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Technical Information

Technical Information

1. Subaru Recall information. Copy & Paste in your browser to see if your vehicle is affected.

2. Diesel Warning lights - Explanation

We have a lot of customers who experience Diesel warning lights coming on at one time or another. Understanding what the lights are telling you can reduce the stress of the whole situation. Here is a basic outline. I hope it helps.

Most of the time error lights relating to Subaru Diesel's are either due to Soot Accumulation, the build-up of soot in the front exhaust section/trap (DPF- Diesel Particulate Filter) or due to Engine oil Dilution due to the intervention of the engine's computer trying to lower the soot level in the DPF. 

The engine's computer constantly measures the pressure in the DPF to ensure that the exhaust system does not become restricted causing a reduction in engine performance

You may wonder why one would use a DPF? To improve engine output & fuel economy of a Diesel engine, the fuel injection pressure is increased to almost 200,000psi @ this extreme pressure economy and output is achieved.

With every great idea there are trade-offs. Due to the very high fuel pressure, small diesel particles may pass through the combustion process attaching themselves to soot without being burnt, this, in turn, becomes a health hazard leading to irreversible effects hence a DPF is introduced.

When the soot level exceeds 85% the vehicle speed request light illuminates. It is recommended that the driver drives over 60kph or more for 15 mins. It the soot accumulation reduces to approximately 56% the light will extinguish.

Note:  If the soot accumulation continues to climb to and above 100% then the DPF warning light will start to flash indicating a fault. Extended driving in this condition will cause a reduction in engine output and may damage the DPF.


As Diesel engines are very efficient, they do not generate a lot of exhaust temperature. When the required exhaust temperature to thermally clear soot levels cannot be reached, the engine's computer will intervene by altering the engines mixtures to try and raise the exhaust temperature to lower soot levels. The problem here is that the more intervention needed by the vehicles computer, the more fuel is injected causing fuel to enter into the vehicles engine oil system degrading the oil. High levels of oil dilution will affect the wear rate of engine components, reducing engine life; hence why engine oil dilution is calculated.

Note:  If oil dilution reaches 10% - 15% varying based on the model variant the DPF warning light flashes and DTC P1468 is stored in the engine's computer with no engine light illuminating.

The engine oil must be replaced with the calculated values reset.

The question that you may be asking? How would one know the difference between soot accumulation and oil dilution light, when they are both using the same light.

Soot accumulation will always become a solid warning light when the soot level has reached 85% if the level does not reduce, only then will the light start to flash.

Where with Oil dilution, if the dilution reaches 10-15% dependant on the model variant, the light will go straight to a flashing state.

Another tip.  If the DPF condition is fine and it's not soot that has triggered the light, when one turns the ignition to the on state (engine off) if the DPF warning light is on for 2 seconds then extinguishes but you have a flashing DPF only after start up, this would indicate that the oil dilution is high and the oil needs to be changed with the oil dilution calculations in the engine computer reset.

3. 2.5L SOHC Head Torque Specification & Procedure

1. Ensure to clean all Bolt threads and lubricate well with engine oil or thread lube. (Tip) Laying bolt threads against each other will indicate whether the threads are stretched and the bolts need to be replaced) With this guide, the threads should mesh with each other nicely.

Replacement bolts can be found in store.

2. Tighten all bolts to 29nm or 22ft-lb (starting with the 2 centre bolts then continuing to the outer bolts at 10 o'clock or 5 o'clock) then complete the procedure for the opposite bolts until all are torqued. 

3. Further, tighten all bolts in the same procedure as above to 69nm or 51ft-lb

4. Loosen all of the bolts by 180 degrees in the reverse order of installation.

5. Further lossen all of the bolts by another 180 degrees in the reverse order of installation.

Note: This procedure is important to pre-crush the headgasket to prevent external leakage. 

(Revised Headgaskets for most models can be found in store)

6. Tighten all bolts to 42nm or 31ft-lb in the sequence explained above

7. Tighten all bolts by 80 - 90 degrees in the sequence explained above.

8. Tighten all bolts by 40 - 45 degrees in the sequence explained above

9. Further, tighten the 2 centre bolts by 40 - 45 degrees making sure the total angle does not exceed 90 degrees.







Subaru Service FAQ

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