Fault code 3253 = DPF Inlet Temp sensor is Above its Normal Range.
this can happen if it is in a regen and it goes too high .... OR ... If it is not in a regen and the DPF inlet temp sensor reads higher than the normal exhaust temperatures.
* Could be one or more of ...
* Bad, mis-reading DPF inlet temp sensor or wiring for it.
* The engine is letting oil build up on the face of the DPF and igniting due to excessive blo-by or leaky exhaust turbine on turbo.
* You have a leaky Doser injector.
* Bad Valve guide seals that are quite bad, allowing oil into the exhaust.
* Leaky injector, allowing fuel to get into the exhaust via the exhaust stroke(s) of the engine.
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* Will it pass an injector leak test?
* Anyone pulled the Doser pipe away from the turbo, cranked the engine up, and looked to see if it is seeping fuel from its nozzle?
* Anyone pulled the intake and exhaust piping off the turbo to see if turbo is leaky?
* Anyone replaced the DPF inlet temp sensor to ensure it is not reading incorrectly?
* Does it have an aftermarket DOC or DPF unit on it? .. If so, this could be the issue.
* Anyone pulled the DOC and DPF, taken detailed pictures of their faces, and looked to see what kind of buildup is on the face of each?
* Anyone checked to see if the decomp tube does not have the dreaded "Volcano" in it, partially blocking off the exhaust system? ref:
http://rawze.com/forums/showthread.php?t...07#pid1807
* Any mysterious coolant losses?
* Anyone removed the turbo + exhaust manifold off after a 20-second quick cold-start, then shut down to see if any of the the exhaust valves (or inside of manifold) at one or more cylinders are wet with oil or fuel?
just some thoughts.