DTC P1574 Stoplamp Switch Circuit. Cadillac Concours 1997

For 1990-2009 cars

### Circuit Description

This diagnostic test functions on the assumption that a sudden decrease in non-drive (rear) wheel speed must be caused by a brake application. Non-drive wheel speed and stop lamp switch status are supplied to the PCM through serial data from the Electronic Brake and Traction Control Module (EBTCM). If there is a 2.5 MPH or greater decrease of non-drive wheel speed in 0.4 seconds and a transition of the TCC or extended travel contacts of the TCC brake switch without a transition of the stop lamp brake switch, DTC P1574 is set.

### Conditions for Setting the DTC

#### Test Conditions

• | DTCs P0703, P1575 and P1602 not set.

• | Traction control and antilock brake systems have not failed.

• | Traction control and antilock brake systems are not active.

• | Non-drive wheel speed goes above 20 MPH and then doesnt go below 4 MPH.

#### Failure Condition

A 2.5 MPH or greater decrease in non-drive wheel speed in 0.4 second and extended travel brake switch or TCC brake switch indicating brakes applied and no transition noticed in the stop lamp contacts of the Stop/BTSI/Cruise brake switch.

### Action Taken When the DTC Sets

PCM will set the stop lamp switch status to not applied.

• | The Malfunction Indicator Lamp (MIL) will not illuminate.

• | No message will be displayed.

### Conditions for Clearing the DTC

• | A History DTC will clear after forty consecutive warm-up cycles with no failures of any non-emission related diagnostic test.

• | A Last Test Failed (current) DTC will clear when the diagnostic runs and does not fail.

• | Use a scan tool to clear DTCs.

• | Interrupting PCM battery voltage may or may not clear DTCs. This practice is not recommended. Refer to Clearing Diagnostic Trouble Codes in PCM Description and Operation.

### Diagnostic Aids

DTC P1574 indicates the stop lamp switch signal to the EBTCM or the EBTCMs ability to send the stop lamp switch signal to the PCM has failed. Refer to ABS/TCS DTCs for diagnosis of the stop lamp switch signal and the EBTCM.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | Go to A Powertrain On Board Diagnostic (OBD) System Check
2 | Is DTC P1602 also set? | -- | Go to DTC P1602 Loss of EBTCM Serial Data | Refer to Diagnostic Aids