For 1990-2009 cars

# 1981 LIMOUSINES DFI INSTALLATION OF JUMPER HARNESS

1981 Limousines are equipped with the Digital Fuel Injected (DFI) V8-6-4 engine. These vehicles are not equipped with a MPG display panel; therefore, you cannot pass some of the 70 series switch tests, enter the output cycling and cylinder select tests, or observe engine parameters in the normal fashion using the instant/ average, MPG reset, and active cylinder buttons on the MPG display panel. These diagnostic features can be accessed by use of a jumper harness which can be obtained from your local zone office or constructed as shown on revers side.* The connectors are available from GMWDD in quantities of ten. Although it is not necessary to use brown and brown/white wire, contrasting colored wire should be used to facilitate testing. When installed, this harness should be left in the vehicle for future use.

*Limousines built after approximately May 1, 1981 should have the jumper harness installed.

Follow the procedure below to activate parametric and cylinder selection diagnostics:

1. Determine if a jumper harness is installed on the vehicle. If so, proceed immediately to step 5.

2. Remove P-3 (orange) connector from ECM.

3. Remove lock tab and install jumper harness brown wire into vacant connector cavity #7. Install brown/white or white harness wire into vacant connector cavity #3. Reinstall lock tab. (If not using a harness provided by the zone, your wire colors may be different. Make note of the color wire in each terminal to facilitate diagnostics.)

4. Reinstall P-3 (orange) connector to ECM.

5. Using the jumper harness connector and a jumper lead, the following diagnostic functions can be performed:

To advance from 70 to 95: Ground brown wire (pin 7) momentarily

To pass switch test 78: Ground brown wire (pin 7) momentarily

To pass switch test 79: Ground brown/white wire (pin 3) momentarily

To hold 8 cylinder operation: Ground brown wire (pin 7)

To hold 6 cylinder operation: Ground brown/white wire (pin 3)

To hold 4 cylinder operation: Ground both wires (pin 7 & 3) at the same time

To increment parameters: Ground brown wire (pin 7) momentarily

To decrement parameters: Ground brown/white wire (pin 3) momentarily

For warranty purposes, use Operation No. T6043, Limousine Jumper Harness Install, at .3 hour.

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.