Scan Tool Testing and Procedures

The Tech 1 has five test modes for diagnosing the ABS. The test modes are as follows:
1. Mode F0 - Data List: In this test mode, the Tech 1 continuously monitors wheel speed data and brake switch status.
2. Mode F1 - History Data: In this test mode, fault code history data is displayed. This data includes the number of ignition cycles since the fault code occurred and other information. Up to three fault codes are included in the ABS history data.
3. Mode F2 - Trouble Codes: In this test mode, trouble (fault) codes stored by the EBCM may be displayed or cleared.
4. Mode F3 - ABS Snapshot: In this test mode, the Tech 1 captures and records ABS data before and after a fault occurs.
5. Mode F4 - ABS Tests: In this test mode, the Tech 1 performs hydraulic modulator functional tests to assist in problem isolation during diagnosis.

Mode F0: ABS Data List
The DATA LIST mode allows continuous monitoring of wheel speed data and brake switch status. When monitoring wheel speed data, the signals being sent from the wheel speed sensors to the EBCM are displayed. In this test mode, the vehicle can be driven while wheel speed data is displayed. The readings can be compared with vehicle speed to check for proper operation. Wheel speed signals can also be compared with each other to determine whether they are within specification.
If one wheel speed signal differs greatly from the other signals, improper operation of that sensor may be indicated. Intermittent wheel speed signals can be located in the DATA LIST mode by looking for signals that vary for no reason during vehicle operation.
In the DATA LIST mode, brake switch operation is displayed. With the brake pedal depressed, the Tech 1 screen reads ON, when the pedal is released, the screen reads OFF.

Mode F1: History Data
In the HISTORY DATA test mode, fault code history data is displayed. This data includes the number of ignition cycles since the fault occurred, brake switch status and ABS state when the fault occurred. Up to three codes are included in the ABS history data.

Mode F2: Trouble Codes
In the TROUBLE CODES test mode, ABS trouble (fault) codes stored by the EBCM are displayed. The EBCM can store up to three different codes. The Tech 1 can also clear stored codes when it is used in this test mode.
In addition to storing three trouble codes, the EBCM records when each code was set and ABS status when each code was set. Each code is accompanied by a brief description of what the code number represents.
After displaying the codes, the Tech 1 can be ordered to clear the codes. It will respond to the clear codes command by displaying one of the following screens:
1. ABS CODES CLEARED.
2. CODE CLEAR FAIL.

In addition to storing fault codes, the EBCM stores other information about the codes that may aid in diagnosis. This function is called ENHANCED DIAGNOSTIC DATA. The Tech 1 can be ordered to display the following ENHANCED DIAGNOSTIC DATA:
1. Brake Light Switch Status: Indicates whether the brake light switch was On or Off when the code set.
2. ABS State: Indicates whether or not the anti-lock mode was engaged when the code set.
3. Vehicle Speed: Indicates vehicle speed when the code set.
4. Ignition Cycles: Indicates how many ignition cycles have occurred since the code set.

Mode F3: ABS Snapshot
The ABS SNAPSHOT mode mode will help isolate intermittent problems by capturing data before and after a trigger condition. This data can then be analyzed to determine the cause of the complaint. Three different trigger conditions can activate the ABS SNAPSHOT mode:
1. Automatic Trigger: When the snapshot mode is used with the automatic trigger, the Tech 1 captures data which deviates from normal operation without setting a code.
2. ABS Code Set Trigger: Snapshot data can be captured by specifying an ABS code. When the Tech 1 is used with the code set trigger, it captures data immediately before and after the code setting.
3. Snapshot On Command: Snapshot data can be captured on command by pressing the Tech 1 ENTER key. When used with the command trigger, the Tech 1 continuously monitors data and waits for the ENTER command to begin storing data.

The snapshot can be set to capture data at the beginning, center or end of the data stream. Approximately 15 seconds of data are captured before the Tech 1 data buffer is full. If ``Beginning'' is selected, data occurring approximately 15 seconds before and up to the trigger point is captured. If ``Center'' is selected, data occurring approximately 8 seconds before through 8 seconds after the trigger point is captured. If ``End'' is selected, data occurring approximately 15 seconds after the trigger point is captured.

Mode F4: ABS Tests
The ABS TESTS mode performs functional tests on the ABS which help verify proper operation. In this mode, error conditions can be further identified by testing and observing the test results. In the ABS TESTS mode the following tests can be performed:
1. Solenoid Valve-Pressure Reduction: This test indicates whether specific solenoid valves in the hydraulic modulator release pressure to assigned wheel circuits.
2. Solenoid Valve-Pressure Hold: This test indicates whether specific solenoid valves in the hydraulic modulator hold pressure in assigned wheel circuits.
3. Static ``BITE'' Test: This test cycles each solenoid valve operates the pump motor briefly. The EBCM will store a fault code if the test conditions fail.

The PRESSURE REDUCE test activates a selected hydraulic wheel circuit valve, placing it in the pressure reduce position. Valve action can then be verified by checking the appropriate wheel for proper brake action. The Tech 1 will indicate whether the valve action was commanded properly. This test is used in conjunction with the PRESSURE HOLD test to completely check each solenoid valve. With an assistant, the pressure reduce test can be verified as follows:
1. Have an assistant apply the brakes.
2. Use Tech 1 to command the PRESSURE REDUCE mode.
3. Try to spin wheel being tested. It should spin due to the reduce command.

The PRESSURE HOLD test activates a selected hydraulic wheel circuit valve, placing it in the pressure hold position. Valve action can then be verified by checking the appropriate wheel for proper brake action. The Tech 1 will indicate whether the valve action was commanded properly. This test is used in conjunction with the PRESSURE REDUCE test to completely check each solenoid valve. With an assistant, the pressure reduce test can be verified as follows:
1. Spin wheel freely.
2. Use Tech 1 to command the PRESSURE HOLD mode.
3. Have an assistant apply the brakes.
4. Try to spin wheel being tested. It should spin due to the hold command, even if the brakes are applied.

The STATIC ``BITE'' test is performed automatically by the EBCM once during each ignition cycle when the vehicle speed reaches 3-11 mph. The Tech 1 will perform this test automatically the ABS TESTS mode. The BITE test cycles each solenoid valve and the pump motor to check component operation. If any error is detected during this test, the EBCM will set a code.