P0400 causes
07-20-2017, 03:21 PM
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CLK55 AMG
P0400 causes
Does anyone know how the engine computer determines that something is wrong with the EGR valve and that it should throw a P0400 code? From looking on the web I have seen hints of two possibilities:
1. The computer commands the EGR valve to open and then looks for a change in voltage from the O2 sensors.
2. The computer commands the EGR valve to open and then looks for a change in intake manifold pressure.
I am getting a P0400 code. The EGR valve holds vacuum. The exhaust to intake port appears closed without voltage applied to the valve and opens when voltage is applied. The pipe that connects the EGR valve to the intake manifold is clean as a whistle. The vacuum hoses associated with the valve seem to be OK. My last guess is that the EGR valve is marginal or there is a problem with whatever the computer uses to decide to throw P0400. Is there anything else I can check before buying a new EGR valve?
Thanks.
1. The computer commands the EGR valve to open and then looks for a change in voltage from the O2 sensors.
2. The computer commands the EGR valve to open and then looks for a change in intake manifold pressure.
I am getting a P0400 code. The EGR valve holds vacuum. The exhaust to intake port appears closed without voltage applied to the valve and opens when voltage is applied. The pipe that connects the EGR valve to the intake manifold is clean as a whistle. The vacuum hoses associated with the valve seem to be OK. My last guess is that the EGR valve is marginal or there is a problem with whatever the computer uses to decide to throw P0400. Is there anything else I can check before buying a new EGR valve?
Thanks.
