Don’t follow the fault code – follow the smoke signals
Repairing a DPF successfully means you need to follow the clues all the way to the source of the problem
Published: 14 November, 2019
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.
- Third Time Lucky
Today’s vehicle case study is a 2011 Vauxhall Insignia which came to us because of a loss of power. It had been looked at twice by another garage to no avail. As with every diagnostic job, we started by questioning the customer so we can gain as much background information as possible. After this initial phone call, I was confident of the type of fault being presented. This was confirmed at the subsequent diagnostic assessment. On running the global fault scan, we found multiple faults relating to the turbo system with ‘underboost’ and ‘overboost’ codes alongside DPF soot accumulation codes logged in the memory of the ECU.
We followed our industry-leading DPF assessment, learned through the DPF Doctor Network practical training programme. Firstly, using smoke testing we found the split intercooler hose (see Fig.1) which coincided with our P0299 turbo underboost code. However, the assessment does not finish when we find a fault. We see it through to the end. Further testing revealed that the vacuum control solenoid was not controlling the vacuum to move the turbo actuator which then mates up with the turbo overboost code stored. Using the serial data, we could see there was also EGR and air flow issues caused by running the engine with a boost leak.
Excessive soot and black smoke from the engine had choked the intake system and EGR valve. To tackle this mass of build-up soot and carbon we used the JLM Intake Extreme Cleaning Toolkit to break down the carbon. We removed the intake pipe and could see the thick ‘black death’ in the intake manifold (see Fig.2). As the chemical worked its way through, we could see on the serial data that air flow and DPF pressures were coming down. An endoscope was sent down the intake where we could see first-hand how well the intake clean had worked. We were impressed! This removed the turbo lag and flat spot at lower RPM.
Rectification
We went on to rectify the remaining faults. We added a bottle of JLM Extreme Clean to a full tank of fuel and took the car on the road to monitor some more live data and watch the Extreme Clean work its magic on the DPF system during regeneration. By the end of the road test the DPF pressures were down to single figures which is just what we would expect from a three-stage clean. To finish the job, we added a bottle of JLM Engine Oil Flush to the engine and carried out an oil and filter change to ensure any chemical from the intake clean was not in the engine’s vital organs (See Fig.3).
Our customer was absolutely delighted given he was expecting the worst after the previous garage had tried twice to fix. We use the Engine Oil Flush and an Emissions treatment on every vehicle we service. Customers always comment on the increased MPG and how clean the oil is after the flush has been used.
We have used JLM Lubricants’ products since we opened our garage doors in July 2020. I am pleased to report that we have never been let down by the quality and with the support received from Kalimex, UK distributors of JLM, Darren Darling, Founder of the DPF Doctor Network, or even JLM Managing Director Gilbert Groot. The support in our network is absolutely second to none.
JLM products used
Diesel Intake Extreme Cleaning Toolkit J02280 and J02285: This is a highly effective yet simple way to clean the entire combustion and exhaust system on a neglected diesel engine. With this low-cost kit you can quickly restore performance and reduce emissions. Developed in collaboration with diesel professionals including Darren Darling, the system delivers a controlled dose of powerful clean and flush fluids that gently decontaminate the air intake, combustion chamber, valves, injectors, and variable turbo vanes of a dirty diesel engine. No removal required. It is much more powerful than an additive added to the fuel tank or an aerosol air intake spray. Used with the two dedicated and chemically advanced cleaning fluids, each one addressing different contaminations to restore the original air flow to the engine.
Extreme Clean J02360: A very strong all-in-one blend of high-end chemicals to detox the entire fuel system including turbo, EGR and DPF.
Engine Oil Flush J04835: This gets the most out of new oil by cleaning out more dirt and contamination when changing the old oil and when used regularly, will not allow the build-up of dirt to develop again. It reduces fuel consumption and improves engine performance.
Emission Reduction Treatment J02370: A shot of this additive in the fuel tank will reduce the emissions and help to prevent a MOT emission fail or resolve a post-MOT emission fail. It also helps keep the exhaust and CAT clean.
For more information visit www.jlmlubricants.com and www.the-dpf-doctor.com
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