P0557
DTC P0557
Circuit Description
The brake booster pressure sensor measures the negative air pressure or vacuum reserve 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 pressure sensor signal circuit is at a low voltage, then DTC P0557 sets.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0557 Brake Booster Pressure Sensor Circuit Low Voltage
Conditions for Running the DTC
* The ignition is ON.
* The ignition voltage is greater than 11 volts, but less than 18 volts.
* DTC P0557 runs continuously once the above conditions are met.
Conditions for Setting the DTC
The ECM detects less than 0.04 volts on the brake booster sensor signal circuit for more than 12.5 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.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
7. This step is measuring the current flow of the 5-volt reference circuit from the ECM.
Step 1 - Step 7:
Step 8 - Step 13:
