For 1990-2009 cars
ABS Components
Antilock Brake System Schematics

### Circuit Description

The brake lamp switch circuit is an input to the EBTCM. It is used to monitor the status of the brake lamp switch. This is important because ABS is activated and TCS is inhibited when the brake switch is on and ABS is inhibited when the brake switch is off.

### Conditions for Setting the DTC

• | There is an open in the brake lamp switch circuit.

• | Both the left and the right brake lamp bulbs are open.

• | There is a misadjusted or a malfunctioning brake lamp switch.

• | There is a malfunction in the EBTCM.

### Action Taken When the DTC Sets

• | A malfunction DTC is stored.

• | The ABS and the TC indicator lamps are turned on.

• | The ABS and the TCS are disabled.

### Conditions for Clearing the DTC

• | The condition for the DTC is no longer present.

• | The scan tool Clear DTCs function is used.

• | 100 drive cycles have passed with no DTCs detected.

### Diagnostic Aids

Perform a thorough inspection of the wiring. Perform a thorough inspection of the connectors. Failure to carefully and fully inspect the wiring and the connectors may result in misdiagnosis. Misdiagnosis causes part replacement with reappearance of the malfunction.

### Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

1. If the brake lamps operate properly, the integrity of the circuit up to splice S206 is verified.

2. This step verifies if the brake switch input is being received by the EBTCM.

3. If both brake lamp bulbs are not open, the malfunction is between splice S206 and the clamp cruise fuse 15, or is an open fuse.

#### DTC 37 - Brake Switch Circuit Malfunction

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Diagnostic System Check performed? | -- | Go to Step 2 | Go to A Diagnostic System Check
2 | Have an assistant observe the rear brake lamps while applying pressure to the brake pedal. Are the brake lamps on? | -- | Go to Step 3 | Go to Step 4
3 |

1. Turn the ignition switch to the OFF position.
2. Install a scan tool.
3. Turn the ignition switch to the RUN position with the engine off.
4. Use the scan tool to select Data List.
5. Apply light pressure to the brake pedal while monitoring the Brake Lamp Switch position on the scan tool.

Does the scan tool indicate the brake lamp switch applied within 25.5 mm (1 in) of travel?

--

Go to Step 6

Go to Step 5

4 |

1. Remove the left brake lamp bulb.
2. Inspect the left brake lamp bulb.
3. Remove the right brake lamp bulb.
4. Inspect the right brake lamp bulb.

Is the left brake lamp bulb and the right brake lamp bulb open?

--

Go to Step 14

Go to Step 8

5 |

1. Turn the ignition switch to the OFF position.
2. Disconnect the 25-pin EBTCM harness connector from the EBTCM.
3. Install the J 39700 Universal Breakout Box with the J 39700-250 Cable Adapter to the EBTCM harness only.
4. While applying firm pressure on the brake pedal use a J 39200 DMM to measure the voltage between the J 39700 terminal 2 and ground.

Is the voltage equal to or greater than the specified voltage?

10 V

Go to Step 6

Go to Step 15

6 |

1. Inspect the 25 pin EBTCM connector terminal 2 for the following:

• | Inspect for damage.

• | Inspect for poor terminal contact.

• | Inspect for corrosion.

2. Check that the 4-pin EBTCM connector is properly retained when connected.

Are the following signs evident:

• | Is poor terminal contact evident?

• | Is corrosion evident?

• | Is damaged terminals evident?

--

Go to Step 16

Go to Step 7

7 |

1. Reconnect all the connectors.
2. Disconnect the scan tool if the scan tool is connected.
3. Test drive the vehicle above 6 km/h (3.5 mph).
4. Apply light pressure to the brake pedal for 3 seconds.

Did DTC 37 reset?

--

Go to Step 13

Go to A Diagnostic System Check

8 | Use a J 39200 DMM to measure the voltage between the brake lamp switch terminal 1 and ground. Is the voltage equal to or greater than the specified voltage? | 10 V | Go to Step 9 | Go to Step 10
9 | While applying firm pressure on the brake pedal use a J 39200 DMM to measure the voltage between the brake lamp switch terminal 2 and ground. Is the voltage equal to or greater than the specified voltage? | 10 V | Go to Step 12 | Go to Step 11
10 | Repair an open in the circuit between 20 A HAZARD fuse 12 and the brake lamp switch. Refer to Wiring Repairs in Wiring Systems. Replace the 20 A fuse 12 if fuse is open. Is the repair complete? | -- | Go to A Diagnostic System Check | --
11 | The brake lamp switch is misadjusted or has open contacts. Readjust or replace the brake lamp switch as necessary. Refer to Stoplamp Switch Replacement in Hydraulic Brakes. Is the repair complete? | -- | Go to A Diagnostic System Check | --
12 | Repair an open in the circuit between the brake lamp switch and the EBTCM. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to A Diagnostic System Check | --
13 | Replace the EBTCM. Refer to EBTCM Replacement . Is the repair complete? | -- | Go to A Diagnostic System Check | --
14 | Replace both of the brake lamp bulbs. Refer to Tail Lamp Bulb Replacement in Lighting Systems. Is the repair complete? | -- | Go to A Diagnostic System Check | --
15 | Repair an open between splice S206 and the EBTCM. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to A Diagnostic System Check | --
16 | Replace all the terminals or replace the connector that exhibits the following signs:

• | That exhibits signs of poor terminal contact.

• | That exhibits signs of corrosion.

• | That exhibits signs of damaged terminals.

Refer to Connector Repairs or Repairing Connector Terminals in Wiring Systems.

Is the repair complete?

--

Go to A Diagnostic System Check

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