DTC C1291 Open Brake Lamp Switch Contacts During Deceleration w/NW9
Circuit Description
The EBCM uses this stoplamp switch circuit for various performance measures within DRP/ABS/TCS/VSES. The EBCM detects an open circuit in non-ABS braking. This DTC sets when the EBCM does not detect closure of the brake switch while the car is decelerating at level that indicates the brakes are applied. Several deceleration events without detection of a closed brake switch are required before this DTC is set.
Conditions for Running the DTC
The ABS conditions and the braking conditions are normal.
Conditions for Setting the DTC
The stoplamp switch remains open for 3 deceleration cycles.
Action Taken When the DTC Sets
| • | The EBCM disables the TCS for the duration of the ignition cycle. |
| • | The TRAC OFF indicator turns ON. |
| • | The ABS remains functional. |
Conditions for Clearing the DTC
| • | The condition for the DTC is no longer present and the DTC is cleared with a scan tool. |
| • | The electronic brake control module (EBCM) automatically clears the history DTC when a current DTC is not detected in 100 consecutive drive cycles. |
Diagnostic Aids
| • | Diagnose any wheel speed sensor DTCs before continuing with the diagnosis of the DTC. |
| • | A deceleration cycle consists of the following sequence: |
| 1. | The vehicle speed is greater than 24 km/h (15 mph). |
| 2. | The vehicle decelerates more than 8 km/h/second (5 mph/second) for 2 seconds. |
| 3. | The vehicle speed decelerates to less than 16 km/h (10 mph). |
| • | Verify proper stop lamp switch operation using the data list of the scan tool. As the brake is applied, the data list displays the stop lamp switch on within 2.54 cm (1 in) of travel. |
| • | Possible causes of this DTC are the following conditions: |
| - | An open stop lamp switch |
| - | The stop lamp switch is misadjusted |
| - | An open fuse |
| - | Circuit has a wiring problem, terminal corrosion, or poor connections |
| - | Erratic wheel speeds |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
Tests the circuit for a change in states.
-
Tests for proper operation of the circuit by bypassing the stoplamp/auto trans shift lock control switch. If the fuse in the jumper opens when you perform this test, the signal circuit of the stoplamp/auto trans shift lock control switch is shorted to ground.
Step | Action | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the ABS Diagnostic System Check? | -- | Go to Step 2 | |||||||
2 | Press the brake pedal. Do the brake lamps turn ON? | -- | Go to Step 3 | Go to Step 7 | ||||||
Does the Brake Switch - ABS Input parameter change state? | -- | Go to Diagnostic Aids | Go to Step 4 | |||||||
4 |
Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 5 | ||||||
Does the scan tool display Applied? | -- | Go to Step 11 | Go to Step 6 | |||||||
6 | Test the signal circuit of the stoplamp/auto trans shift lock control switch for an open between the splice pack of the stoplamp signal circuit and the EBCM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 10 | ||||||
7 | Test the battery feed circuit of the stoplamp/auto trans shift lock control switch for a short to ground or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 8 | ||||||
8 | Test the signal circuit of the stoplamp/auto trans shift lock control switch for an open between the stoplamp/auto trans shift lock control switch and the splice of the stoplamp signal circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 9 | ||||||
9 | Test the signal circuit of the stoplamp/auto trans shift lock control switch for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 10 | ||||||
10 | 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 14 | Go to Step 12 | ||||||
11 | Inspect for poor connections at the harness connector of the stoplamp/auto trans shift lock control 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 14 | Go to Step 13 | ||||||
12 |
Important: Perform the setup procedure for the EBCM. An unprogrammed EBCM will
result in the following conditions:
Replace the EBCM. Refer to Electronic Brake Control Module Replacement . Did you complete the replacement? | -- | Go to Step 14 | -- | ||||||
13 | Replace the stoplamp/auto trans shift lock control switch. Refer to Stop Lamp Switch Replacement in Hydraulic Brakes. Did you complete the replacement? | -- | Go to Step 14 | -- | ||||||
14 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
