These early Export CRDs like you and I have are very difficult to find a code reader that will work on them.
They use a PCI bus as apposed to the CAN/SCSI busses the later CRDS use.
I took my Export 2.5 CRD to the local Bosch Dealers to have my Bosch ECM read...they took one look at it and shook their heads.
However I use the "Key" trick often to pull out codes....with some limitations!
Without starting the engine rapidly turn the ignition ON/OFF 4 times.
After the 4th ON action leave the ignition ON.
The Odometer display will start displaying codes in sequence from the oldest...which may be ancient and no longer of interest...to the latest codes.
Write down the last few codes and post them up here.
The codes are not erased using this method.
Codes are stored only once so although you may be getting code P1234 all the time it will only show once.
The last two digits are sometimes transposed so a code of P1234 may actually show as P1243 which can confuse you if such a code does exist.
A lot of users here say "turn ignition ON/OFF 3 times".....this may be valid for newer USA models but I definitely know that 4 times works on my 2002 Export 2.5 CRD.
I sometimes deliberately cause a code...pull out one of the Glow Pug Relays and start the Jeep. This I use as a marker so that any brand new code I receive will show up last and I know that I have a new problem! You dis-connecting the MAP sensor will have caused a relevant code!
I have a neat download that specifically covers the early Export CRD error codes with information on what to do about them. I do not have the link for it but it is only 1 Mb in size so I can e-mail it to you if you PM me your e-mail address.