Condition Not Present:

Sometimes the conditions can be duplicated by carefully warming the data line components with a heat gun and/or lightly tapping on them. If the condition cannot be duplicated on the vehicle during diagnosis, follow the procedure below:

1. Make sure that the grounds on the block near the starter solenoid, and on the fender near the battery, are clean and tight. Make certain there are star washers on the stud and that the studs are free of corrosion. Refer to Service Bulletin T-87-105, Group 8, for 1986-1987 Eldorados and Sevilles and T-90-55, Group 6E, for 1988-1990 Eldorados, Sevilles, DeVilles, and Fleetwoods.

2. On 1986 and 1987 Eldorados and Sevilles, make sure the engine-to-dash harness is not damaged and is secured to the brake booster. Refer to Service Bulletin T-86-35, Group 8.

3. Check the BCM EPROM and EEPROM and ECM CALPAK and PROM or MEM-CAL assembly for proper insertion into their respective sockets. Inspect components for bent or damaged legs.

4. Make sure both BCM and ECM have the correct PROM's for that model year.

5 . If the source of the intermittent problem has not been found and the intermittent condition
persists:

A. Verify good connections at the following components. Check each connection for proper latching and pins seated in the connector.

B. Replace the following components, one at a time, checking for reoccurrence of the intermittent condition after each component replacement. Follow the order listed. The order listed represents most likely to least likely cause of a multiple communications code condition:

^ BCM
^ ECM
^ BCM EPROM
^ ECM CALPAK or MEM-CAL
^ IPC
^ CCDIC
^ Programmer
^ Central Power Supply (CPS)
^ BCM EEPROM

For warranty purposes refer to the Labor Time Guide.