C 2500 Truck 2WD V6-262 4.3L VIN Z (1992)
1992 LB4 VIN Z with "cold knock" only
1992-93 LB4 VIN Z with "cold knock" and installed field fix PROM OR with "cold knock" and detonation
1990-95 LB4 VIN Z
Install check valve oil filter P/N 12555891 (FRAM PH3980). If the filter does not cure the condition, install the appropriate calibration from the tables
(calibrations are available for all 1992 and some 1993 LB4 applications). If a calibration is not offered or does not cure the short duration cold knock
