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The following diagnosis might be helpful if the vehicle exhibits the symptom described in the PI.
Customer concern of poor acceleration, detonation or "ping" at idle in drive or reverse, and/or possible DTC P0101, P0106 and/or P0121 set in the PCM. The vehicle will perform properly after attaining a speed of about 30 - 40 mph. The condition may also be described by the customer or the dealer as a hesitation, stall when putting into gear, surge on accel (similar to hitting fuel cut or rev limit). The ultimate cause may be a non-holding torque converter stator or damaged stator support shaft within the automatic transmission.
The following checks should be performed in the event that normal engine driveability checks have not resolved the detonation or "ping" at idle in drive or reverse, lack of power from a stop, stall, surge on accel and or hesitation complaint . The transmission oil cooler outlet line (line to the cooler) should be checked for excessive heat. The Tech 2 scan tool may be helpful on vehicles equipped with the transmission fluid temperature sensor in the cooler line (mainly front wheel drive) . On vehicles that do not have the temperature sensor in the cooler line, a temperature probe should be used to check the temperature. The temperature readings should be compared to a like vehicle with the same powertrain option content. In the event the engine is not producing sufficient power the transmission oil temperature at the outlet cooler line will not be excessive and should compared closely to the like vehicle.
In the event the transmission torque converter stator or stator support are damaged, the transmission oil temperature at the outlet cooler line will be excessive to that of a like vehicle. A stall test (brake torque) may point to a damaged torque converter, the stall RPM speed will be lower then a like vehicle. However, poor engine performance will also produce a lower stall speed RPM. If the torque converter stator or stator support is suspect, the transmission should be removed and the stator support inspected for spline damage. If the stator support splines are damaged, the transmission should be repaired and new torque converter installed. If damage is not present on the stator support, the concern is either internal to the torque converter stator or an engine performance concern.
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Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance.
(96 - 05 All General Motors Passenger Cars and Light Duty Trucks)
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GM bulletins are intended for use by professional technicians,
NOT a "do-it-yourselfer". They are written to inform these
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 your GM dealer for information on whether
your vehicle may benefit from the information. |
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