P105

Circuit Description

The brake booster vacuum sensor changes resistance based on the vacuum inside the brake booster. This diagnostic test monitors the brake booster vacuum along with the manifold vacuum. If the brake booster vacuum is too low for a given manifold vacuum and the brakes are not applied, then the brake booster vacuum signal must be in error and Code P105 is set.

Test Condition(s)

1. Codes P031, P032, P034, P071 and P137 not set.
2. RPM 500 or greater for 20 seconds.
3. Brakes not applied.
4. Barometric pressure 72 kPa or greater.
5. MAP 60 kPa or less.

Failure Condition(s)

Brake booster vacuum 5 kpa vacuum or less for 16 seconds.

Action Taken

1. PCM turns 'ON' the 'SERVICE VEHICLE SOON' message.

Notes on Fault Tree

1. Diagnose Code P103 first because it can cause other BBV problems.
2. If the brake booster vacuum signal is too low, PD84 will be 5 kPa or less. If it is not, then the signal is not too low.
3. Checking for vacuum leaks that are causing the low signal.
4. With the BBV sensor pins 'B' and 'C' jumpered together, PD84 should read greater than 81 kPa. If it does not check CKT 1726 for a short to ground.
5. If resistance measures less than 500 ohms check circuit for a short to ground.
6. If resistance measures less than 10K ohms check circuit for a short to ground.