INTERMITTENT LACK OF POWER ON ACCEL.-NEW PCM CALIBRATION. Saturn Saturn 1991

For 1990-2009 cars

# INTERMITTENT LACK OF POWER ON ACCEL.-NEW PCM CALIBRATION

#### SUBJECT: Intermittent Lack of Power on Acceleration and a Possible EC Information Flag 53 (New PCM Calibration) 1991 Saturns w/ SOHC (LKO) Engines

#### CONDITION:

---------- Some owners of Saturns may comment on vehicle intermittently having a lack of power when pulling away from a stop.

#### CAUSE:

------ When the knock sensor senses knock over a period of time, it begins to learn spark retard and fill the HI, MID and LOW spark tables. When these spark tables become full (each spark compensation table reading = 50) engine timing will be fully retarded causing a lower than normal power condition. An engine controller (EC) Information Flag 53 may or may not set. The noise that the knock sensor picks up most likely is not spark knock, but noise from another source that may be a normal noise.

#### CORRECTIVE ACTION:

Verify that no other codes are stored and that all PDT and Scan tool parameters are within specification. Verify that there are no audible noises such as a lifter ticking, a noisy accessory drive belt tensioner, etc., then download the new service calibration "Production/Lack of Power/EC Flag 53."

#### PROCEDURE:

---------- Perform the following steps:

1. Verify with the PDT or Scan tool that no other Codes or Information Flags are stored in Malfunction History. If Codes or Information Flags other than EC Information Flag 53 are stored, refer to the "Electronic Engine Controls Service Manual" for diagnosis steps. If there are no Codes or Information Flags stored, or only EC Information Flag 53 is stored, go to Step 2.

2. Verify that all PDT and Scan tool readings are within specification. Refer to the "Scan Tool General Information" tables in the "Electronic Engine Controls Service Manual." If the readings are within specification, go to Step 3. If any readings are not within specification, refer to "Description and Operation" in the "Electronic Engine Controls Service Manual." When all readings are within specification, go to Step 3.

3. Verify that there are no audible noises. If there is an audible noise, correct the source of the noise before the new calibration is downloaded. If there are no audible noises, go to Step 4.

4. If nothing was found in Steps 1-3, download the new calibration. Refer to the "Electronic Engine Controls Service Manual" or the "Service Stall System (SSS) User Guide" for proper recalibration procedures.

#### IMPORTANT: Before installing a new calibration, make a note of the transaxle calibration installed and download the same transaxle calibration with the correct new engine calibration. The new service PCM calibrations are:

#### New Calibration

1578 Automatic Transaxle (Production release)

1579 Automatic Transaxle (Use when idler gear noise calibration is installed)

1580 Manual Transaxle

IMPORTANT-. This calibration will replace the production calibration. The service stall system screen should read "Production Calibration/Lack of Power/EC Flag 53."

Only vehicles built with the latest PCM can be reprogrammed with the new calibraiion. Vehicles with earlier versions of the PCM require replacement of the PCM before reprogramming.

To determine if the PCM can be reprogrammed with this service calibration, check the TCM ID TABLE with the portable diagnostic tool (PDT) or the service stall system. If the TC EPROM SW ID is 4666 the PCM will have to be replaced. The new version of the PCM will have a TC EPROM SW ID of 1465.

If the PCM has to be replaced, refer to the "Powertrain Control Module" removal and installation procedures in the "Powertrain Control Module" section of the "Electronic Engine Controls Service Manual."

If the TC EPROM SW ID is 1465, refer to "Reprogramming EEPROM" in the "System Utilities" section of the "Service Stall System (SSS) User Guide" for procedures on reprogramming with the service calibration.

5. After the recalibration, verify on the PDT that the spark table values are all "O". View the HI, MID and LOW values under the spark table. If the spark values are not all "O", disconnect the battery for 10 seconds, then verify that the values are now all "0".

#### IMPORTANT: Due to the calibration change, Info. Flag 53 may set under normal conditions. If it does set, it should not be addressed unless there is a driveability concern.

#### CLAIM INFORMATION:

To receive credit for this repair, submit a claim through the Saturn Dealer System as follows: Labor Case Operation Type Description Code Time ---- ------------------------ --------- ------- VW Lack of Power/EC Flag 53 T9548 0.5 hrs PCM Recalibration (Includes PDT Checks) VW PCM Replacement T9550 0.3 hrs

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.