FEATURES
The traction control system (TCL) is adopted for vehicles with 3.8L engine.
- When a drive wheel is judged to be slipping by some reasons such as excessive accelerator pedal depression on a low friction road, the TCL applies brake force to the slipping drive wheel or lowers the engine output to suppress the drive wheel slippage.
- Fail-safe function ensures safety is maintained
- Diagnostic function provides improved serviceability
- To shorten the lines and enhance data transaxle reliability, communication with other ECU is performed over a CAN (Controller Area Network).
Scheme 86
| NAME OF PART | NUMBER | OUTLINE OF FUNCTION | |
|---|---|---|---|
| Sensor | Wheel speed sensor | 1 | Sends alternating current signals at frequencies which are proportional to the rotation speeds of each wheel to the ABS/TCL-ECU. |
| Stoplight switch | 2 | Sends a signal to the ABS/TCL-ECU to indicate whether the brake pedal is depressed or not. | |
| TCL OFF switch | 3 | Sends a signal to the ABS/TCL-ECU to indicate whether the TCL OFF switch is pushed or not. | |
| Actuator | Hydraulic unit | 4 | Drives the solenoid valves according to signals from the ABS/TCL-ECU in order to control the brake hydraulic pressure for each wheel. |
| ABS warning light | 5 | Illuminates in response to signals from the ABS/TCL-ECU when a problem develops in the ABS/TCL system. | |
| Brake warning light | 6 | Illuminates in response to signals from the ABS/TCL-ECU when a problem develops in the EBD system. | |
| TCL indicator | 7 | Flashes when the TCL is activated. Illuminates when the ABS/TCL-ECU is defective. | |
| TCL OFF indicator | 8 | Illuminates when the TCL is OFF. Illuminates when the ABS/TCL-ECU is defective. | |
| Data link connector | 9 | Outputs the diagnostic trouble codes and allows communication with the scan tool. | |
| ABS/TCL-ECU | 10 | Controls actuators (described above) based on the signals coming from each sensor. | |
| Controls the self-diagnosis and fail-safe functions. | |||
| Controls the diagnostic function (scan tool compatible). | |||
| Engine control module (ECM)< M/T > | 11 | Receives signals from ABS/TCL-ECU to control the engine output. | |
| Powertrain control module (PCM)< A/T > | Controls the self-diagnosis and fail-safe functions. | ||
| Controls the diagnostic function (scan tool compatible). | |||
PART NUMBER CHART
SYSTEM CHECK SOUND
When starting the engine, a thudding sound can sometimes be heard coming from the engine compartment. This is a normal sound during the ABS/TCL self-check.
HOW TO READ DATA LIST
Required Special Tools
- MB991958: Scan Tool (MUT-III Sub Assembly) MB991824: V.C.I. MB991827: MUT-III USB Cable MB991910: MUT-III Main Harness A
| CAUTION | To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958. |
- Connect scan tool MB991958 to the data link connector.
- Turn the ignition switch to the "ON" position.
- Select "Interactive Diagnosis" from the start-up screen.
- Select "System Select."
- Choose "ABS/TCL" from the "CHASSIS" tab.
- Select "Data List."
- Choose an appropriate item and select the "OK" button.
COMMENT
This may be caused by faults in the CAN bus line, the combination meter or the ABS/TCL-ECU.
The cause is probably an open-circuit in the TCL switch circuit.
The fail-safe function is probably canceling TCL. In this case, scan tool MB991958 can be used to retest each system by checking the diagnostic trouble codes.
