AUTO. DOOR LOCKS ACTIVATED TO LOCK WHEN IGN. IS TURNED OFF

SUBJECT: AUTOMATIC DOOR LOCKS (AU4) ACTIVATED TO LOCK POSITION WHEN IGNITION IS TURNED OFF (NEW-PARTS)

VEHICLES AFFECTED: 1985-89 C

CONDITION:

--------- The above condition can occur on any 1985 thru 1989 'C' models. It is most likely to occur on vehicles with Nippondenso fuel pumps.

The fuel pump armature spins after the ignition is turned off. The armature then acts as a generator that can transmit a transient electrical pulse into the automatic door lock (ADL) circuit causing the doors to lock.

DEALER ACTION

To prevent the electrical pulse from entering the ADL circuit, a zener diode can be added. The diode blocks the pulse.

NOTICE: Be certain to install the zener diode in the proper direction. Follow the instructions carefully. Improper installation will not correct the condition.

1. Disconnect battery negative cable.

2. Open glove box (1) fully (pull rubber retainers (2).

3. Disconnect ADL controller (3) from connector bracket (see Figure 1).

4. Cut and strip pink/black wire (connector terminal "C") (see Figure 2).

5. Slip heat shrink tubing over wire.

6. Use wire splice clips to install diode. Install diode as shown in Figure 2 with silver band end towards fuse 16. Use care to ensure the diode is installed properly).

7. Fold wires and diode as shown in Figure 2.

8. Slide heat shrink tubing over diode and shrink. Figure 3 shows the revised schematic.

9. Connect ADL controller to connector bracket.

10. Reinstall glove box door part retainers.

11. Reconnect battery negative cable.

12. Reprogram all electronic systems, set clock, etc.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.