2006 LS Engine light P0400

[xr8 007]

I have a 2006 LS Focus. I keep getting the engine light come on, as per the OBDII scanner spits out code P0400 (exhaust gas flow something). Did the obvious google search and seemed that most people changed the EGR valve and Intake manifold control valve purge solenoid.

The only symptoms the car demonstrates is that it runs abit rough on idle when its warmed up and sitting in traffic however I more inclined to blame the engine and trans mounts for this as the idles are ok however the car vibrates abit.

So I changed both however the engine light keeps popping back up. Any ideas on anything else I can be changing or looking at? Thanks heaps in advance.

[DZFord]

Consider blocked / clogged up EGR passages. There is an EGR tube under the intake manifold, as well as the passages in the cylinder head.

The EGR flow is monitored by the MAP sensor (or TMAP sensor in this case as it has the intake air temp sensor incorporated). Your MAP sensor readings seem all OK?

Of course, there could be an ECU error in controlling the EGR / wiring fault, but this is difficult to check without an oscilloscope, as the EGR stepper motor is apparently pulse with modulated.

[xr8 007]

Thanks heaps for the reply DZ.

Silly question but you asekd if my MAP sesnor read ok? Is there a way of checking?

[DZFord]

Not a silly question - just use your scan tool to graph manifold pressure against engine load/RPM. Ensure it increases / decreases as expected - eg. increase in manifold pressure with increase in load.