DATA LIST REFERENCE TABLE
The following items can be read by the scan tool from the ABS/TCL-ECU input data.
| MUT-III SCAN TOOL DISPLAY | ITEM NO. | CHECK ITEM | CHECKING REQUIREMENTS | NORMAL VALUE |
|---|---|---|---|---|
| FL wheel speed sensor | 01 | Front-left wheel speed sensor | Drive the vehicle | Vehicle speeds displayed on the speedometer and scan tool are identical. |
| FR wheel speed sensor | 02 | Front-right wheel speed sensor | ||
| RL wheel speed sensor | 03 | Rear-left wheel speed sensor | ||
| RR wheel speed sensor | 04 | Rear-right wheel speed sensor | ||
| Power supply voltage | 05 | ABS/TCL-ECU power supply voltage | Ignition switch power supply voltage and valve monitor voltage | Battery positive voltage |
| Stoplight switch (input) | 06 | Stoplight switch | Depress the brake pedal. | ON |
| Release the brake pedal. | OFF | |||
| TCL OFF switch | 28 | TCL switch | TCL switch: ON | ON |
| TCL switch: OFF | OFF |
DATA LIST REFERENCE CHART
TERMINAL VOLTAGE CHECK CHART
Required Special Tool
MB991997: ASC Check Harness
Scheme 87
- Disconnect the ABS/TCL-ECU connector A-03, and then use special tool MB991970 to measure the voltages between terminals (16 ) and each terminal other than terminal (47). Also measure voltages between terminal (47) and each terminal other than terminal (16). NOTE: Do not measure terminal voltage for approximately three seconds after the ignition switch is turned "ON." The ABS/TCL-ECU performs the initial check during that period.
- The terminal layouts are shown in the illustrations below.
| CONNECTOR TERMINAL NO | SIGNAL | CHECKING REQUIREMENT | NORMAL CONDITION | |
|---|---|---|---|---|
| 1 | Motor power supply | Always | Battery positive voltage | |
| 4 | ABS/TCL-ECU power supply | Ignition switch: "ON" | Battery positive voltage | |
| Ignition switch: "START" | Approximately 0 V | |||
| 32 | Solenoid valve power supply | Always | Battery positive voltage | |
| 38 | TCL switch input | Ignition switch: "ON" | TCL switch: "ON" | Battery positive voltage |
| TCL switch: "OFF" | Approximately 0 V | |||
| 41 | Stoplight switch input | Ignition switch: "ON" | Stoplight switch: "ON" | Battery positive voltage |
| Stoplight switch: "OFF" | Approximately 0 V | |||
CONNECTOR TERMINAL SIGNAL CHART
WHEEL SPEED SENSOR OUTPUT VOLTAGE MEASUREMENT
Required Special Tool
MB991219: Inspection Harness
Scheme 88
Scheme 89
- Release the parking brake and lift up the vehicle.
- Disconnect the ABS/TCL-ECU connector A-03, and then use special tool MB991219 to measure the output voltage at the harness side connector. WHEEL SPEED SENSOR OUTPUT VOLTAGE MEASUREMENT TERMINAL NO. Front left Front right Rear left Rear right 45 33 36 42 46 34 37 43
- Manually turn the wheel to be measured 1/2 to 1 turn/second. Measure the output voltage with a voltmeter or oscilloscope. NOTE: Check the connection of the sensor harness and connector before using the oscilloscope. Output voltage: Minimal voltmeter reading: 42 mV Maximum voltmeter reading: 300 mV Minimal oscilloscope reading: 120 mV Maximum oscilloscope reading: 600 mV Probable causes of low output voltage Wheel speed sensor pole piece-to-Wheel speed rotor clearance too large Faulty wheel speed sensor
- To observe the waveform with an oscilloscope: Front wheels: Shift into 1st gear < M/T > or "D" range < A/T > and drive the wheels. Rear wheels: Turn the wheels manually at a constant speed NOTE: The output waveform is low when the wheel speed is low. Similarly, it will be higher as the wheel speed increases. Waveform may also be observed by driving the vehicle.
