|Generation 4 EGR, DTC P0400 Failures, or bad idle.
1.8L 1996 to 1999 , and most newer 99 plus Vitaras and Trackers.
You have bad idle, (stalling) or are throwing Diagnostic Trouble code 400.
The is the first of the newer breed of simpler EGR systems.
It has one part.
A new Stepper motor driven valve.
All you can do is remove it and clean the valve , very carefully and the path through the intake for this EGR function.
Or replace it at great cost ! $$
The Coils can be measured left to right side, in top and bottom group. 20 ohms is typical reading.
A > B
C > B
F > E
D > E
There are other tests to do but one must use factory OBD2 test tools and is not DIY.
Leave unit plugged and and remove unit from Intake and then key on, and key off , many times and watch it.
It must move.
This moving can help the cleaning of the valve too.