PeachParts Mercedes-Benz Forum - 96 E300 P0403 code

Quote:

Originally Posted by Stihlindixie (Post 3529443)

It's the EGR itself. All the electrics checked out.

There is a switch in the EGR valve with a cable (3 wires) from the valve to the EGR electronics. When applied vacuum makes the valve open, the switch sends a signal to the electronics, telling the system that the valve has operated. If that signal is not sent (or not received) a code is set.

The problem you are seeing could be due to not having vacuum to operate the valve, having vacuum but the EGR valve has a broken diaphragm so the valve won't work, or having vacuum and a good valve but the switch or wiring has failed so the signal doesn't get sent to the EGR electronics.

If the problem turns out to be in the EGR valve and not lack of vacuum or bad wiring, replacement of the EGR valve may be the only option. I don't kow if it's possible to replace a failed diaphragm in an EGR valve, as is sometimes possible in climate control vacuum pods.

Jeremy