SERVICE ENGINE SOON LIGHT COMES ON, NO CODE # STORED

MODELS: 1988 G2 VANS WITH 6.2L ENGINE (VIN CODEC )

Some instrument panel harness assemblies released for the 1988 G2 vans equipped with LH6 engines (6.2L diesel), have circuits #439 and #440 interchanged at the fuse block connector These circle cuits feed the 6.2L Electronic Control Module (ECM) ignition and battery inputs. With the circuits interchanged, the ECM will not store diagnostic codes.

This condition may be corrected by switching circit #439, Fuse Label "ECM B" (pink with black stripe) and circuit #440, Fuse Label "ECM I" (orange) at the fuse block connector as shown in Figures 1 and 2.

INSTRUCTIONS: (See Figures No. 1 and 2)

1. Disconnect the negative battery cable.

2. Remove the two dash panel connector block screws and remove the fuse block connector. The fuse block connector is located on the left side of the dash panel.

3. Remove the two screws in the fuse block connector and separate.

4. Using a small screwdriver, pry down on the lock tangs and remove terminal #439, Fuse Label "ECM B" and #440, Fuse Label "ECM I".

5. Interchange the terminals as indicated and reinstall by prying out the lock tangs and inserting the terminals into the connector.

6. Using the two screws previously removed, reconnect the fuse block connector.

7. Using the two screws previously removed, reattach the fuse block connector to the dash panel.

8. Reconnect the negative battery cable.

The instrument panel hamess assemblies should be reworked only if tbe vehicle comes into a dealership for ECM diagnostic related service work. This condition will not affect the vehicle's performance.

If the "Service Engine Soon" light comes on during vehicle operation the diagnostic trouble code will be erased the first time the key is tumed off. In order to obtain a diagnostic trouble code, (while wires are interchanged) leave tbe engine running.

All 1988 vehicles built prior to the VIN number listed below are affected:

GMC: 2GTEG25ClJ4512550

For repair to vehicles under warranty use:

Labor Op. Number: T7750 Labor Time: 0.3 hr

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.