Repair Procedure

IMPORTANT WARNING: BEFORE INSTALLING THIS ECU (PN T0741580) ON ANY 1988 MODEL YEAR MEDALLION EQUIPPED WITH MANUAL TRANSMISSION, THE ECU WIRING MODIFICATIONS MUST FIRST BE PERFORMED. IN ADDITION, THE INSTRUCTIONS RELATING TO THE REMOVAL OF THE OXYGEN SENSOR MODULE MUST ALSO BE COMPLIED WITH FOR VEHICLES SO EQUIPPED.

FAILURE TO COMPLY WITH THESE IMPORTANT INSTRUCTIONS MAY RESULT IN SERIOUS MALFUNCTIONS IN ENGINE OPERATION UNDER CERTAIN CONDITIONS, INCLUDING CONTINUED ENGINE OPERATION AFTER TURNING THE IGNITION KEY TO THE "OFF" POSITION.

FIGURE 1:

ECU REMOVAL

The ECU is located in a plastic clamshell that is mounted under the black plastic cover (B) on the left inner strut tower in the engine compartment. See Fig. 1.

1. Disconnect the battery negative cable.

2. Remove the wing nut (A). See Fig. 1.

3. Remove the black plastic cover (B). See Fig. 1.

4. Pull back retaining clip.

5. Remove and open the plastic clamshell.

6. Disconnect the ECU connector.

7. Remove the ECU retaining nuts and remove the ECU from the clamshell.

FIGURE 2:

WIRING MODIFICATION

1. Locate the B+ latch relay (D) and the fuel pump relay (C), which are mounted on the inside of the upper half of the ECU housing. See Fig. 2.

The B+ latch relay has only small diameter wires attached to the connector. The fuel pump relay has two large diameter (10 gauge) wires attached to its connector.

2. Remove the connector from the B+ latch relay.

FIGURE 3:

3. Cut the yellow w/trace wire (E) approximately 1 1/2 inches back from B+ latch relay connector. Strip 1/2 inch of insulation from both ends of the cut wire. See Fig. 3.

4. Cut the small (20 gauge) brown wire (F) 1/2 inch from the B+ latch relay connector and carefully tape the connector end of the cut wire. Strip 1/2 inch of insulation from the harness end of the cut wire. See Fig. 3.

FIGURE 4:

5. Hold the harness end of the brown wire (F) parallel to the yellow w/trace wire (E), and slide 1-1/2 inches of heat shrink tubing (G) over the ends and down the wires about 2 inches to avoid damage during the soldering process. See Fig. 4.

6. Twist the end of the brown wire (F) and the two ends of the previously cut yellow w/trace wire (E) together tightly. See Fig. 4.

FIGURE 5:

7. Solder the twisted ends with resin core solder (Fig. 5). Carefully fold down the soldered joint onto the wires after the joint has cooled.

FIGURE 6:

8. Slide the heat shrink tubing over the soldered joint and shrink the tubing with a heat gun (H). See Fig. 6.

9. Reinstall the connector to the B+ latch relay.

FIGURE 7:

ECU INSTALLATION

1. Position the new ECU (PN T0741580) into the clamshell and install the retaining nuts.

2. Connect the ECU connector.

3. Place the top half of the clamshell on the bottom half and secure the assembly in position with the retaining clip.

4. Verify if the vehicle is equipped with the oxygen sensor module kit (Fig. 7).

FIGURE 8:

The module will be mounted on the right-hand headlight panel as shown in Fig. 8.

If the vehicle is equipped with the oxygen sensor module kit, the kit must be removed before completing the ECU installation. Refer to next section entitled, "Oxygen Sensor Model Kit Removal".

If the vehicle is not equipped with the oxygen sensor module kit, complete the following steps 5 and 6.

5. Position the black plastic cover and secure with wing nut.

6. Connect the battery negative cable.

FIGURE 9:

OXYGEN SENSOR MODULE KIT REMOVAL

1. Remove the oxygen sensor module (A) and ground wire eyelet (B) mounted on the right-hand headlight panel. See Fig. 9.

FIGURE 10:

2. Disconnect the wiring harness between oxygen sensor connectors (C) and (D). Set aside the two ends that are connected directly to the oxygen sensor module. See Fig. 10.

FIGURE 11:

3. Connect the two remaining ends and install in the retainer clip (H) on the engine block. See Fig. 11.

FIGURE 12:

4. Remove the plastic ties holding the voltage source wire (E) to the radiator upper cross member. See Fig. 12.

FIGURE 13:

5. Locate the green wire [mounted on the ECU clamshell (N)] leading to terminal "C" of the map sensor connector (M). See Fig. 13

6. Remove the heat shrink tubing that is covering a connection approximately 1-1/2 inches from the connector.

FIGURE 12:

7. Unsolder the voltage source wire (E) and remove from the green map sensor feed wires. Discard the oxygen sensor module kit. See Fig. 12.
8. Slide a length of heat shrink tubing over the green wire.
9. Resolder the two ends of the green wire together.
10. Slide the heat shrink tubing over the soldered connection, being sure that the tubing completely covers the soldered joint and any section of bare wires.

FIGURE 14:

11. Shrink the tubing with a heat gun (R). See Fig. 14.

12. Position the ECU black plastic cover and secure with wing nut.

13. Connect the battery negative cable.
POLICY: Reimbursable within the provision of the Warranty.


SRT/TIC INFORMATION:

OPERATION
OPERATION DESCRIPTION NUMBER TIME TIC

CO. ECU REPLACEMENT 0107 .7 1823