EXPERTEC TSB (T90-90)

Publication date: 1990-08-08
Reference number: T90-90
Supersedes refnos: T89-13

EXPERTEC TSB

TECHNICAL SERVICE BULLETIN

Reference Number(s): T90-90, Date of Issue: 08/08/90
Superceded Bulletin(s): T89-13

INTERMITTENT CODES E047, B333 - B334, B335, B336 AND/OR B337

Model(s): 1986-90 Cadillac Eldorados and Sevilles; 1987-90 Cadillac Allantes

Bulletin No.: Cadillac T90-90

Date: 08/08/1990

NOTE: This bulletin supersedes T89-13 which should be discarded.

BULLETIN ILLUSTRATION LIST

Fig 1: Graphic

Fig 2: Graphic

Fig 3: Graphic

Fig 4: Graphic

SERVICE INFORMATION

This bulletin supersedes T-89-13 which should be discarded. This bulletin is being updated to include additional model years and to update the diagnosis information. Some 1986-1990 Eldorados, Sevilles and 1987-1990 Allantes may experience intermittent setting of data line codes E047, B333, B334, B335, B336 and/or B337. These may all be set at one time or in any combination.

Single codes should be diagnosed using the appropriate trouble tree in the Service Information Manual. In addition to the codes, some of the following may also occur:

IPC and/or the CCDIC flashes on and off or bright/dim
Fuel gage flashes "E"
Trip odometer resets to 0
ECC switches to full heat at high blower speed out the front defrost ducts
Erroneous displays appear on the CCDIC
ECC panel will not respond to pressing of buttons
CCDIC may display SYSTEM PROBLEM

These conditions may be caused by either a damaged data line circuit or one of the components connected to the data line. When operating normally, the serial data line voltage should continually fluctuate from 0 to 5 volts.

DIAGNOSIS

If the serial data line has been shorted to ground, the voltage at the Assembly Line Data Link (ALDL) will be 0V. If it has been shorted to voltage, it will be over 5 V. If one of the components on the serial data line is affecting the data line voltage, the serial data voltage at the ALDL connector will be a steady value anywhere between .1 and 5 volts (e.g., 2.7V, 4.8V etc.). It has been found that a steady serial data line voltage of 4.7 to 4.9 volts usually means the BCM is the cause, and .1 to .3 volts usually means the ECM is the cause.

CONDITION PRESENT

This section explains how to find the cause of a data line condition that is present all the time or can be duplicated for diagnosis. Using the instructions in this section, perform the appropriate "condition present diagnosis" trouble tree.

The condition present diagnosis charts have many branches that instruct to check for voltage/ground on the 800 circuit. First, check for voltage at the specified pin with the ignition on (there should be less than . 1 volts). If there is no voltage, check the circuit for resistance to ground (should read open to ground on the highest resistance setting). The trouble trees are written so that whenever these checks are made the right components are connected/disconnected to prevent false readings. Therefore, do not reconnect components until instructed to do so or when diagnosis is completed.

If the voltage/resistance test indicates there is a problem in part of the 800 circuit, check that section of the 800 circuit by tracing the wire and checking connections in that segment. Refer to page 8A-50-0 in the Service Information Manual for circuit layout. If the circuit is difficult to trace or no problem in the circuit is visible, it may be better to restring the segment involved. If this segment includes the flex circuits behind the IPC on E/K models, isolate the problem to the wiring up to C201 or a C201/flex circuit problem. If the problem is in connector C201 or the flex circuits, the entire carrier must be replaced.

NOTE: Data line conditions tend to be intermittent and may disappear while disconnecting/reconnecting components. Therefore, double check each step of the trouble tree to make sure the conditions have not disappeared during testing. If they have disappeared, return to the last step taken while the condition was present and continue when condition returns. If the condition cannot be duplicated again or the condition present diagnosis does not lead to the fix, perform the condition not present diagnosis.

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:

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

WARRANTY INFORMATION

For warranty purposes refer to the Labor Time Guide.