was cleared. An extended road test confirmed the fix.
- DPF maintenance
Achieving the tough vehicle emissions levels under Euro 5 legislation requires a Diesel Particulate Filter (DPF) to be fitted to collect carbon soot particles generated from the combustion process in a diesel engine.
- JLM Academy launches with DPF Doctor founder Darren Darling at the helm
The JLM Academy officially opened its doors on Saturday (20 July). The brainchild of Darren Darling, founder of The DPF Doctor Network, the new Academy is fielding a top-drawer roster of industry trainers, including Darren and Andy Savva, a.k.a The Garage Inspector.
- Launch UK - New PRO 4 diagnostics tool
X-431 Euro PRO 4 is a new diagnostics tool from Launch UK. The 1.4 GHz Quad-Core product is based on the Android operating system, and supports American, Asian and European passenger car and light commercial vehicles. It comes complete with a protective case and docking station, connectors and printer. The product also comes with a two-year warranty and two years’ worth of free software updates. Key features of the PRO 4 include: Manufacturer reset and service functions, service light/oil reset, OBD II functionality, live data graphing and, the ability to save, share and print report sheets. Additional functions enable technicians to carry out automatic VIN recognition, new battery registration, ABS brake bleeding, DPF checks/regenerations, tyre pressure monitoring, module programming and recoding and, key coding/matching. The PRO 4 also has WiFi and bluetooth connectivity meaning monthly software updates are done at the touch of a button. Battery capacity stands at 7000 mAh and usage time is eight hours on a full charge. The 10.1 inch screen tool includes 2GB of RAM and a 5.0 mega pixel rear camera.
