Third Time Lucky
DPF Doctor, Chay Blyth shares his experiences with a car he was presented with after two previous fixes elsewhere had failed
Published: 04 May, 2021
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
- No code; No problem?
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.
- DPF gun particulate filter cleaning fluid
Launch UK recently introduced its diesel particulate filter (DPF) gun to its range of diagnostic equipment. This is complemented by the DPF gun particulate filter cleaning fluid.
- 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.
- Under pressure
Even apparently simple problems require thorough investigation if you want to diagnose faults right the first time
- Diesel diagnostics for the workshop
I’m mindful of several recent diagnostic topics that focused on cutting edge opportunities such as noise and vibration analysis. It also reminded me of the most important aspects of fault finding; to focus on the symptoms, ask relevant questions and conduct a methodical approach based on systems knowledge, accurate data and a proven process.
All of this really boils down to training, experience, and confidence. There are no short cuts, cheap fixes or internet gurus. There are however basic steps that are easily introduced into your workshop procedures.
This brings me to the topic in hand. Can we conduct relativity simple tests on common rail diesel systems? Not only can we, but we must! Remember, the foundation rule of fault finding is a simple methodical approach. Don’t expect a magical fix-all in less than 1,000 words. However, I can provide a pathway that will illustrate the area of responsibility and potential investment in time and money.
Vital information
The first vital step is to listen and ask questions. Owners often have vital information. Remember this is not a recipe for short cuts or silver bullets for your machine gun. Your approach will always depend on the extent of problems. Will it run? are there any mechanical noises? Is there a loss of power? if so when? Is the fault intermittent and how did it start? There is an endless list of questions that will help establish a hidden history.
I often find that a physical examination or health check helps understand the way the vehicle has been driven and serviced. This will often expose basic problems especially with charge pressure circuits.
Try to explore all non-intrusive tests first. They may not be entirely logical in order of priority, but do provide results in the minimum time period. With experience, you will hone these steps into a razor-sharp intuitive process.
Serial investigation
Serial investigation is without doubt the correct first step. Do not jump to premature conclusions as serial data often shows symptoms, not cause. For example, a faulty air mass meter will cause EGR calculation error values, incorrect load and boost calculation. This is a common problem with many causes.
The volumetric efficiency relies on the intake system, swirl flap control, turbo spooling, and a free-flowing exhaust system. Please note that I keep my thoughts non-specific yet focused on all possible causes. This is a very important reaction in any diagnostic process.
Assuming a non-run condition, excluding any serial clues as often there are none, I would always check for the correct rail pressure. This can be done with a DMM. Expect around 1-1.5v with a quick rise time of 0.5-1sec. If it is slow to rise or low, check the priming system including the filter. This should be done with a gauge. Remember pressure, flow and pump current. This will depend on system type so check the schematics carefully. Most systems now prime at 5-6bar.
Isolate components
A slow rise time may be due to an internal leak or worn components within the high-pressure system. This includes the HP pump, rail limit valves, and injectors, as well as volume and pressure regulation devices. Always isolate various components and conduct a blind or proof test before suspecting the pump. They rarely fail, unless run dry or have contaminated fuel.
The PCM requires camshaft position data to sync the injectors and crank position once running. If recent belt replacement or engine repairs have been carried out, add this to your list. To check the injector sync against cam and crank position is a bit technical. To perform you will require a scope and current clamp.
Quite often the serial data identifies the incorrect timing sensor for position error. This is due to the PCM looking at the camshaft first. Slow rotation speed may be due to a faulty or incorrect battery, so check charge and health status with a suitable conductance tester. Yuasa have a fantastic free online training academy.
Next check relative compression. This is a simple cylinder balance check but when compared with current and rotation calculation will accurately predict correct compression.
Identify
A blocked exhaust or failed open EGR will prevent the correct combustion properties. Exhaust back pressure can easily be proven from the map and DPF pressure sensors. Plotting them with a scope will quickly identify intake or exhaust restrictions. The maximum DPF sensor value cranking or at idle should be 0.5-1.25 volts, 100mbar-1.5psi.
Injector type, solenoid or piezo faults will normally be identified within serial data. A single faulty injector circuit will normally shut down all fuel delivery. It is also worth noting that if a minimum rail pressure is not reached, the injectors will not be activated.
So back to priming. Leaks, faulty rail sensors will all contribute to a non-start.
If you are looking for more information, visit www.ads-global.co.uk for courses and dates, and Autoinform events.
