P0556
DTC P0556
Circuit Description
The brake booster pressure sensor measures the negative air pressure or vacuum in the brake booster assembly. The engine control module (ECM) supplies the following circuits to the brake booster pressure sensor:
* A 5-volt reference circuit
* A signal circuit
* A low reference circuit
During engine running conditions, the brake booster pressure sensor signal circuit voltage varies, depending on the vacuum reserve internal to the brake booster. If the ECM detects that the brake booster vacuum is less than the intake manifold vacuum, then DTC P0556 sets.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0556 Brake Booster Pressure Sensor Performance
Conditions for Running the DTC
* The engine is running at an idle condition.
* The ignition voltage is greater than 11 volts, but less than 18 volts.
* DTC P0556 runs continuously once the above conditions are met.
Conditions for Setting the DTC
The ECM detects brake booster vacuum as being less than the intake manifold vacuum for more than 100 milliseconds.
Action Taken When the DTC Sets
* The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
* The control module records the operating conditions at the time the diagnostic fails. The control module stores the information in the Freeze Frame/Failure Records.
Conditions for Clearing the MIL/DTC
* The control module turns OFF the MIL after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
* A current DTC, last test failed, clears when the diagnostic runs and passes.
* A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
* Clear the MIL and the DTC with a scan tool.
