Diagnosis - Torque Converter Clutch GMC S15 Pickup

INTRODUCTION

Note. This article contains test charts that are required to test Torque Converter Clutch (TCC) system. Other diagnostic codes may appear while performing TCC electrical diagnosis. For complete information, see appropriate article in ENGINE PERFORMANCE.

The Torque Converter Clutch (TCC) assembly consists of a 3-element torque converter with the addition of a converter clutch. The converter clutch is an internal mechanism with friction material attached to front face. It is splined to the turbine assembly in converter. (Scheme 61)

The purpose of the automatic transaxle torque converter clutch feature is to eliminate power loss of torque converter stage when vehicle is in a cruise condition. This allows the convenience of an automatic transmission and the fuel economy of a manual transmission.

When the TCC solenoid is activated, the torque converter clutch is applied which results in a straight through mechanical coupling from engine to transmission. When TCC solenoid is deactivated, the torque converter clutch is released which allows the torque converter clutch to operate in a conventional manner.

Scheme 61

On-Board Diagnostics

The ECM of computerized engine control system is equipped with a self-diagnostic system which detects system failures or abnormalities.

TORQUE CONVERTER CLUTCH CONTROL COMPONENTS

The following components are used to engage/disengage torque converter control clutch. Not all components will be present on all vehicles.

1. Brake Switch The brake switch releases converter clutch when brakes are applied to prevent engine from stalling.
2. Coolant Temperature Sensor This sensor provides the ECM with engine coolant temperature information. The ECM will not allow TCC operation until signal from this sensor indicates coolant temperature higher than 130°-150°F (55°-65°C).
3. Electronic Control Module (ECM) The ECM receives and processes inputs from vehicle speed sensor, coolant temperature sensor, throttle position sensor, 3rd or 4th gear switch, and brake switch to determine application of torque converter clutch. The ECM controls application of torque converter clutch by grounding TCC solenoid circuit.
4. Throttle Position Sensor (TPS) Provides the ECM with throttle position information. TCC operation is prevented below a specific signal level.
5. 3rd & 4th Gear Switch The 3rd and 4th gear switches prevent TCC operation until direct drive (3rd and/or 4th gear) is obtained.
6. Vehicle Speed Sensor (VSS) This sensor sends vehicle speed information to ECM. Vehicle speed must be above a certain value before TCC can be applied. This sensor is located in the instrument cluster, behind speedometer.

BODY CONTROL MODULE

For location of Body Control Module (BCM), see appropriate COMPONENT LOCATIONS article.

ENGINE CONTROL MODULE

For location of Engine Control Module (ECM), see appropriate COMPONENT LOCATIONS article.

BRAKE SWITCH

Note. On Corvette, use light duty truck brake switch adjustment procedure. See LIGHT DUTY TRUCKS .

Passenger Cars

Insert switch into tubular clip until switch body seats on clip. Pull brake pedal fully rearward against internal pedal stop. Switch will be moved into tubular clip, providing proper adjustment.

Light Duty Trucks

Depress brake pedal and press switch in until firmly seated in clip. Audible "clicks" should be heard as threaded portion of switch is pushed through clip. Pull brake pedal against pedal stop until "click" can no longer be heard.

THROTTLE POSITION SENSOR (CARBURETED MODELS ONLY)

1. Ensure that engine idle speed is correct. On 2.8L engine equipped vehicles, disconnect TPS connector and jumper all 3 terminals. On all models, connect digital voltmeter from TPS connector center terminal to bottom terminal.
2. Turn ignition on, DO NOT start engine. On 2.8L engine equipped vehicles, ensure that A/C is off and that throttle kicker solenoid is fully retracted. On all other models, disconnect electrical connector from idle solenoid and let throttle lever rest against idle speed screw.
3. On all models, read TPS voltage. If reading is incorrect, use a 5/64" drill bit and carefully drill a hole in plug covering TPS adjustment screw. Plug is located next to TPS plunger bore. Start a No. 8, 1/2" long self-tapping screw in drilled hole turning screw in only enough to ensure good thread engagement.
4. Place a screwdriver between screw head and carburetor air horn casting, pry against screw head to remove plug. With ignition on, engine stopped; turn TPS adjustment screw to obtain specified voltage. (Scheme 62)and «THROTTLE POSITION SENSOR VOLTAGE»(/gmc/s15-pickup/1985-1988/remont/automatic-trans/#diagnosis-torque-converter-clutch). After adjustment, a new plug or RTV sealant must be inserted in TPS adjustment screw hole.

