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P1577

BBV Sensor Circuit Low Voltage.

  • Chrysler
  • Powertrain
  • Manufacturer code
  • Medium severity

How this code is built

P
SystemPowertrain
1
Defined byThe manufacturer
5
AreaVehicle speed, idle control and auxiliary inputs
77
FaultThe specific fault in that area

What it means

P1577 on a Chrysler is logged as BBV Sensor Circuit Low Voltage. BBV normally stands for brake booster vacuum, so the control unit has seen the sensor's signal voltage fall below the expected range, which points to a short to ground, an open reference supply or a faulty sensor. Exact sensor location, wiring and set conditions vary by model and engine, so check the manufacturer data for the vehicle.

Symptoms

  • Warning lamp on (engine management and possibly brake or stability warning lamps, depending on model)
  • Hard or inconsistent brake pedal feel if booster vacuum is genuinely low
  • Hissing from the booster or vacuum hose area
  • Rough idle or erratic idle if there is a vacuum leak
  • Reduced engine performance or a limited operating mode on some models

Possible causes

  • Faulty brake booster vacuum sensorlikely
  • Damaged, corroded or loose sensor connector or terminalslikely
  • Signal wire shorted to ground or chafed wiringpossible
  • Open circuit or low voltage on the sensor reference supply or a poor sensor groundpossible
  • Genuine low vacuum from a leaking or split vacuum hose, faulty non-return valve or failing boosterpossible
  • Fault inside the control unitrare

How to diagnose

  1. Read all stored and pending codes and note the freeze frame data, looking for related sensor reference or brake system codes.
  2. Check the brake pedal feel with the engine off and then running, and listen for vacuum hissing at the booster.
  3. Inspect the sensor, its connector and the wiring for damage, water ingress, corrosion, chafing and pushed-out terminals.
  4. Inspect the vacuum hose and non-return valve between the engine and the booster for splits, loose fittings and blockage.
  5. View the live sensor reading and compare it with a vacuum gauge at the booster, to separate a real vacuum problem from a sensor or circuit fault.
  6. With the connector unplugged, check the reference voltage, ground and signal wire for shorts and continuity, following the manufacturer wiring diagram.
  7. If the wiring tests are good, test or substitute the sensor as per manufacturer procedure and then confirm the fault does not return.
  8. Check for any software update or technical bulletin for the model, as the procedure varies with engine and year.

How to fix

  • Replace the brake booster vacuum sensor if it fails the tests.
  • Repair or replace damaged wiring, terminals or the connector, and clean up any corrosion.
  • Restore the reference supply or ground connection if the circuit has an open or high resistance.
  • Replace split hoses or a faulty non-return valve to restore proper booster vacuum.
  • Repair or replace the booster if it is leaking internally.
  • Update the control unit software only if the manufacturer lists an outdated calibration as a known cause for this code.

Can I keep driving?

Medium severity

The car can usually be driven short distances to a workshop, but get it checked soon. If the brake pedal feels hard or brake assistance seems reduced, stop driving until it has been inspected.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.

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