ECM PROM, Replace

Fig. 165 Removing PROM carrier. 1984-86 models:

A PROM (Programmable Read Only Memory) is used in all ECM's except 1986-87 models equipped with 4-121 overhead valve engine and manual transmission. 1986-87 models equipped with 4-121 overhead valve engine and manual transmission have an ECM utilizing a MEM-CAL in place of the PROM.
1. Remove ECM from vehicle as described under ``Electronic Control Module, Replace.''
2. Remove PROM access cover. Note position of PROM in ECM. PROMs are not interchangeable. Replacement PROMs must be installed in some position and direction as defective PROM.
3. Grasp PROM carrier with the PROM removal tool, Fig. 165.
4. Gently rock the carrier from side to side while applying a firm upward force.
5. Remove PROM and carrier. Check part number of the new PROM to ensure it is the same as the defective PROM.
6. Position replacement PROM and carrier over PROM socket and press down firmly on top of carrier. Press down on carrier and ensure it seats squarely.
7. Replace PROM access cover, then install ECM on vehicle.
8. Start engine, enter diagnosis and check for code 51. If code 51 does not display, PROM is installed correctly. If code 51 is displayed, PROM is installed incorrectly and must repeat procedure. If PROM is installed backwards, it will be destroyed.