ERRATIC DIAGNOSTIC DISPLAY EXIT AND RE-ENTER

SOME 1983 CADILLACS EQUIPPED WITH DIGITAL FUEL INJECTION (DFI) MAY EXHIBIT AN IMPROPER ECC PANEL DISPLAY ONLY IN THE DIAGNOSTIC MODE. DURING THE DIAGNOSTIC ROUTINE, SUCH AS WHEN DISPLAYING TROUBLE CODES OR ENGINE DATA PARAMETERS, THE SYSTEM MAY UNEXPECTEDLY EXIT AND THEN RE-ENTER THE DIAGNOSTIC ROUTINE, BEGINNING WITH THE SEGMENT CHECK "-1.8.8." IF AN ENGINE DATA PARAMETER WAS BEING DISPLAYED, IT WILL BE NECESSARY TO AGAIN REQUEST THAT PARAMETER. THIS CONDITION AFFECTS ONLY THE ECC PANEL DISPLAY IN THE DIAGNOSTIC MODE. VEHICLE PERFORMANCE AND DRIVEABILITY ARE UNAFFECTED AND DISPLAYS ARE UNAFFECTED WHEN NOT IN THE DIAGNOSTIC MODE. DO NOT REPLACE THE ECM UNLESS THE FREQUENCY OF OCCURRENCE IN THE DIAGNOSTIC MODE IS SO GREAT AS TO PREVENT EFFECTIVE DIAGNOSIS OF THE VEHICLE USING THE ON-CAR DIAGNOSTICS. THE FOLLOWING RANGES OF VEHICLES MAY BE AFFECTED BY THIS CONDITION: CAR LINE AND EMISSION SYSTEM C FEDERAL B.C. NO. RANGE 206500- 212768 CAR LINE AND EMISSION SYSTEM C ALTITUDE B.C. NO. RANGE 206500- 212768 CAR LINE AND EMISSION SYSTEM C CALIFORNIA B.C. NO. RANGE 206500- 211443 CAR LINE AND EMISSION SYSTEM E FEDERAL B.C. NO. RANGE 637400-? CAR LINE AND EMISSION SYSTEM E ALTITUDE B.C. NO. RANGE 637400-? CAR LINE AND EMISSION SYSTEM K FEDERAL B.C. NO. RANGE 817200-? CAR LINE AND EMISSION SYSTEM K ALTITUDE B.C. NO. RANGE 817200-? VEHICLES PRIOR TO THIS B.C. NO. RANGE MAY ALSO EXHIBIT THIS DIAGNOSTIC EXIT AND RE-ENTRY CONDITION, BUT ON A VERY INFREQUENT BASIS, AND ONLY WHEN IN THE DIAGNOSTIC MODE. DIAGNOSTICS WILL BE USABLE AND THE ECM SHOULD NOT BE REPLACED FOR THIS CONDITION ON VEHICLES BEFORE THE AFFECTED RANGE. IF NECESSARY, A JUMPER BETWEEN PINS A AND B OF THE ALDL CONNECTOR WILL PREVENT A POSSIBLE DIAGNOSTIC EXIT AND RE-ENTRY ON VEHICLES BEFORE THE B.C. NO. RANGE LISTED ABOVE. THIS JUMPER WILL NOT EFFECTIVELY PREVENT THIS CONDITION ON VEHICLES WITHIN THE AFFECTED B.C. NO. RANGES. ELDORADOS AND SEVILLES WITH CALIFORNIA EMISSION SYSTEMS (NB2), AND ALL GMWDD SERVICE STOCK ARE UNAFFECTED BY THIS CONDITION. VEHICLES AFTER THE ABOVE B.C. NO. RANGE ARE ALSO UNAFFECTED, PROVIDED THE ECM HAD NOT BEEN PREVIOUSLY TRANSFERRED FROM ANOTHER CAR. ECM'S CAN BE IDENTIFIED AS FOLLOWS: 1.EARLY ECM'S - DIAGNOSTIC EXIT AND RE-ENTRY OCCURS VERY INFREQUENTLY. THESE ARE IDENTIFIED BY THE MANUFACTURING CODE (FIRST FIVE DIGITS) IN THE 15-DIGIT ECM SIDE RAIL NUMBER CONTAINING ONE OF THE FOLLOWING NUMBER COMBINATIONS (SEE FIGURE 1): 60903 60904 60906 2.ECM'S SUSCEPTIBLE TO DIAGNOSTIC EXIT AND RE-ENTRY. THESE ARE IDENTIFIED BY THE PRESENCE OF ALL OF THE FOLLOWING: A.THE MANUFACTURING CODE (FIRST FIVE DIGITS) IN THE 15-DIGIT ECM SIDE RAIL NUMBER IS 60907 (SEE FIGURE 1), AND B.THE LETTER "C" DOES NOT APPEAR BELOW THE DE-GM LOGO IN THE PART NUMBER LABEL (SEE FIGURE 2) OR ABOVE THE SERVICE PART NUMBER (SEE FIGURE 3). 3.LATE ECM'S - NOT SUSCEPTIBLE TO DIAGNOSTIC EXIT. THESE ARE IDENTIFIED BY ANY ONE OF THE FOLLOWING: A.A MANUFACTURING CODE (FIRST FIVE DIGITS) IN THE 15-DIGIT ECM SIDE RAIL NUMBER IS 60907 (SEE FIGURE 1) AND A LETTER "C" OR HIGHER APPEARS EITHER BELOW THE DE-GM LOGO OR ABOVE THE SERVICE PART NUMBER, INDICATING A REWORKED UNIT (SEE FIGURES 2 AND 3), OR B.A DATE CODE (LAST FOUR DIGITS) IN THE 15-DIGIT ECM SIDE RAIL NUMBER OF 3076 OR HIGHER (SEE FIGURE 1). IF AN ECM IS REPLACED WHEN DIAGNOSING A VEHICLE CONDITION BECAUSE DIAGNOSTICS ARE NOT USABLE, THE NORMAL DIAGNOSIS MUST THEN BE PERFORMED SO AS NOT TO OVERLOOK THE CAUSE OF THE ORIGINAL CONDITION CAUSING OWNER COMMENT. DO NOT ASSUME THAT ECM REPLACEMENT WILL CORRECT THE VEHICLE CONDITION WHICH CAUSED THE OWNER COMMENT. THIS IS UNLIKELY SINCE THE DIAGNOSTIC EXIT AND RE-ENTRY CONDITION IS NOT NOTICEABLE BY THE DRIVER AND DOES NOT AFFECT VEHICLE PERFORMANCE OR FUNCTION (OTHER THAN DIAGNOSTICS). WHEN REPLACING AN ECM, ANY STORED TROUBLE CODES ARE CLEARED WHEN BATTERY POWER IS REMOVED FROM THE ECM. THEREFORE, IT IS NECESSARY TO ROAD TEST THE CAR AFTER AN ECM REPLACEMENT IN ORDER TO RESET ANY TROUBLE CODES THAT MIGHT HAVE BEEN PRESENT BEFORE THE ECM WAS REPLACED.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.