GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2001 🢒 Catera 🢒 Brakes 🢒 Antilock Brake System 🢒 DTC C0161

Circuit Description

The Stoplamp Switch is a normally open switch, when the brake pedal is depressed the EBCM will sense battery voltage. This allows the EBCM to determine the state of the brake lamps.

Conditions for Running the DTC
    • The ignition switch is ON.
    • The DTC can be set after system initialization.

Conditions for Setting the DTC
    • EBCM detects battery voltage at all times.
    • EBCM never detects battery voltage from feed circuit.
    • Both brake lamps are faulty.

Action Taken When the DTC Sets

If equiped, the following actions occur:

    • DTC C0161 is set.
    • ABS and TCS remains active.

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 ignition cycles pass with no DTCs detected.

Diagnostic Aids
    • It is very important that a thorough inspection of the wiring and connectors be performed. Failure to carefully and fully inspect wiring and connectors may result in misdiagnosis, causing part replacement with reappearance of the malfunction.
    • Thoroughly inspect any circuitry that may be causing the 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
    • The following conditions may cause an intermittent malfunction:
       - A poor connection
       - Rubbed-through wire insulation
       - A broken wire inside the insulation
    • If an intermittent malfunction exists refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This DTC detects an open stoplamp switch signal circuit from the stoplamp side of the splice to the EBCM.

    2.

  2. The EBCM sources 5 volts on the stoplamp switch signal circuit. This small voltage has a ground path through the stoplamp bulbs. This DTC sets if the path to ground is open.

    3.

  3. With the scan tool, Test for the current state of the brake lamp switch parameter.

    4.

  4. Test the stoplamp signal circuit for a short to voltage.

Step

Action

Yes

No

Schematic Reference: Antilock Brake System Schematics

1

Did you perform the ABS Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - ABS

2
  1. Press the brake pedal.
  2. With the scan tool, observe the Brake Switch Status parameter in the ABS data list.

Does the Brake Switch Status parameter display Applied?

Go to Step 4

Go to Step 3

3

Test the signal circuit of the stoplamp switch for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 15

Go to Step 11

4

Press the brake pedal.

Are all of the stoplamps OFF?

Go to Step 5

Go to Step 7

5

Test the feed circuit of the stoplamps for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 15

Go to Step 6

6

Test the ground circuit of the stoplamps for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 15

Go to Diagnostic Aids

7

  1. Press the brake pedal.
  2. With a scan tool, observe the Brake Switch Status parameter.

Does the Brake Switch Status parameter change state?

Go to Diagnostic Aids

Go to Step 8

8
  1. Turn OFF the ignition.
  2. Inspect the stoplamp switch and adjust and/or calibrate if needed.

Did you find and correct the condition?

Go to Step 15

Go to Step 9

9
  1. Turn OFF the ignition switch.
  2. Disconnect the stoplamp switch connector.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, observe the Brake Switch Status parameter.

Does the scan tool display Released?

Go to Step 11

Go to Step 10

10

Test the stoplamp signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 15

Go to Step 12

11

Inspect for poor connections at the harness connector of the stoplamp switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 15

Go to Step 13

12

Inspect for poor connections at the harness connector of the EBCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 15

Go to Step 14

13

Replace the stoplamp switch. Refer to Stop Lamp Switch Replacement in Park Brakes.

Did you complete the repair?

Go to Step 15

--

14

Replace the EBCM. Refer to Electronic Brake Control Module Replacement .

Did you complete the replacement?

Go to Step 15

--

15
  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

Go to Step 2

System OK