basically 4 weeks ago my 07 focus 100,000mls diesel had 'engine systems fault' warning and when in to limp mode, took it the garage and he said it was dpf and recommended trying a chemical flush, which solved the problem..... until few days ago same thing happened, back to garage. he ran another diagnostic(for free)(uploaded the report) and he said the same dpf code again but he tested the pressure going though it 0.28 and its clean. so its either giving him the car for a few days where he will charge me hourly rate to find the issue or change the dpf and hope it works. i think i can change the DPF if that required or pressure was the old one and see if that works but i thought id get your opinion first,

 

all reply's greatly appreciated 

in addition when he tried to clear the fault codes the only one he couldn't delete was P242F, all other code he could delete

DTC P242F = Diesel Particulate Filter Restriction Ash Accumulation

The Powertrain Control Module (PCM) monitors the pressure decrease at the DPF. If the pressure decrease exceeds the maximum allowed value the PCM activates the regeneration proces. During a regeneration the PCM expects the pressure to decrease. The amount of pressure decrease expected by the PCM is based on the temperature and flow of the exhaust gas. The test fails when the pressure reading at the diesel particulate filter pressure sensor does not decrease by the amount determined by the PCM. When this test fails the DTC P242F is generated.

This problem can have several causes:

1. Blocked/clogged DPF.
2. Defective differential pressure sensor.
3. Defective differential pressure sensor hoses.
3. Defective exhaust gas temperature sensor.

 

Personally I would inspect the differential pressure sensor and hoses and exhaust gas temperature sensor first. If these are in good working order the problem must be the DPF.