ECM/PCM - Installation Procedures/Mem-Cal Concerns
91chevy25
GMC NUMBER: 91-6D-113
GROUP: 6D Engine Electrical
DATE: July, 1991
CORPORATE NUMBER: 176502R
SUBJECT: DAMAGE TO ECM/PCM CIRCUIT BOARD WHEN INSTALLING A MEM-CAL (NEW MEM-CAL INSTALL PROCEDURE)
MODELS: ALL 1986-91 TRUCKS WITH MEM-CAL
CONDITION: When installing a service replacement ECM/PCM, the use of incorrect MEM-CAL installation procedures may cause the ECM/PCM to fail before it can be installed in the vehicle. This condition may appear as if the ECM/PCM were defective when it was shipped to the dealership, when in fact it was damaged while being installed. In addition, this condition may also occur when installing an "updated" service MEM-CAL into the vehicle's original equipment ECM/PCM.
CAUSE: Excessive vertical force may be applied to the MEM-CAL resulting in flexing of the circuit board and damage to the connections between the circuit board and attached components. Excessive verticle force may be generated in two ways.
1. Incorrect MEM-CAL installation procedure.
2. Interference between MEM-CAL and cover.
CORRECTION: Use the following service procedure.
Service Procedure:
! Important
This procedure supersedes any instructions regarding MEM-CAL installation dated prior to September 1990.
1. Inspect the MEM-CAL to determine if a cork spacer is glued to the top side of the MEM-CAL assembly. If so, remove it prior to installation.
2. Align small notches with matching notches in the ECM/PCM MEM-CAL socket.
3. VERY GENTLY press down on the ends of the MEM-CAL until the locking levers are rotated toward the sides of the MEM-CAL. While continuing light pressure on the ends of MEM-CAL, use your index fingers to press the locking levers inward until they are snapped into place. Listen for click.
Notice: To avoid ECM/PCM damage, do not press on the ends of the MEM-CAL until the levers snap into place. Do not use any vertical force beyond the minimum required to engage the MEM-CAL into its socket.
4. Install MEM-CAL cover and install ECM/PCM in vehicle.