Circuit Description
This diagnostic test functions on the assumption that a sudden decrease in non-drive 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 (EBCM). If there is a 6 mph or more decrease of non-drive wheel speed in 0.4 seconds and a transition of the TCC contacts at the TCC/Brake switch or stop lamp switch without a transition of the extended travel contacts of the TCC/Brake switch, DTC P1575 is set.
Conditions for Running the DTC
| • | P1574 not set |
| • | The traction control and antilock brake systems have not failed |
| • | The traction control and antilock brake systems are not active. |
| • | The non-drive wheel speed goes above (32 km/h) ( 20 mph) and then does not go below (6 km/h) (4 mph). |
Conditions for Setting the DTC
A 6 mph or more decrease in non-drive wheel speed in 0.4 seconds and the TCC/Brake switch or stop lamp switch indicating brakes applied and no transition is noticed in the extended travel contacts of the TCC/Brake switch indicating brakes applied.
Action Taken When the DTC Sets
| • | The PCM disables cruise control. |
| • | The PCM will set the extended travel brake switch status to not applied. |
| • | The malfunction indicator lamp (MIL) will not illuminate. |
| • | The PCM will command a message to be displayed. |
| • | The PCM may record operating conditions at the time the diagnostic fails. This information will be stored in the Failure Records. |
Conditions for Clearing the Message/DTC
| • | The PCM will turn the message OFF after one run and pass of the diagnostic test. |
| • | A History DTC will clear after forty consecutive warm-up cycles with no failures of any non-emission related diagnostic test. |
| • | Use a scan tool to clear DTCs. |
Diagnostic Aids
This DTC is difficult to set. The most probable cause of setting this DTC is a "panic" stop situation.
If the condition is intermittent, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Cruise Control Schematics | |||
1 | Did you perform A Diagnostic System Check-Cruise Control? | Go to Step 2 | |
2 |
Does the scan tool parameter indicate Released? | Go to Step 3 | Go to Step 4 |
3 |
Does the scan tool parameter indicate Applied? | Go to Diagnostic Aids | Go to Step 7 |
4 |
Does the test lamp illuminate? | Go to Step 10 | Go to Step 5 |
5 |
Does the test lamp illuminate? | Go to Step 6 | Go to Step 8 |
6 | Test the extended travel brake switch signal circuit for a open circuit or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 13 | Go to Step 9 |
7 | Test the extended brake travel signal circuit for a short to voltage. Refer to Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 13 | Go to Step 9 |
8 | Repair the open ignition positive voltage circuit of the TCC/Brake switch. Refer to Wiring Repairs In Wiring Systems. Did you repair the condition? | Go to Step 13 | -- |
9 | Inspect for poor connections at the harness connector of the TCC/Brake switch. Refer to Testing for Intermittent Conditions and Poor Connections and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 13 | Go to Step 11 |
10 | Inspect for poor connections at the harness connector of the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 13 | Go to Step 12 |
11 | Replace the TCC Brake switch. Refer to Stop Lamp Switch Replacement in Hydraulic Brakes. Did you complete the replacement? | Go to Step 13 | -- |
12 |
Important: The PCM must be reprogrammed before replacement. Refer to Powertrain Control Module Programming in Engine Controls. Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls. Did you complete the replacement? | Go to Step 13 | -- |
13 | Operate the system within the Conditions for Running the DTC as specified in the supporting text. Does the DTC reset? | Go to Step 2 | System OK |
