ONE BOARD ECM USAGE/X CAR/2.5L DIAG. DIFF, 1 TO 2 BOARD ECM

MODELS AFFECTED: 1983 1/2 SKYLARK MODELS EQUIPPED WITH 2.5L EFI ENGINE AND AUTOMATIC TRANSMISSION (2.39 FINAL DRIVE RATIO)

NOTICE: This bulletin supersedes Bulletin 83-152, File Group 64A, #18, to correct the word now underlined in Step 3. Please discard original and replace it with this one.

On May 2, 1983, a new one board ECM went into production for 1983 Skylark models with the 2.5L engine and automatic transmissions with 2.39 final ratio.

ONE BOARD ECM (Controller) ECM (Calibrator-PROM)

Service #1226156 Service #1226561

The one and two board ECM's are NOT interchangeable and will be noted as either a "one-board" or "two board" ECM in the parts catalog. Additional service concerns are as follows:

1. Initially, one board replacement ECM's will not have the production (OEM) part number or the PROM broacast code printed on the label. It is important that this inforamtion is carried over onto the new ECM.

2. The power steering pressyre switcg will not be used in the air conditioning clutch control circuit on one board ECM equipped vehicles. Diagnosis Chart 9 (Figure 1 and 2) must be used for these vehicles.

3. The power steering pressure switch will now be used as a completely separate input to the ECM. This input will be used to anticipate high power steering loads in order to maintain a constant engine speed. Chart 11B (Figure 3) must be used for diagnosis of this system.

NOTICE: Part Number 1226561, PROM, will be available from WDDGM after July 18, 1983.

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.