Turbocharger Wastegate Solenoid B Malfunction
The PCM has detected an abnormal reading in the turbocharger wastegate solenoid “B” circuit. Circuit B represents a particular wastegate solenoid (where multiple solenoids are used in sequence). There is no set rule for positioning of wastegate solenoids. Check manufacturer’s specifications for specific solenoid locations.
Code Set Parameters
Sensor input voltage signals (received by the PCM) that indicate a solenoid voltage level that is less or greater than what is specified by the manufacturer will cause a code to be stored and a malfunction indicator lamp to be illuminated. The PCM recognizes this data as an inability to effectively control wastegate operation.
Symptoms may include reduced engine acceleration, whining or rattling noises from the turbocharger or turbo pipes, abnormal smoke from the exhaust, spark plug fouling, excessive engine or transmission temperature, hissing noises from the turbocharger wastegate and/or hoses, and an overall lack of engine performance. Additional codes may include other turbocharger codes, engine misfire codes, or knock sensor codes. Cylinder detonation is another possibility, due to high engine temperatures experienced when boost pressure is excessive. The boost pressure gauge (if so equipped) will exhibit abnormally high levels of boost pressure.
The most common causes of this code include a faulty wastegate solenoid, shorted or open wiring in the wastegate solenoid circuit, loose, corroded, or disconnected electrical connectors in the wastegate solenoid.
Wastegate solenoid replacement should be performed only after making sure that the wastegate linkage and door are functioning properly. Failure to thoroughly diagnose the entire wastegate system may result in repeated wastegate solenoid failure.
- A proper diagnosis of this code should begin with a basic overview of the turbocharger system
- Turbocharging is a form of forced air induction
- Forced air induction is a means of introducing excessive amounts of air into an engine in order to promote gains in horsepower
- Where a naturally aspirated engine utilizes vacuum created by downward piston movement to draw a controlled fuel/air mixture into the engine’s combustion chambers, the forced air induction engine has air and fuel forced into the combustion chambers using an alternately driven device
- Turbochargers are simply engine driven air compressors, designed to accomplish this task
- Turbochargers use the pressure from engine exhaust to propel impellers in a two chambered housing
- The two chambers are totally separate one from another
- Engine exhaust pressure turns the impeller in chamber “A”, which in turn spins turbine in chamber “B”
- The impeller in chamber “B” gathers fresh air through the turbocharger intake system (and intercoolers) and forces the cooler, denser air into the engine
- The cooler that the air temperature can become prior to entering the forced air induction device, the denser it will be when it reaches the combustion chamber
- Denser air allows fuel to atomize more efficiently and promotes increased horsepower.
To prevent overboost, most modern forced air induction engines use some form of a wastegate valve, or boost pressure release valve, to relieve boost pressure at high RPMs
- The wastegate is typically held in the closed position by a spring-loaded rod attached to the outside of the wastegate door
- As boost pressure increases at the wastegate door, it pushes against the spring-loaded rod until the door is opened and pressure is routed away from the compression device preventing further boost
- BMP sensors, MAP sensors, engine and transmission temperature sensors, and knock sensors are used by the PCM to calculate a safe level of boost that also yields optimum engine performance results
- Solenoids, stepper motors, and pulse modulators are used to effectively open and close the wastegate valve in order to provide the maximum safe level of boost pressure at different RPMs.
A scanner or code reader, a digital volt ohmmeter, and access to a manufacturer’s wiring schematic will be necessary to successfully diagnose this code
Begin your diagnosis with a visual inspection of all wiring and connectors
- Repair or replace damaged, disconnected, shorted, or corroded wiring, connectors, and components as necessary
- Always retest the system after repairs are completed to ensure success.
If all system wiring, connectors, and components (Including fuses) appear to be in normal working order, connect the scanner (or code reader) to the diagnostic connector and record all stored codes and freeze frame data
- This information can be extremely helpful in diagnosing intermittent conditions that may have contributed to this code being stored
- After the codes are cleared, operate the vehicle to see if the code returns
- If the code fails to immediately return, you may have an intermittent condition
- Intermittent conditions can prove to be quite a challenge to diagnose and in extreme cases may have to be allowed to worsen before a correct diagnosis can be made.
Most overboost malfunctions will be related to the wastegate actuator (rod)
- Always check for proper wastegate door operation first (assuming that no other codes are present)
- By connecting a hand-held vacuum pump to the wastegate controller, you can test for proper operation of the wastegate door
- Pump the vacuum pump while carefully observing the wastegate door and actuator rod
- Compare the inches of vacuum required to activate the wastegate door (if it opens at all) to the manufacturer’s specifications and repair as necessary.
If you still haven’t found an obvious problem, test the electrical circuitry and connectors of the turbocharger boost sensor
- Confirm voltage and resistance values using manufacturer’s specifications and repair faults as necessary.