POINTS IN WAVEFORM MEASUREMENT
| SYMPTOM | PROBABLE CAUSE | REMEDY |
|---|---|---|
| Too small or zero waveform amplitude | Faulty wheel speed sensor or excessive gap between it and the wheel speed rotor | Replace wheel speed sensor |
| Waveform amplitude fluctuates excessively (This is no problem if the minimum amplitude is 100 mV or more) | Axle hub eccentric or with large runout | Replace hub assembly |
| Faulty ABS/TCL-ECU ground | Repair harness wires | |
| Noisy or disturbed waveform | Open circuit in wheel speed sensor | Replace wheel speed sensor |
| Open circuit in harness | Repair harness wire | |
| Incorrectly mounted wheel speed sensor | Mount wheel speed sensor correctly | |
| Wheel speed rotor with missing or damaged teeth | Replace wheel speed rotor |
SYMPTOM CHART
Note. The Wheel speed sensor cable moves in relation to motion of the front or rear suspension. Therefore, it is likely that it has an open circuit only when driving on rough roads but it functions normally when driving on smooth roads. It is recommended to observe sensor output voltage waveform also under special conditions, such as driving on a rough road.
HYDRAULIC UNIT CHECK
Required Special Tools
- MB991958: Scan Tool (MUT-III Sub Assembly) MB991824: Vehicle Communication Interface (V.C.I.) MB991827: MUT-III USB Cable MB991910: MUT-III Main Harness A
| CAUTION | The roller of the braking force tester and the tire should be dry during testing. When testing the front brakes, apply the parking brake. When testing the rear brakes, stop the front wheels with chocks. |
Scheme 90
- Jack up the vehicle. Then support the vehicle with rigid racks at the specified jack-up points or place the front or rear wheels on the rollers of the braking force tester.
- Release the parking brake, and feel the drag force (drag torque) on each road wheel. When using the braking force tester, take a reading of the brake drag force. CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
- Connect scan tool MB991958 to the data link connector.
- After checking that the neutral position < M/T > or the selector lever is in "P" range, start the engine.
- Select "Interactive Diagnosis" from the start-up screen.
- Select "System Select."
- Choose "ABS/TCL" from the "CHASSIS" tab.
- Select "Actuator Test" from "ABS/TCL" screen
- Choose an appropriate item for hydraulic unit check. NOTE: The ABS/TCL system will switch to the scan tool mode and the ABS warning light, TCL indicator and TCL OFF indicator will illuminates. NOTE: When the ABS and TCL has been interrupted by the fail-safe function, scan tool MB991958 actuator testing cannot be used.
- Turn the wheel by hand and check the change in braking force when the brake pedal is depressed. When using the braking force tester, depress the brake pedal until the braking force is at the following values, and check that the braking force changes to the brake drag force reading taken in step 2 when the actuator is force-driven. The result should be as shown in the diagram above. WHEEL SPECIFICATION Front wheel 785 - 981 N (176 - 220 lb) Rear wheel 588 - 784 N (132 - 176 lb)
- If the result of inspection is abnormal, repair according to the Diagnosis Table below. DIAGNOSIS PROCEDURE DIAGNOSIS TABLE MUT-III SCAN TOOL DISPLAY PERATION INSPECTION RESULT JUDGMENT PROBABLE CAUSE REMEDY 01 FR VALVE 02 FL VALVE 03 RR VALVE 04 RL VALVE Depress brake pedal to lock wheel. Using scan tool MB991958, select the wheel to be checked and force the actuator to operate. Turn the selected wheel manually to check the change of brake force. Brake force is released for three seconds after wheels have been locked. Normal - - Wheel does not lock when brake pedal is depressed. Abnormal Clogged brake line other than hydraulic unit Check and clean brake line Clogged hydraulic circuit in hydraulic unit Replace hydraulic unit assembly Brake force is not released Incorrect hydraulic unit brake tube connection Connect correctly Hydraulic unit solenoid valve not functioning correctly Replace hydraulic unit assembly
- After inspection, disconnect scan tool MB991958 immediately after turning the ignition switch to the "LOCK" (OFF) position.
IN THE EVENT OF A DISCHARGED BATTERY
| WARNING | If the ABS is not operating, the vehicle will be unstable during braking, Do not drive the vehicle with the ABS/TCL-ECU connector disconnected or with the ABS/TCL not operating for any other reason. |
If the engine is started using a booster cable when the battery is completely flat, and the vehicle is then driven without waiting for the battery to be recharged, the engine may misfire and it may not be possible to drive the vehicle. This is because the ABS consumes a large amount of current when carrying out its initial checks. If this happens, recharge the battery fully.