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 6 mph or greater decrease of non-drive
wheel speed in 0.4 seconds and a transition of the contacts at the TCC
brake switch or stop lamp switch without a transition of the extended
travel contacts of the TCC/antilock brake switch, DTC P1575 is set.
Conditions for Running the DTC
| • | DTCs P0703, P1574 and P1604 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 doesn't
go below 4 mph. |
Conditions for Setting the DTC
A 6 MPH or greater decrease in non-drive wheel speed in 0.4 second
and TCC brake switch or Stop/BTSI/Cruise brake 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
| • | PCM disables cruise control. |
| • | 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. |
| • | A Last Test Failed (current) DTC will clear when the diagnostic
runs and does not fail. |
| • | Use a scan tool to clear DTCs. |
Diagnostic Aids
The operating conditions as well as the state of the extended travel
brake switch circuit will be stored when the DTC was set.
Reviewing the Failure Rec. may help diagnose an intermittent
failure by showing how long ago and under what conditions the DTC set.
