P1576

CIRCUIT DESCRIPTION

The Brake Booster Vacuum (BBV) sensor changes resistance based on the vacuum inside the brake booster. This diagnostic test checks for a vacuum sensor reading which would be caused by a shorted sensor or a short on CKT 1809 or an open on CKT 808, i.e. signal voltage 5 volts (82 kPa VAC) or greater. Every time the TCC brake switch cycles from closed to open with the engine not at idle, this test checks for a shorted vacuum signal. Since 82 kPa could occur normally under certain conditions this test will not fail unless five consecutive cycles of the TCC brake switch with 82 kPa is monitored. Any cycle of the TCC brake switch where a shorted vacuum signal is not detected will reset the counter to zero.

CONDITIONS FOR SETTING THE DTC

Test Conditions

^ DTCs P0107, P0108, P0703, and P1106 not set.
^ Extended travel brake switch open for at least one second.
^ MAP value was 30 kPa or greater for the second the extended travel brake switch was open.

Failure Condition

Brake booster vacuum was 82 kPa or greater for five consecutive occurrences of the above test conditions.

ACTION TAKEN WHEN THE DTC SETS

^ 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.
^ PCM battery voltage is interrupted.
^ Using a Scan tool.

DIAGNOSTIC AIDS

Manipulate the wire harness while watching the scan tool display looking for opens and shorts.

Reviewing the Failure Rec. may help diagnose an intermittent failure by showing how long ago and under what conditions the DTC set.

TEST DESCRIPTION

Number(s) below refer to the step number(s) on the Diagnostic Table.

2. BBV display will read 82 kPa to 84 kPa with the sensor shorted. If it does not, fault is not present.