THROTTLE POSITION SENSOR VOLTAGE (1)

Scheme 62

SELF-DIAGNOSTIC SYSTEM

Note. Special SCAN testers can be used to read trouble codes and check voltages in the system. These tools can save a great deal of time, but are not required. Refer to tester's manufacturer manual for operating procedures. Also see scan portion of test chart(s).

DIAGNOSTICS TOOLS

The TCC system does not require special tools for diagnosis. A tachometer, a test light, ohmmeter, digital voltmeter with 10 megohms impedance (minimum), and 6 jumper wires 6 long (1 wire with female connectors at both ends; 1 wire with male connector at both ends; 4 wires with male and female connectors at opposite ends) are the only tools necessary for diagnosis. A test light, rather than a voltmeter, must be used when indicated by a diagnostic chart(s).

RETRIEVING DIAGNOSTIC TROUBLE CODES

Note. It will be necessary to enter service mode to use Riviera and Toronado TCC test chart(s). Enter appropriate test condition (i.e. ECM INPUTS, BCM CODE, etc.) as indicated in chart(s).

Note. Operating vehicle in service mode for extended periods of time will cause the battery to run down and possibly relate false diagnostic information. Connect battery charger on trickle charge if vehicle is to be in service mode for periods longer than 1/2 hour.

Entering Diagnostic Mode (Buick Riviera)

Turn ignition on. Touch the OFF and WARM key pads on, the Cathode Ray Tube (CRT) climate control page simultaneously and hold until a double beep is heard or a page entitled SERVICE MODE appears on the screen. (Scheme 63)

Entering Diagnostic Mode (Oldsmobile Toronado)

Turn ignition on. Touch the OFF and WARM buttons on the ECC control panel simultaneously, and hold until a segment check is displayed on the Instrument Panel Cluster (IPC) and Electronic Climate Control (ECC) panel. (Scheme 64)

Scheme 63

Scheme 64

Entering Diagnostic Mode (Except Buick Riviera & Oldsmobile Toronado)

The ECM stores component failure information under a related trouble code which can be recalled for diagnosis and repair. When recalled, these codes will be displayed by flashes of the CHECK ENGINE/SERVICE ENGINE SOON light.

It is NOT necessary to enter diagnostic mode to use TCC test chart(s). It will be necessary to enter ECM diagnostic mode to verify the presence of Code 24, Codes 33 and 34 (4.3L TBI passenger car engine).

1. To enter diagnostic mode, turn ignition on but do not start engine. CHECK ENGINE/SERVICE ENGINE SOON light should glow. Locate Assembly Line Communication Link (ALCL) connector attached to ECM wiring harness under instrument panel. Insert jumper wire across diagnostic mode test terminal "B" and ground terminal "A". (Scheme 65)
2. CHECK ENGINE/SERVICE ENGINE SOON light should flash Code 12 (FLASH, pause, FLASH, FLASH ) followed by a longer pause. Trouble Code 12 will be repeated 3 more times, then if any trouble codes are stored in the ECM memory, they will be displayed in the same manner.
3. Trouble codes will be displayed from lowest to highest numbered codes (3 times each) and be repeated as long as the TEST terminal of the ALCL connector is grounded.
4. To exit diagnostic mode, turn ignition off and remove jumper wire from ALCL connector.

ALCL Connector Terminal Identification. Scheme 65

Buick Riviera

After service mode is entered any trouble codes stored in the computer memory will be displayed. See ECM & BCM TROUBLE CODE DEFINITION . ECM codes will be displayed first. If no ECM codes are stored, the CRT will display NO ECM CODES for approximately 2 seconds.

After ECM codes have been displayed, the BCM codes will be displayed. BCM codes will also be accompanied by Current or History. History indicates that the failure was not present when last tested. Current indicates the fault still exists.

If no BCM codes are present, the BCM will display NO BCM CODES message. Trouble codes for both the ECM and BCM will be displayed in numerical succession of lowest too highest numbered code.

Oldsmobile Toronado

After service mode is entered, any trouble codes stored in the computer will be displayed. See ECM & BCM TROUBLE CODE DEFINITIONS . ECM codes will be displayed first. If no ECM codes are stored, the IPC will display NO ECM CODES . All ECM codes will be prefixed by an "E" (i.e. E013).

When all ECM codes have been displayed, the BCM codes will be displayed. BCM codes mainly deal with body control functions, with climate control being one of its main features. BCM codes are prefixed with an "B" (i.e. B110). BCM codes can also be accompanied by CURRENT , indicating that the fault still exists. If no BCM codes exist, NO BCM CODES message will be displayed.

