SERVICE MANUAL UPDATE TRANSAXLE DIAGNOSIS PROCEDURE

SUBJECT: SERVICE MANUAL UPDATE - TRANSAXLE DIAGNOSIS-UPDATED PAGES 15 THROUGH 22,61 AND 62 VOLUME 2

MODELS/YEARS: 1991 CUTLASS SUPREME

Some incorrect pages were printed in the 1991 Cutlass Supreme Service Manual, Volume 2, within the "Automatic Transaxle Diagnosis Hydra-Matic 4T60-E" section. The pages that follow replace identically numbered pages in the above service manual.

Please mark a reference to this bulletin in your copy(s) of the 1991 Cutlass Supreme Service Manual, Volume 2, on the affected pages.

MANUALLY SHIFTING THE TRANSAXLE

Place vehicle on hoist, secure and raise so drive wheels clear the floor (9-1 2 inches). Allow clearance for vehicle to safely operate on hoist and for technician to work on vehicle. Two persons are needed to perform the following tests.

4TH GEAR OPERATION:

1. Repeat step 6 then start vehicle and let run, then shift to D4 range. Ground lead F, transaxle should be in 4th gear. Engine R.P.M. should be about 900 and M.P.H. should be about 19-20. Remove probe.

3RD GEAR OPERATION:

2. Disconnect groundand transaxle should downshift to 3rd gear. M.P.H. should be 2-4 miles lower than M.P.H. in 4th gear. Remove ground.

2ND GEAR OPERATION:

3. Connect ground to wire G, transaxle should downshift into 2nd gear. M.P.H. should be about 3-5 lower than 3rd gear. Remove ground.

1ST GEAR OPERATION:

4. Connect wires F and G and connect ground, transaxle will shift into first gear. M.P.H. should be about 3-5 M.P.H. lower than 2nd gear. Remove ground.

TCC TEST

1. Shift transaxle to D3 range with the wire harness to the transaxle disconnected and foot on brakes. While brakes are applied connect probe to wire D, TCC will apply and engine must stall. Remove probe.

V.S.S. TEST (Vehicle Speed Sensor) ---------------------------------- If VSS is inoperative there may be no speedometer readout on the instrument cluster when the transmission is in one of the drive ranges and moving forward. The symptom most likely to occur will be 3rd gear range under most conditions, or Code 24.

TO TEST V.S.S.:

1. Secure and raise the vehicle. Put transaxle in neutral, turn key off.

2. Remove the female connector that plugs into the sensor. (Note and identify the wires from the vehicle for the ground and positive feed into the sensor.

3. Using a DVM, connect positive and negative leads to the VSS at the appropriate pins.

4. Turn the meter to the ACV 2 volt position.

5. By hand, spin drive wheel closest to VSS from a slow to moderate rate. A readout will be given in volts and will vary depending upon rate the wheel is spinned.

The voltage should always increase in a linear fashion.

When VSS is disconnected from the vehicle it becomes an AC generator.

PCM INPUTS THAT AFFECT THE 4T60-E (3.4L AND 4T60-E POWERTRAIN) -------------------------------------------------------------- THROTTLE POSITION SENSOR ------------------------- o MEASURES THE THROTTLE POSITION AND INPUTS IT INTO THE PCM o PROVIDES DATA TO DEVELOP THE SHIFT PATTERN o THERE ARE TWO DIAGNOSTICS ASSOCIATED WITH THE SENSOR CODE 21 THROTTLE POSITION SENSOR TOO HIGH CODE 22 THROTTLE POSITION SENSOR TOO LOW

THE FAILSAFE ACTIONS ARE: o OFF MODE OF THE TCC o INHIBIT 4TH GEAR o USE DEFAULT VALUE FOR TPS IT WILL RECOVER ON THE NEXT IGNITION

VEHICLE SPEED SENSOR

o MEASURES THE SPEED OF THE FINAL DRIVE ASSEMBLY o PROVIDES DATA TO DEVELOP THE SHIFT PATTERN o GENERATES A VOLTAGE WAVEFORM AND ITS FREQUENCY DETERMINES VEHICLE SPEED o THERE IS ONE DIAGNOSTIC ASSOCIATED WITH THE SENSOR CODE 24 VEHICLE SPEED SENSOR DETECTS WHEN THE SIGNAL IS TOO LOW DETECTS A LARGE DROP IN SPEED THE FAILSAFE ACTIONS ARE: o TCC WILL NOT OPERATE o THE PCM WILL FORCE THIRD GEAR o USES LAST GOOD VALUE AS DEFAULT VARIABLE IT WILL RECOVER ON THE NEXT IGNITION

