Mazda CX-5 DPF Blocked? Live Diagnosis and On-Car Fix (2.2 Skyactiv Diesel)

For business enquiries email [email protected] www.orileysautos.com When a Mazda CX-5 2.2 Skyactiv diesel turns up with the DPF light on, the engine light glowing, and reduced power, I already know the day is going to be busy. This one had all three, plus a very unhappy driver. In this post I walk through how I diagnosed the faults, checked the live data, cleaned the sensors and DPF on the car, and got the pressures back to a healthy level without removing the filter. Inside the car I had: * DPF malfunction warning * Engine malfunction warning * Noticeable reduced power On top of that the dash also warned of ice on the road because it was about minus two outside, so that part was nothing to worry about. I plugged in a Mukar 892 BT scan tool and pulled the codes. this tool is available from my affiliate link https://mythinkcar.com/?ref=dnnktcax Discount code JIMMYORILEY 1. Particulate filter regeneration duration 2. Soot accumulation 3. Ash accumulation 4. Blocked DPF 5. Turbocharger boost pressure not detected Regeneration duration told me the car had been trying to carry out DPF regens for too long, without the soot content dropping. That explains the soot and ash codes, because if the figures do not fall, the ECU assumes ash that cannot burn is building up. Next I watched live data for: * Turbocharger pressure * Exhaust pressure * Manifold (MAP) pressure * Engine speed The exhaust pressure trace was slow to fall, taking four to five seconds to drop back to normal after a rev. It should rise and fall almost in sync with engine speed. That delay told me the pressure pipe to the exhaust pressure sensor was restricted. The DPF differential pressure at idle was around 190 to 195 mbar, which is extremely high. For a car on about 50,000 miles, that is more like a blocked pipe or heavy soot than honest ash wear. Cleaning the Exhaust Pressure Sensor Pipe On top of the engine, Mazda puts the exhaust pressure sensor and its rubber hose and metal pipe. Access is actually quite kind. * Disconnected the hose and checked it with a small pressure gauge * Found it was not free flowing, the gauge moved instead of staying at zero To clear it, I used a drill with some doubled over guitar wire as a flexible cleaning tool, then added some DPF cleaning fluid down the pipe to soften the carbon. After working the wire through and running the engine, chunks of carbon spat out. Another quick test with the gauge showed no movement at all, which is what I wanted; a clear, free pipe. Sorting the MAP Sensor and Intake Side This sensor reads manifold absolute pressure, so it needs a clean passage if the ECU is going to see boost correctly. I carefully picked away the carbon so it could read again, taking care not to damage the sensitive element. The port in the manifold itself also needs to be clear, otherwise you get a delay on the readings. Ideally, these Skyactiv diesels really want the whole intake manifold and inlet ports walnut blasted about once a year. They are some of the worst engines I see for carbon build-up. Cleaning the DPF on the Car The DPF pressure sensor sits on top of the engine too, with two pipes running down to the filter. I identified the correct, larger diameter pipe by watching which one showed the high pressure. I then: * Fed a hose into that pipe * Introduced a mix of three different fluids, including Launch DPF cleaner * Let the fluid soak and reconnected everything The idea here was to break down soot and any softer ash inside the DPF without pulling it off the car. If the DPF were physically damaged or packed solid with hard ash, it would still need to come off, but at 50,000 miles I wanted to give cleaning a fair try first. I then started the engine and watched DPF differential pressure. After some fast idling and a short drive of about 1.5 to 2 km, the figures transformed. * Idle: about 4 mbar, which is right where I like to see it, between 4 and 6 mbar * Around 3,000 rpm: 46 to 49 mbar, very healthy Back on the graphs, the exhaust pressure sensor now showed sharp rises and drops that matched engine speed. The manifold pressure trace still had a slight delay, so a new MAP sensor might be needed later, but it was working well enough for now. Living with a Mazda Skyactiv Diesel With these Mazda 2.2 Skyactiv diesels, there is no permanent fix for soot problems. The design means you are likely to face this kind of cleaning work roughly once a year, especially if the car does lots of short trips. For now though, this CX-5 is breathing freely again, the DPF pressure is where it should be, and the owner can enjoy full power. If you run one of these engines, keeping an eye on DPF pressure and sensor health is the best way to avoid a big bill later.