Both ECM and BCM codes are displayed in 2 second intervals starting at the lowest numbered code and ending at the highest. If the LO fan- button is pressed anytime during the display of ECM and BCM codes, the display of codes will be by-passed. If at any time the BI-LEV button is pressed, the BCM will exit the service mode and go back to normal vehicle operation.

ECM & BCM TROUBLE CODE DEFINITIONS (BUICK RIVIERA & OLDSMOBILE TORONADO)

ECM & BCM TROUBLE CODE DEFINITION

DIAGNOSTIC TROUBLE CODE DEFINITIONS

DIAGNOSTIC TROUBLE CODE DEFINITIONS

After trouble codes have been displayed, the service mode can be used to perform several tests on different systems one at a time. Upon completion of the trouble code display, a specific system may be selected for testing. Following the trouble code display, the first available system will be displayed (i.e. ECM). When making system selections there are 3 available alternatives

1. Pressing the EXIT key pad will stop the system selection process and return to the beginning of the trouble code sequence.
2. Pressing the NO key pad will display the next available system selection.
3. Pressing the YES key pad will select the displayed system for testing.

After trouble codes have been displayed, the service mode can be used to perform several tests on different systems one at a time. Upon completion of trouble code display, a specific system may be selected for testing. Following trouble code display, the first available system will be displayed (i.e. ECM). When selecting a test, there are 4 available actions to be taken

1. Pressing the OFF button will stop the system selection process and return the display to the beginning of the trouble code sequence.
2. Pressing the LOW fan button will display the next available system selection. This allows all system selections to be displayed.
3. Pressing the HIGH fan button will select the displayed system for testing.
4. Pressing the BI-LEV button will exit diagnostics and return to normal IPC and ECC operation.

Having selected a system, the first available test type will be displayed (i.e. ECM DATA ). When making selection of test type there are 3 available alternatives

1. Pressing the EXIT key pad will stop the test type selection and return the display to the next available system selection.
2. Pressing the NO key pad will display the next available test type for the selected system. This allows the display to be stepped through all available test type choices.
3. Pressing the YES key pad will select the displayed test type. Here, the display will either indicate that the selected test type is in progress or the first of several specific tests will appear. If NO DEVICES appears, no test is available.

Having selected a system, the first available test type will be displayed (i.e. ECM DATA ). When selecting a specific test type there are 4 available actions to be taken

1. Pressing the OFF button will stop the test type selection process and return to the next available selection.
2. Pressing the LOW fan button will display the next available test type for the selected system. This allows all available test types to be displayed for selection.
3. Pressing the HIGH fan button will select the displayed test type. Here the display will either indicate whether the selected test type is in progress or the first of several tests will appear.
4. Pressing the BI-LEV button will exit diagnostics.

Selection of DATA, INPUTS, OUTPUTS, or OVERRIDE test types will result in the first available test being displayed. If a Select ERR message appears, this test is not allowed with the engine running. Turn engine off and try again. (Scheme 66)

Four characters of the display will contain a test code to identify the selection. The first 2 characters are letters which identify the system and test type (i.e. ED for ECM DATA), while the last 2 characters numerically identify the test. When selecting these tests, 3 alternatives are available

1. Pressing the EXIT key pad will stop the test selection process and return the display to the next test type for the selected system.
2. Pressing the NO key pad will display the next smaller test number. If the lowest number is already displayed, the highest number will then be displayed.
3. Pressing the YES key pad will display the next larger test number for the selected test type. If the highest number is already displayed, the lowest number will appear.

Scheme 66

Selection of DATA, INPUTS, or OUTPUTS test types will result in the first available test being displayed. If the message, EEEE appears it means that test is not allowed with the engine running. Turn engine off and repeat sequence. (Scheme 67)

The last 4 characters of the display will contain a test code to identify the selection. The first 2 of these characters are letters which identify the system and the test type (i.e. ED for ECM DATA ), while the last 2 characters numerically identify the test. When selecting a specific test there are 3 available actions to be taken

1. Pressing the OFF button will stop the test selection process and return the display to the next available test type for the selected system.
2. Pressing the LOW fan button will display the next smaller test number for the selected test type.
3. Pressing the HI fan button will display the next larger test number for the selected test type.

Upon selection of an OVERRIDE test function, current operation will be represented as a percentage of its full range. This value will be displayed on the ECC panel. The display will alternate between "--" and the normal program value. This alternating display is a reminder that the function is not currently being overridden.

Pressing the WARM or COOL buttons on the ECC panel begins the override, at which time the display will no longer alternate. Pressing the WARM button increases the value while pressing the COOL button decreases the value. Normal program control can be resumed in 1 of 3 ways.

