DTC C1291 Open Brake Lamp Switch Contacts During Deceleration. Buick Regal 1998

For 1990-2009 cars only

Makes 🢒 Buick 🢒 1998 🢒 Regal 🢒 DTC 🢒 DTC C1291 Open Brake Lamp Switch Contacts During Deceleration

ABS Components
Antilock Brake System Schematics
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice
Power Distribution Schematics

Circuit Description

DTC C1291 detects an open brake switch in the non-ABS mode. The EBCM/EBTCM looks for deceleration rates that may indicate braking action. The EBCM/EBTCM verifies braking action by repeating the method for finding deceleration rates that indicate braking action several times. In each case, the ABS will not be available because the EBCM/EBTCM does not see the brake switch input.

Conditions for Setting the DTC

DTC C1291 can set if three deceleration cycles within the specified rate occur during the current ignition cycle with the brake switch off.

Action Taken When the DTC Sets

•	A malfunction DTC stores.

•	The ABS/ETS/TCS disables.

•	The amber ABS/ETS/TCS warning indicator(s) turns on.

Conditions for Clearing the DTC

•	The condition responsible for setting the DTC no longer exists and the Scan Tool Clear DTCs function is used.

•	100 drive cycles pass with no DTC(s) detected.

Diagnostic Aids

The following conditions may cause an intermittent malfunction:

•	A poor connection

•	Rubbed-through wire insulation

•	A broken wire inside the insulation

Use the enhanced diagnostic function of the Scan Tool in order to measure the frequency of the malfunction. Refer to the Scan Tool manual for the procedure.

Thoroughly inspect any circuitry that may cause the intermittent complaint for the following conditions:

•	Backed out terminals

•	Improper mating

•	Broken locks

•	Improperly formed or damaged terminals

•	Poor terminal-to-wiring connections

•	Physical damage to the wiring harness

Important: Zero the J 39200 test leads before making any resistance measurements. Refer to the J 39200 user's manual.

Step

Action

Value(s)

Yes

Was the Diagnostic System Check performed?

Go to Step 2

Go to Diagnostic System Check

Turn the ignition switch to the RUN position.

Do not start the engine.

Install a Scan Tool .
Use the Scan Tool in order to inspect for DTCs.

Is DTC C1295 set as either a current and/or history DTC?

Go to DTC C1295 Brake Lamp Switch Circuit Open

Go to Step 3

Select Data List on the Scan Tool .
Select Brake Switch Position on the Scan Tool .
Apply light pressure to the brake pedal while monitoring the Brake Switch Position on the Scan Tool.

Does the Scan Tool indicate that the brake switch is on within 25 mm (1.0 inch) of brake pedal travel?

Go to Step 25

Go to Step 4

Apply firm pressure to the brake pedal.
Observe the rear brake lamps.

Are the rear brake lamps on?

Go to Step 5

Go to Step 8

Turn the ignition switch to the OFF position.
Disconnect the 24-way EBCM/EBTCM connector C1.
Turn the ignition switch to the RUN position.

Do not start the engine.

Apply firm pressure to the brake pedal.
Use the J 39200 in order to measure the voltage between the 24-way EBCM/EBTCM harness connector C1 terminal B9 and ground.

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

10.0 V

Go to Step 6

Go to Step 16

Inspect the 24-way EBCM/EBTCM connector C1 and the 24-way EBCM/EBTCM harness connector C1 for the following conditions:

•	Terminal damage

•	Poor terminal contact

•	Terminal corrosion

Is there poor terminal contact, terminal corrosion, or damaged terminals?

Go to Step 17

Go to Step 7

Reconnect the 24-way EBCM/EBTCM connector C1.
Test drive the vehicle and perform a brake stop from 32 km/h (20 mph) while engaging the ABS.
Use the Scan Tool in order to inspect for DTCs.

Does DTC C1291 or DTC C1292 set as a current DTC?

Go to Step 23

Go to Step 25

Use the J 39200 in order to measure the voltage between the stoplamp switch harness connector C1 terminal A and ground.

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

10.0 V

Go to Step 9

Go to Step 11

Insure that the stoplamp switch connector is connected.
Apply firm pressure to the brake pedal.
Use the J 39200 in order to measure the voltage between the stoplamp switch harness connector C1 terminal B and ground.

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

10.0 V

Go to Step 16

Go to Step 10

Inspect for proper adjustment of the stoplamp switch.

Is the stoplamp switch adjusted correctly?

Go to Step 18

Go to Step 19

Remove the fuse block STOPLAMP Fuse (15A).
Use the J 39200 in order to measure the resistance between the STOPLAMP Fuse (15A) terminals.

Is the resistance within the specified range?

0.0-2.0 ohms

Go to Step 12

Go to Step 13

Disconnect the stoplamp switch connector C1.
Use a J 39200 in order to measure the resistance between the stoplamp switch harness connector C1 terminal A and the fuse block terminal F6.

Is the resistance within the specified range?

0.0-2.0 ohms

Go to Step 14

Go to Step 21

Disconnect the 24-way EBCM/EBTCM connector C1.
Use the J 39200 in order to measure the resistance between the 24-way EBCM/EBTCM connector C1 terminal B9 and ground.

Is the resistance within the specified range?

(Infinite)

Go to Step 15

Go to Step 20

Use the J 39200 in order to measure the voltage between the fuse block terminal F5 and ground.

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

10 V

Go to Step 25

Go to Power Distribution Schematics in Wiring Systems

Disconnect the stoplamp switch connector C1.
Use the J 39200 in order to measure the resistance between the stoplamp switch harness connector C1 terminal A and ground.

Is the resistance within the specified range?

(Infinite)

Go to Step 24

Go to Step 22

Repair the open in CKT 17.

Is the repair complete?

Go to Diagnostic System Check

Replace all the terminal or the connectors that exhibit the following conditions: