ECM/PROM - MIL ON/Poor Performance
Bulletin No. T 84-30
File In Group 6C
Number 70
Date Dec. '83
SUBJECT: ECM-PROM INCOMPATIBILITY - HT4100 ENGINE
MODELS AFFECTED: 1984 BROUGHAM, DEVILLE, ELDORADO AND SEVILLE
A "Service Now" tell-tale with unusable diagnostics and poor performance may occur on some 1984 HT4100-equipped vehicles after an ECM replacement. This is a result of an incompatibility of some 1984 PROM's with service ECM's. ECM service part number 1226028 is to be used on all 1983 and 1984 HT4100-equipped vehicles. Some ECM's were mislabeled as service P/N 1226463 rather than 1226028. This mislabeling does not affect the quality or operation of the ECM.
When diagnosis leads to replacing an ECM, the following procedure should be used to determine if an ECM-PROM incompatibility exists.
1. Transfer PROM from original ECM to service ECM.
2. If diagnostics are unusable, the PROM must be replaced. Refer to table below for proper service part number.
3. If a diagnostic code is present after an ECM replacement, the PROM should not be replaced and the Service Manual diagnostic procedures must be followed in the normal manner.
The following service PROM part numbers should be used to service all 1984 HT4100-equipped vehicles.
Broadcast Code Body Emission Replace With Broadcast Code
On OEM PROM Style Calibration Service P/N Service PROM
CAO E/K Federal Digital I.P. 16042066 DMX
CAS E/K & E Convertible Federal Digital I.P. 16042000 DLW
and Optional Axle
CAT E/K Federal Mechanical I.P. 16042069 DMY
CAX E/K & E Convertible Federal Mechanical I.P. 16042010 DLZ
and Optional Axle
CYP E Convertible Federal Mechanical I.P. 16042014 DMA
CYR E Convertible Federal Digital I.P. 16042017 DMB
CYS E Convertible Calif. Mechanical I.P. 16042020 DMC
CYT E Convertible Calif. Digital I.P. 16042024 DMD
DBB D Calif. 16042033 DMJ
DBC D Export 16042036 DMK
DBF E/K Calif. Mechanical I.P. 16042042 DMM
DBH E/K Calif. Digital I.P. 16042045 DMN
DBJ E/K Export Mechanical I.P. 16042048 DMP
DBK E/K Export Digital I.P. 16042051 DMR
DBL E/K Swiss Mechanical I.P. 16042054 DMS
DBM E/K Swiss Digital I.P. 16042057 DMT
DBN D Federal Optional Axle 16042060 DMU
DCM D Federal 16042063 DMW