MANUAL UPDATE-ADD CODE 32 DRIVEABILITY AND EMISSIONS

Models Affected: 1989 GRAND AM

This bulletin is to add Code 32 Chart to Section 6E2, "Driveability And Emissions" of the 1989 2.5L (VIN U) Grand Am Carline Service Manual. Please refer to this bulletin when diagnosing Code 32 on these vehicles. Included with this bulletin is the Code 32 Diagnostic Chart and the corresponding Facing Page.

CODE 32 EXHAUST GAS RECIRCULATION (EGR) SYSTEM FAILURE 2.5L (VIN U) -N- CARLINE (TBI)

Circuit Description:

A properly operating EGR system will directly affect the air/fuel requirements of the engine. Since the exhaust gas introduced into the air/fuel mixture is an inert gas (contains very little or no oxygen), less fuel is required to maintain a correct air/fuel ratio. If the EGR system were to become inoperative, the inert exhaust gas would be replaced with air and the air/fuel mixture would be leaner. The ECM would compensate for the lean condition by adding fuel, resulting in higher block learn values.

The engine control system operates within two block learn cells, a closed throttle cell, and an open throttle cell. Since EGR is not used at idle, the closed throttle cell would not be affected by EGR system operation. The open throttle cell is affected by EGR operation and, when the EGR system is operating properly, the block learn values in both cells should be close to being the same. If the EGR system was inoperative, the block learn value in the open throttle cell would change (become higher) to compensate for the resulting lean system, but the block learn value in the closed throttle cell would not change.

This change or difference in block learn values is used to monitor EGR system performance. When the change becomes too great, a Code 32 is set.

Diagnostic Aids:

The Code 32 chart is a functional check of the EGR system. If the EGR system works properly, but a Code 32 has been set, check other items that could result in high block learn values in the open throttle cell, but not in the closed throttle cell.

CHECK:

EGR Passages

Restricted or blocked

MAP Sensor

A MAP sensor may shift in calibration enough to affect fuel delivery. Use CHART C-lD, MAP output check.

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.