ENGINE COOLANT TEMPERATURE

o MEASURES THE ENGINE COOLANT TEMPERATURE o THE PCM WILL NOT COMMAND THE TCC UNTIL THE ENGINE COOLANT TEMPERATURE IS ABOVE A SPECIFIC TEMPERATURE 65 C (149 F) [TCC ON ABOVE 150 C (302 F) TO AID COOLING] o THERE ARE TWO DIAGNOSTICS ASSOCIATED WITH THIS SENSOR CODE 14 COOLANT TEMPERATURE SENSOR HIGH CODE 15 COOLANT TEMPERATURE SENSOR LOW THE FAILSAFE ACTIONS ARE:

o A DEFAULT VALUE IS USED AND IT IS A FUNCTION OF ENGINE RUNNING TIME o ALLOWS TCC OPERATION IT WILL RECOVER UPON A VALID RANGE

4T60-E SOLENOIDS USED WITH THE 3.4L ------------------------------------ SHIFT SOLENOID A ---------------- o IS ELECTRONICALLY CONTROLLED BY A ODM LOCATED IN THE PCM o IS AN ELECTRONIC NORMALLY OPEN EXHAUST VALVE o WHEN ACTIVATED, IT REDIRECTS THE EXHAUSTING FLUID TO ACT UPON THE 1-2 AND 3-4 SHIFT VALVES o ON IN 1ST AND 4TH GEAR AND OFF IN 2ND AND 3RD GEAR o THERE ARE NO MALFUNCTION CODES ASSOCIATED WITH THIS SOLENOID

SHIFT SOLENOID B

o IS ELECTRONICALLY CONTROLLED BY A QDM LOCATED IN THE PCM o IS AN ELECTRONIC NORMALLY OPEN EXHAUST VALVE o WHEN ACTIVATED, IT REDIRECTS THE EXHAUSTING FLUID TO ACT UPON THE 1-2, 2-3 AND 3-4 SHIFT VALVES o ON IN 1ST AND 2ND GEAR AND OFF IN 3RD AND 4TH GEAR o THERE ARE NO MALFUNCTION CODES ASSOCIATED WITH THIS SOLENOID

TCC SOLENOID

o IS ELECTRONICALLY CONTROLLED BY A QDM LOCATED IN THE PCM o IS AN ELECTRONIC NORMALLY OPEN EXHAUST VALVE o WHEN ACTIVATED, IT REDIRECTS THE EXHAUSTING FLUID TO ACT UPON THE TCC SHIFT VALVE o CONTROLLED IN 3RD AND 4TH GEAR TO APPLY TCC o SUPPLIED BY IGNITION THROUGH THE BRAKE SWITCH o THERE ARE NO MALFUNCTION CODES ASSOCIATED WITH THIS SOLENOID

CRUISE CONTROL

o WHEN ENGAGED ALTERS THE SHIFT PATTERN TO REDUCE THE NUMBER OF 3-4 AND 4-3 SHIFTS A TIME LIMIT MUST BE MET BETWEEN 3-2 AND A 2-3 SHIFT A TIME LIMIT MUST BE MET BETWEEN 4-3 AND A 3-4 SHIFT

ENGINE SPEED

o DETERMINED BY DISTRIBUTOR REFERENCE PULSES o USED FOR THE KICKDOWN SHIFT PATTERNS

BRAKE SWITCH

o POWER IS ROUTED THROUGH THE BRAKE SWITCH TO THE TCC SOLENOID o DISENGAGES THE TCC SOLENOID FROM THE POWER FEED WHEN THE BRAKE IS APPLIED

LOW GEAR PRESSURE SWITCH

o NORMALLY OPEN SWITCH THAT DETECTS LINE PRESSURE IN LOW GEAR o INPUTS DIRECTLY INTO THE PCM o INFORMS THE PCM THAT LO GEAR HAS BEEN SELECTED SO THE PCM CAN ACTUATE BOTH SOLENOIDS TO ACHIEVE LO GEAR

FOURTH GEAR PRESSURE SWITCH

o NORMALLY OPEN SWITCH THAT DETECTS LINE PRESSURE IN FOURTH GEAR o INPUTS DIRECTLY INTO THE PCM o NOTIFIES THE PCM TO DISABLE TCC TO ELIMINATE A HARSH DOWNSHIFT DURING MANUAL D4-D3 DOWNSHIFTS

MANIFOLD AIR PRESSURE SENSOR

o MEASURES THE AIR PRESSURE AND ALTITUDE o USED TO MODIFY THE POINT AT WHICH THE TRANSMISSION WILL SHIFT

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.