Toyota d4d i have 1238 codes

What country>?' what year, car? we can not guess that.
diesel.
the car , all cars have a book, and this book is called the FSM
for factory service manual. toyota made it and sells it.
the book has a section called diagnstic codes, DTC errors
it shows all codes , the tests it does, how it works and then tells
the mechanic what to do (more tests) to isolate true cause.
all cars made , same. answer. its in that book.
some countries use different diesel systems (EFI) like here in USA
totally differ and regulatoed by EPA law.
what your countries laws do , ive not a clue but matters big time
what country, is this direct injection>??????


is that really P1238
did you scan the PCM yet,? with a real scan tool
there can be 5 more DTC error there, all VALID .

now i google for you, yes, wild crazy idea. can land on wrong dtc
http://www.moranbahweather.com/toyota/hilux/repair2/html/frame_rm000001ar3008x.html

but with no county,
go to toy in your county and get the book, and win.
every time.