Circuit Description
This DTC is used in order to identify open stoplamp switch circuitry that prevents the stoplamp switch input from changing states when the brake is applied. This DTC is used in conjunction with DTC C1291 in order to determine the cause of an open stoplamp switch malfunction.
Conditions for Running the DTC
The ignition is ON.
Conditions for Setting the DTC
The stoplamp switch input voltage is between 3.4 volts and 5.3 volts for 2 seconds.
Action Taken When the DTC Sets
| • | The EBCM disables the TCS for the duration of the ignition cycle. |
| • | The TRACTION CONTROL indicator turns ON. |
| • | The ABS remains functional. |
Conditions for Clearing the DTC
| • | The condition for the DTC is no longer present (the DTC is not current) and you used the scan tool Clear DTC function. |
| • | The condition for the DTC is no longer present (the DTC is not current) and you used the On-Board Diagnostics Clear DTC function. |
| • | The EBCM automatically clears the history DTC when a current DTC is not detected in 50 consecutive drive cycles. |
Diagnostic Aids
Possible causes of this DTC are the following conditions:
| • | A signal circuit of the stop lamp switch is open. |
| • | The stop lamp switch is misadjusted. |
| • | 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. |
| • | All brake lamps are open. |
| • | All brake lamp grounds are open. |
| • | Circuit has a wiring problem, terminal corrosion, or poor connections. |
| • | Loose or corroded EBCM ground or ECM ground. |
| • | An internal EBCM problem. |
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/AT shift lock control switch. If the fuse in the jumper opens when you perform this test, the signal circuit of the stoplamp/AT 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 Light Switch 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/AT shift lock control switch for an open between the EBCM and the splice of the stoplamp switch 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 10 |
7 | Test the battery feed circuit of the stoplamp/AT 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/AT shift lock control switch for an open between the stoplamp/AT shift lock control switch and the splice of the stoplamp switch 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/AT 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/AT 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 | Replace the EBCM. Refer to Electronic Brake Control Module Replacement . Did you complete the replacement? | -- | Go to Step 14 | -- |
13 | Replace the stoplamp/AT 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 |
