P1577

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 an open sensor or an open in CKT 474 or a short to ground on CKT 1728, i.e. signal voltage of 0.2 volt (-8 kPa VAC) or less. When the PCM detects a brake booster vacuum signal that is too low, DTC P1577 will set.

CONDITIONS FOR SETTING THE DTC

Test Condition

Test continuously.

Failure Condition

Brake booster vacuum reading 8 kPa vacuum or less for 2 seconds.

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. If the brake booster vacuum sensor is open BBV display should read -8 kPa or less. If it does not, then the fault is not present.
3. If the brake booster vacuum sensor is open BBV display should read 82-84 kPa with terminals C and B jumpered together.