Brakes - (4WAL) Lamp ON/False Codes Set
90Chevy33Number: 91-72-5
Section: 5
Date: September 1990
Corp. Bulletin No.: 065017
Subject: FALSE CODES 41, 42, 43, 44, 46, 48, 51, 52, 53 AND 54
Model and Year: 1990-91 M/L AND 1991 4-DOOR S/T UTILITY VEHICLES WITH 4WAL
TO: ALL CHEVROLET DEALERS
Some 1990-91 M/L vans and 1991 4 door S/T utility vehicles may experience a condition in which the ANTI-LOCK light is illuminated and the anti-lock feature of the brake system is deactivated without a true malfunction of the 4WAL module.
The condition may cause one or any combination of the following trouble codes to be falsely set and stored in the Electro Hydraulic Control Unit (EHCU) memory.
Figure 1 - S/T Truck:
Figure 2 - M/L Van:
The root cause of this condition is a poor connection at the vehicle junction block located against the vehicle cowl on the left side of the vehicle (see Figures 1 and 2).
If a vehicle exhibits the above codes, technicians should inspect the junction block connector for looseness and corrosion or contaminants. Any of these will cause a poor connection.
Once the connector has been cleaned, check all male to female connections to assure that all female sockets hold the male inserts securely.
When the Junction block is secure, clear the codes from the EHCU and run a function test using Tech 1 to verify the repair.