ONE BOARD ECM USAGE/X CAR/2.5L DIAG. DIFF, 1 TO 2 BOARD ECM
On May 15, 1983, a new one-board ECM went into production for 1983 Phoenix models with the 2.5L engine and automatic transmission with 2.39 final drive ratio. The Phoenix will be the only model using the new one-board ECM in 1983. All other models will continue to use the two-board ECM until the start of production in 1984 at which time all models will use the one-board ECM.
ONE-BOARD ECM ONE-BOARD ECM (Controller) SERVICE PROM (Calibrator)
1226156 1226561
The one and two-board ECM's are not interchangable 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 Broadcast Code printed on the label. It is important that this information is carried over onto the new ECM.
2. The power steering pressure switch will not be used in the air conditioning clutch control circuit on one-board ECM equipped vehicles. Chart 9 in Section 6E2 of your General Carline Information (GCI) Manual must be used in diagnosis 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 in Section 6E2 of your GCI Manual must be used for diagnosing this system.
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.
