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 could be caused by an open sensor or an open or shorted 5 volt reference or BBV input circuit. When the PCM detects a brake booster vacuum signal voltage of 0.2 volt (-8 kPa VAC) or less, 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. |
| • | 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
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.
-
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.
-
If the brake booster vacuum sensor is open BBV display should read 82-84 kPa with terminals C and B jumpered together.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to A Powertrain On Board Diagnostic (OBD) System Check | |
Is the display the same or more than the value specified? | -7 kPa | Fault not present. Refer to Diagnostic Aids | ||
Is the display the same or more than the value specified? | -7 kPa | |||
4 |
Is the voltage the same or more than the value specified? | 4.5 volts | ||
5 |
Is the resistance the same or less than the value specified? | 100 ohms | ||
6 | Measure the resistance between PCM connector C1 terminal 70 and BBV sensor connector terminal B (harness side). Is the resistance the same or less than the value specified? | 5 ohms | ||
7 |
Is the resistance the same or less than the value specified? | 100 ohms | ||
8 | Measure the resistance between PCM connector C1 terminal 65 and BBV sensor connector terminal C (harness side). Is the resistance the same or less than the value specified? | 5 ohms | ||
9 | Repair open in CKT 605. Is the repair complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | -- |
10 | Repair short in CKT 605. Is the repair complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | -- |
11 | Repair open in CKT 1809. Is the repair complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | -- |
12 | Repair short to ground in CKT 1809. Is the repair complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | -- |
13 |
Was terminal contact repaired? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | |
14 | Replace the BBV sensor. Is the replacement complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | -- |
15 |
Was terminal contact repaired? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | |
16 | Replace the PCM. Refer to PCM Replacement/Programming . Is the replacement complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | -- |
