Engine Controls - Driveability/Codes 23, 25, 33, 34

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NUMBER: 88-T-147A

CORP.REF.NO: 936518R

DATE: September 1989

SECTION: 6E


SUBJECT:

DRIVEABILITY CONDITIONS AND/OR STORED
ENGINE CODES 23,25, 33 OR 34, - 2.8L ENGINE
(PROCEDURE AND PROM)

MODELS/YEARS:

1987 FIRENZA, 1987-88 CUTLASS CIERA AND 1988
CUTLASS SUPREME


This bulletin cancels and supersedes Dealer Technical Bulletin 88-T-1 47.

This bulletin has been revised to change the MEM-CAL Part Number for the 1988 Cutlass Supreme with 4-speed automatic transaxle and California emission and to change the last paragraph additional information after changing the MEM-CAL.

Some customers with an engine/vehicle combination listed below

1987 Firenza Models With a 2.8L Engine (Vin Code W)
1988 Cutlass Supreme Models With a 2.8L Engine (Vin Code W)
1987-88 Cutlass Ciera Models With a 2.8L Engine (Vin Code W)

may comment that they have experienced one or more of the following conditions:

A cold start stall or sag

A decel stall

A tip-in hesitation

A check engine light with stored Codes 23, 25, 33, 34 or

An engine speed flare during a declutch operation with a manual transmission equipped vehicle.

These conditions may be attributed to a number of components/interactions. In the interest of simplifying diagnosis and repair, the following procedure has been developed to reduce system sensitivity, thereby addressing a variety of potential causes simultaneously.

If a customer comment concerning an occasional engine stall or a drive hesitation is received, and/or a stored Code 33 or 34 is found, then complete the following procedure:

1 . Perform diagnostic procedures per Section 6E of the Service Manual, and correct any faults except for Codes 33, 34, 23 or 25. If the diagnostics indicate the Mass Air Flow (MAF) is to be replaced or a Code 33 or 34 is present, DO NOT REPLACE THE MAF SENSOR! Proceed to Step # 3. If a Code 23 or 25 is present, go to Step # 2 below. PROCEED TO STEP # 3 ONLY IF NORMAL DIAGNOSTIC CHECKS DID NOT IDENTIFY A CAUSE FOR THE CUSTOMER CONCERN.

2. If a Code 23 or 25 is stored, perform the model year diagnostics for the Manifold Air Temperature
Sensor (MAT). If the diagnostics indicate that the MAT is faulty and replacement is required, replace the combination MAT/MAF sensor. Proceed to Step # 3.

3. Install a new MEM-CAL into the Engine Control Module (ECM) per instructions below. The new MEM-CAL Is available from GMSPO. See attached service part number chart. Install the identification label package to the ECM access door and to the left shock tower per label kit, P/N 10154725 Instructions.


IMPORTANT:
The new MEM-CAL to be installed does not need or use the existing MAF signal; however, it does need and use the MAT signal.


A). Pull the underhood ECM continous power fuse or disconnect the battery and leave it
disconnected for at least I0 minutes.

B). Remove MAF relay, If applicable, and discard. Tape up connector to prevent water intrusion.

C). Remove current MEM-CAL and install a new service MEM-CAL.

D). Restore the battery power and place air conditioning controls (if equipped) in the "off" position.

E). Firmly apply the parking brake and block the drive wheels. Start the engine, and shift the transaxle to "drive" for automatics or "neutral" for manuals.

F). Allow the engine to run until the engine cooling fan has cycled once, or a maximum of 10 minutes.

G). Turn the Ignition key to the "off" position for at least 5 seconds.

H). Start the engine, and shift the tranaxle to "drive" for automatics or "neutral" for manuals.

I). Allow engine to run for at least 5 minutes.

After a MEM-CAL replacement, the 1987-88 2.8L Speed Density Driveability and Emissions Manual, (form number ST399-87/88 SDM), must be used for driveability and emissions diagnostics. To secure additional publications use order forms available to all dealers through Helm, Inc., or dial (313) 865-5000 and ask for customer service. Use 1989 model year and cartridge for scanner-type diagnosis.

WARRANTY INFORMATION

Use applicable labor operations and times.


Labor Operation Number: Tl492 for MEM-CAL change


Labor Time:

1987-88 Cutlass Ciera 1.0 Hour

1987 Firenza 0.9 Hour

1988 Cutlass Supreme 0.8 Hour


Trouble Code: 92


If combination MAF/MAT sensor replacement is necessary, use Labor Operation Number J5670.





MEM-CAL SELECTION CHART - SERVICE PART NUMBERS


IMPORTANT:
MEM-CAL MUST BE ORDERED WITH LABEL KIT, P/N 10154725


IMPORTANT:
Scan I.D.Is are of the MEM-CALS listed below.


Parts are expected to be available on July 17, 1989. Until then normal part orders will not be accepted by GMSPO. Only verifiable emergency VIP orders will be accepted. SPO will make every effort to obtain parts. All parts will be placed on 400 control to waive VIP surcharges. However, the part will be shipped premium transportation at dealer's expense. All other order types will be canceled as incorrectly ordered while the 400 control is in place.