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Fault finding and a perfect fix

By autotech-nath on March 29, 2021

From finding the fault to the perfect fix – at a fraction of the price – By Barry Lawson, Ewan Lawson Motors.


As a member of Darren Darling’s DPF Doctor network, we follow the same process for every vehicle that comes through the door, no exceptions. Darren has established the DNA of the network. It starts with talking to our customer because gathering information about their perception of the problem, and how their vehicle has been performing, is crucial. This is also the time to put our customer at ease given so many have had bad experiences in the past with failed DPF repairs and large bills.

We then move to undertaking the assessment, looking at fault codes and live data. We carry out basic manual tests to ascertain the health of the DPF and pinpoint the faults that could necessitate repairs/further testing. So, back to the job in hand, on this occasion, a Ford Transit Custom.

The initial scan of fault codes came up with P2463 – DPF soot accumulation high and P25A1 – Exhaust Aftermarket glow plug circuit open. Gathering the data, it was clear why these codes had displayed. Live data showing that soot loadings were up 200% because the DPF hadn’t been regenerating, explained the fault code P2463.

The DPF is a self-cleaning filter so we must find the fault that’s stopping it from regenerating. As good as the JLM Lubricants’ DPF Cleaning Fluid is, it won’t stop the DPF from blocking again if the underlying faults are not correctly identified and fixed. Moving on a step, we undertook some basic testing. This is included in the £90 assessment fee, which we agreed at the outset with the customer.

We started by looking for the open circuit in the exhaust glow plug circuit, activating the circuit with the scan tool and loading it. We could see we had battery voltage at the glow plug, which shows good integrity in the wiring from the Engine Control Module to the multi-plug at the glow plug. But upon checking the resistance at the glow plug we could see it had failed – showing open circuit.

We had now identified the problem causing the DPF to fail at self-cleaning and regeneration.

We contacted our customer to explain our findings and provide the cost for repairs and cleaning. He had been told by another garage that other parts were to blame. So, the EGR had been replaced and the exhaust temperature sensors had been removed for cleaning. Alarmingly he had also been advised by this garage that the next step was to replace the ‘faulty’ DPF! The diagnostic computer or scan tool is often blamed because if that’s what the fault code says then the part must be changed. But the fault codes only provide a diagnostic direction. They should not be used to justify changing parts without undertaking further tests. Take this approach to its conclusion and you have a very unhappy customer parting with a large sum of money on repairs/replacements that were not needed. At all.

JLM DPF Cleaning Fluid

After explaining this to our (relieved) customer he was happy for us to carry on with the repairs and the cleaning of the DPF.

In the DPF Doctor network we use JLM Lubricants’ products from in-tank treatments, such as Regen Plus and Extreme Clean, depending on the status of the DPF. With the Ford Transit Custom, we used JLM DPF cleaning fluid – a two pack solution that is injected directly into the DPF, allowing it to soften up the carbon before flushing it through at low temperatures. This protects the DPF from the damage that a static regeneration may cause if it’s badly blocked.

With the JLM treatments applied, we took the van on a 50- mile extended road test so we could monitor live data. This showed the system was in full working order. The DPF pressure had dropped dramatically and was now back to nearly-new condition, well within the manufacturer’s specification.

This case study highlights that the DPF does not always need replacing. So, for a customer faced with this diagnosis from a mechanic, it’s wise to get a second opinion from a DPF specialist. For example, our customer had been quoted £1,300 from Ford for a new DPF. For £300, the DPF on their van had been restored to nearly new. A massive saving of £1,000, thanks to The DPF Doctor Network knowhow.

Being part of the DPF Doctor Network has really helped us grow in the field of diagnosing DPF faults. This in turn helps with diagnostic work in general. As a network, DPF Doctors talk regularly, especially online given the current restrictions. It is this shared experience, expertise and the regular training that helps drive the high standards of customer care and satisfaction that we’re renowned for. Long may this continue.

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