PROM ids

This table shows the PROM id associated with various Elans and the 13th digit of the PROM that should help to identify them.

Elan type	Prom id	Code	13th Vin digit	Comments
SE	9239 9929	ANXZ AUFH	1	The most common SE PROM. Can have problems meeting MOT emissions requirements due to the small adjustment range on the CO potentiometer. If your car has one of these and meets emissions requirements without difficulty you should stick with this chip. If, however, your Elan has trouble meeting emissions standards then look at the 9930 below...
SE	9930	?	1	As 9929 but with revised CO potentiometer calibration to ensure that emission standards can always be met within the adjustment range of the potentiometer. See here for details of the retrofit and here for how to find if your car has one. This chip will allow any emissions problems to be remedied but if the car is currently fitted with a 9239 or 9929 then the CO potentiometer will require require adjustment after the chip is fitted to prevent lumpy idle problems.
S2 and US - 49 States	1499	?	4 2	The only PROM used in the S2 and in US 49 states Elans. I've come across one in a Japanese Elan too. Catalyst equipped cars may not hit the Everest targets unless the backpressure from the catalyst equipped exhaust is addressed, although they should still gain appreciably in boost and power.
US Californian	9949	?	3	Strict emission PROM for Californian Elans. As above, catalyst equipped cars may not hit the Everest targets unless the backpressure from the catalyst equipped exhaust is addressed. Does not work in 49 States Elan.