1. Selection of another override test will cancel the current override.
2. Selection of another system (i.e. ECM, BCM) will cancel the current override.
3. Overriding the value beyond either extreme (0 or 99) will display "--" momentarily and then jump to the opposite extreme. If the button is released while "--" is being displayed, normal program control will resume and the display will again alternate.

The override test type is unique in that any other test type within the selected system may be active at the same time. After, selecting an override test, pressing the OFF button will allow selection of another test type, DATA; INPUTS or OUTPUTS. The ECC panel will continue to display the selected override. By selecting another test type and test, while at the same time pressing the WARM or COOL button, it is possible to monitor the effect of the override on different vehicle parameters.

Scheme 67

Except Buick Riviera & Oldsmobile Toronado

Trouble codes are cleared by removing battery voltage from ECM for at least 10 seconds. Turn ignition off and remove ECM fuse from fuse block for 10 seconds. Remove TEST lead ground.

Clear Codes Selection (Buick Riviera)

Selection of CODE RESET test type, it will result in the message CODES CLEAR being displayed with the selected system name above it after the YES pad has been touched. This message appears for 3 seconds to indicate that all stored trouble codes have been erased from memory. After this 3-second interval, the system will automatically return to the next available test type for the selected system.

Clear Codes Selection (Oldsmobile Toronado)

Selecting reset codes will result in the message CLEAR ECM CODES or CLEAR BCM CODES being displayed, depending on which system was being tested. At this time the following action may be taken

1. Pressing the OFF button will stop the test selection process and return the display to the next available test type for the selected system.
2. Pressing the LOW fan button will display the next test type.
3. Pressing the HIGH fan button will select CLEAR CODES. A message ECM CODES CLEARED or BCM CODES CLEARED will appear to indicate those codes have been cleared from memory.
4. Pressing the BI-LEV button will exit diagnostics.

Existing Service Mode (Buick Riviera)

To exit service mode, repeatedly press the EXIT key pad until the SERVICE MODE page disappears or turn ignition off. Trouble codes are not erase when this is done.

Existing Service Mode (Oldsmobile Toronado)

To exit service mode, press the BI-LEV button. Trouble codes are not erased when this is done. Any mode button will exit diagnostics, however, the BI-LEV button was chosen for consistency.

DIAGNOSTIC TESTS

Use the following test charts to diagnose the TCC electrical system. Make sure to use appropriate test charts. Using wrong test charts will result in TCC misdiagnosis. Some test steps will refer you to corresponding vehicle speed sensor (Code 24) and park/neutral switch test charts.

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Scheme 100

When trouble shooting a malfunction, the ECM and BCM data display can be used to compare the vehicle with problems, with a vehicle that is functioning properly When ECM data ED12 or BCM data BD60 is entered, vehicle speed is displayed from "0" (zero) to 159 MPH. See ECM DATA & BCM DATA DISPLAY CODE DEFINITION .

ECM DATA & BCM DATA DISPLAY CODE DEFINITION

INPUT DISPLAYS

When trouble shooting a malfunction, the ECM, BCM, or IPC input display can be used to determine if the switched inputs are properly interpreted. When one of the input tests is selected, the state of that device is displayed as HI or LO. Basically, HI or LO represent the input terminal voltage for that circuit. The display also indicates if the input changed state since it was last tested. If a change occurred, an "X" will appear next to the HI/LO indicator. On Riviera, if a change did not occur, a "0" will remain displayed. The "X" will only appear once per selected input. When input display E182 is entered, the 4th gear switch is HI when vehicle is in 4th gear. See ECM INPUT DISPLAY CODE DEFINITION .

ECM INPUT DISPLAY CODE DEFINITION

OUTPUT DISPLAYS

When trouble shooting a malfunction, the ECM and BCM output cycling can be used to determine if output tests can be actuated regardless of the inputs and normal program instructions. Once a test in outputs is selected, except for ECM IAC, the test will display HI or LO for 3 seconds in each state to indicate the command and output terminal voltage. When ECM output EO02 is entered, the torque converter clutch display will be LO when TCC is on (energized). See ECM OUTPUT DISPLAY CODE DEFINITION .

ECM OUTPUT DISPLAY CODE DEFINITION

CONNECTOR IDENTIFICATION

For aid in diagnosis use connector and terminal views in test chart procedures. See DIAGNOSTIC TESTS .

WIRING DIAGRAMS

Note. For further aid in identification of circuits, terminals and wire colors, see appropriate wiring diagram in WIRING DIAGRAMS article.

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See also:
• LIGHT DUTY TRUCKS
• THROTTLE POSITION SENSOR VOLTAGE
• ECM & BCM TROUBLE CODE DEFINITIONS
• DIAGNOSTIC TESTS