GM Service Manual Online
For 1990-2009 cars only

TBCM Scan Tool Data List

Scan Tool Parameter

System State

Expected Value

Definition

Operating Conditions: Ignition is ON, engine OFF, and vehicle is stationary

ABS Active

--

No

The scan tool displays Yes/No. The scan tool displays No when ABS is not active.

Brake Apply Pressure Status

--

Valid

The scan tool displays Invalid or Valid. The scan tool displays Valid when the ignition is ON, and the brake apply sensor is not faulted.

Battery Voltage Signal

--

Varies

The scan tool displays 0-18 Volts. The scan tool displays approximately 12 Volts when the ignition is ON.

Brake Switch Status

--

Off

The scan tool displays On/Off. The scan tool indicates Off when the brake is not applied.

Electric Trailer Brakes Detected

--

No

The scan tool displays Yes or No. The scan tool displays Yes when the vehicle is connected to a trailer equipped with electric brakes.

HS Communication

--

Yes

The scan tool displays Yes or No.

Ignition Run/Crank

--

Inactive

The scan tool will display Active or Inactive. The scan tool will display Active when the signal received from the ECM Run/Crank position.

Master Cylinder Pressure Sensor Input

--

Varies

The scan tool will display brake fluid pressure. The scan tool will display kPa or psi signal received from the TBCM.

Manual Apply Switch

--

Varies

The scan tool displays percent of manual apply lever travel. The scan tool displays 0-100%.

Manual Apply Switch

--

Varies

The scan tool displays percent of manual apply lever travel. The scan tool displays 0-100%.

Manual Apply Switch

--

Varies

The scan tool displays Volts. This is the voltage of the manual apply lever.

Manual Apply Switch Position Error

--

Varies

The scan tool displays percent of error between the manual apply and redundant manual apply signals. The scan tool displays 0-100%. A proper functioning switch should have a value less than 20 %

Redundant Manual Apply SW.

--

Varies

The scan tool displays percent of manual apply lever travel using a redundant signal track. The scan tool displays 0-100%

Redundant Manual Apply SW.

--

Varies

The scan tool displays volts. This is the voltage of the manual apply switch.

Trailer Brake Control

--

Enabled

The scan tool will display Engage/Disengage. The scan tool will display the signal received from the TBCM.

TBCM Diagnostic Fault

--

No

The scan tool will display Yes or No if a fault is detected. The scan tool will display the Yes if a fault signal is received from the TBCM.

TBCM Relay Feedback

--

Varies

The scan tool displays a numeric value.

TBCM Relay Feedback Signal

--

12 Volts

The scan tool displays percent of PWM. The scan tool displays 0-100%.

Trailer Stop Lamp Signal

--

Not Requested

The scan tool will display Not Requested or Requested depending on the state of the brake switch, and manual apply lever. Requested will be displayed if the brake switch is active or the manual apply lever is applied.

TBCM Cmd. Duty Cycle

--

Varies

The scan tool displays percent of battery voltage output commanded to the trailer brakes and depends on battery voltage and user gain setting. Approximately 100% will be indicated when user gain is set to 10.0 and the manual apply lever is fully applied with the engine running.

Trailer Brake Relay Cmd.

--

12 Volts

The scan tool displays 0-18 Volts. The scan tool displays voltage commanded to the trailer brakes when a trailer with electric brakes is connected and depends on battery voltage and user gain setting. Approximately 12-14 volts will be indicated when user gain is set to 10.0 and the manual apply lever is fully applied with the engine running.

Trailer Brake Relay Status

--

Enabled

The scan tool will display Disabled or Enabled. Enabled will be displayed whenever there are no faults present in the TBCM system.

Trailer Connection Detected

--

No

The scan tool displays Yes or No. The scan tool displays Yes when a trailer with electric trailer brakes is connected.

Trailer Disconnect Detected

--

No

The scan tool will display Yes or No depending on the trailer connections. Yes will be displayed if a trailer connection is made to a trailer equipped with electric trailer brakes, and a disconnect occurs within the same ignition cycle.

User Gain Switch

--

Varies

The scan tool displays percent of full gain setting. The scan tool displays 0-100%. Each full gain setting represents an increment of approximately 10 percent of full gain setting. Approximately 40% will be indicated with a gain setting of 4.0, 65% will be indicated with a gain setting of 6.5, etc.

User Gain Switch

--

Varies

The scan tool displays percent of full gain setting. The scan tool displays 0-100%. Each full gain setting represents an increment of approximately 10 percent of full gain setting. Approximately 40% will be indicated with a gain setting of 4.0, 65% will be indicated with a gain setting of 6.5, etc.

User Gain Switch

--

Varies

The scan tool displays volts. This is the voltage of the full gain setting.

Vehicle Speed

--

km/h or mph

The scan tool displays 0-327 km/h (0-204 mph). The scan tool displays 0 km/h (0 mph) when the vehicle is not moving or is moving at speeds less than or equal to 0 km/h (0 mph).