Cadillac Repair Questions? Ask a Mechanic for Answers ASAP
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In some cases this fault here may be caused by a lack of fuel through the fuel injectors or to much fuel through one or more injector intermittently.I have seen fuel injectors act up like this before intermittently with the affected injectors sometimes needing replaced.If you have not tried having the injectors cleaned I would see if this corrects the fault.You can also try and add injector cleaner to the fuel tank at around 1/4 tank and run to near empty to see if this clears up the injectors.
In some cases a restricted fuel filter or fuel pump that is acting up intermittently will also cause this type of fault here.If you have not had the fuel system tested I would see if it is at fault needing replaced to correct this issue as well.
All of these need checked into/tested to locate and repair the fault.
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Fuel pressure key on and engine off should be between 41 and 47 psi.Running you might see the lower end 36 to 41 psi so it looks o.k. right now but I would re check this when the vehicle is acting up as the pump may be providing pressure now but when the vehicle is acting up it may be lower which can indicate a fuel pump issue here.You may have some injectors that are gummed up.I would drive the vehicle with the cleaner in the tank to near empty and see if it clears up then at all.
U1000 will set when a loss of communication with one or more computers in the vehicle occurs.This won't cause the misfire and diagnostics say to diagnose and repair any other faults and codes first then see if this code returns again.
The fuel pressure will hold steady for the most part with the regulator disconnected and this is normal.
Since the fault has not re occurred here the issue may have been resolved.I would clear out the codes and continue to operate it to see if it acts up again at all.
O.k.,the code P0420 indicates a fault with low exhaust flow.Usually this is the catalytic converter that becomes restricted and usually due to a misfire with excess fuel that can build up in the catalytic converter.This may be the case here with yours needing replaced.It can also indicate that the rear oxygen sensor is faulty but in most cases it is the catalytic converter that needs replaced and is most likely the result from the misfiring that was occuring.