ECM - Revised Replacement Procedure

Number 87-6(Gasoline)-40 Date 5/87
Subject: REVISED ECM REPLACEMENT PROCEDURE - CHART C-1


1982-87 ECM EQUIPPED VEHICLES
The purpose of this bulletin is to introduce new ECM test procedures to reduce the possibility of multiple ECM failures on any one vehicle..

Since 1982, most ECM's have used an integrated circuit (IC) in place of separate transistors to turn "ON" or "OFF" different components controlled by the ECM. These IC's are called quad drivers (QDR). Each QDR has four separate outputs, meaning it can turn "ON" or "OFF" four different items independently.

A failed QDR usually results in an ECM output becoming either shorted to ground or open. Many times all four QDR outputs will be inoperative if just one vehicle circuit is faulty.

The revised diagnostic incorporates new test procedures designed to identify a damaged QDR. Once identified, the circuit must be repaired to reduce the incidence of repeat ECM failures.

This chart replaces the current service manual procedure for either:

ECM - DIAGNOSIS CHART:

1. Chart C-1 ECM replacement check, or

2. Any diagnostic chart where "Replace ECM" is the conclusion, especially if a footnote indicates checking certain circuits for less than 20 OHM's resistance.

It is strongly suggested that this chart be used whenever an ECM replacement is indicated for 1982-87 vehicles.



QDR Application Chart For CHART C-1

The following chart contains ECM QDR arrangement for all ECM models thru 1987.:

QDR Application Chart For CHART C-1