Unfortunately, these locomotives suffered from two distinct problems: 
During the late 1950s and early 1960s, following the publication of the Andrews Report, CIÉ followed a path of large-scale closures of branch lines, leaving them without a purpose.

The locomotives were of insufficient power for their duties and their Crossley engines suffered reliability problems.

Replacement engines:
Because of the problems with the Crossley engines attempts were made to fit the locomotives with more suitable equipment.
Between 1965 and 1980, Maybach MD650 engines of 980 horsepower (730 kW) were fitted in Nos.
233 and 234.
From 1969, however, a permanent solution was found by fitting the entire class with General Motors engines, a similar process that was also undergone by the 001 Class).

 New Duties:
From 1969 the class were given new duties, being partnered with former 2600 class diesel multiple units converted to four-car push-pull carriage rakes to operate the suburban services around Dublin.
In 1984 the Dublin suburban lines over which they worked were electrified and new electric multiple units operated the renamed Dublin Area Rapid Transit (DART) system.

The first member of the class to be withdrawn was No.
B201, being bomb damaged in 1973.
 The remaining members of the class, except those sold to NIR, were withdrawn over the two years following the opening of the DART system having completed 30 years service for their operators.
Unfortunately, these locomotives suffered from two distinct problems: 
During the late 1950s and early 1960s, following the publication of the Andrews Report, CIÉ followed a path of large-scale closures of branch lines, leaving them without a purpose.
The locomotives were of insufficient power for their duties and their Crossley engines suffered reliability problems.
Replacement engines:
Because of the problems with the Crossley engines attempts were made to fit the locomotives with more suitable equipment. Between 1965 and 1980, Maybach MD650 engines of 980 horsepower (730 kW) were fitted in Nos. 233 and 234. From 1969, however, a permanent solution was found by fitting the entire class with General Motors engines, a similar process that was also undergone by the 001 Class). 
 New Duties:
From 1969 the class were given new duties, being partnered with former 2600 class diesel multiple units converted to four-car push-pull carriage rakes to operate the suburban services around Dublin. In 1984 the Dublin suburban lines over which they worked were electrified and new electric multiple units operated the renamed Dublin Area Rapid Transit (DART) system.
The first member of the class to be withdrawn was No. B201, being bomb damaged in 1973.  The remaining members of the class, except those sold to NIR, were withdrawn over the two years following the opening of the DART system having completed 30 years service for their operators.
CIE 201 Class