P103

Circuit Description

The brake booster vacuum 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 1726 (i.e. sensor voltage of 0.3 volts (-8 kPa VAC) or less). When the PCM detects a brake booster vacuum signal that is too low, Code P103 will set.

Test Condition(s)

Test continuously.

Failure Condition(s)

Brake booster vacuum reading of 0.2 volt (-8 kPa) or less for 2 seconds.

Action Taken

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

Notes on Fault Tree

1. If the brake booster vacuum sensor is open PD84 should read -8 kpa or less. If it does not, then the sensor is not open.
2. If the brake booster vacuum sensor is open PD84 should read 82-84 kPa with pins 'A' and 'B' jumpered together.
3. Checking CKT 1726 for a short to ground between BBV and PCM.
4. Checking CKT 1726 for an open between BBV and PCM.