|Code||Fault Location||Probable Cause|
|P0034|| Turbocharger (TC) wastegate regulating valve -circuit low |
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|Wiring short to earth, TC wastegate regulating valve, ECM|
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What Does Code P0034 Mean?
Code P0034 is a generic powertrain code that is used in both turbocharger and supercharger applications. When exhaust pressure builds up at the turbocharger/supercharger inlet, a pressure outlet hose on the turbocharger or supercharger directs excess pressure to the wastegate for release. On some boost solenoids, there may also be a vent to atmosphere or a bypass directly into the intake. The bypass valve or boost solenoid actuates the wastegate at a certain pressure, allowing boost pressure to remain within the set allowances for the vehicle. It is controlled by the engine/powertrain control module (PCM).
The boost solenoid or bypass valve is normally in the closed position. When pressure builds to the vehicle’s boost parameters, the solenoid switches, and the wastegate can be actuated to release pressure. Should the solenoid fail to switch, excess pressure can cause turbocharger or engine damage from excess boost. However, if the solenoid remains in the open position, the turbocharger/supercharger’s inlet pressure will be insufficient to maintain proper boost for engine performance. DTC P0034 will be set in the PCM.
Note: Circuit Low Input codes are often the result of low battery voltages (that can have many possible causes), bad connections across electrical connectors or previously repaired wiring, as well as corrosion in electrical connectors. Other possible causes of low input voltages include poor installation of aftermarket components, poor quality aftermarket components like fuses, relays, and switches, and modification of the electrical system that could include the use of conductors that are not rated for use in a particular application. However, poor connections often result in high resistances in some parts of the circuit, which is why it is important to perform resistance and continuity checks during the diagnostic procedure.
What are the common causes of code P0034 ?
- Wiring chewed by a rodent
- Failed boost control solenoid
- Powertrain control module failure
- Poor connection at boost solenoid connector
- Moisture or corrosion in the boost solenoid connector
What are the symptoms of code P0034 ?
- When DTC P0034 is set, the engine light is illuminated.
- Should the boost solenoid be stuck in the open position, decreased engine performance is the most obvious result, along with decreased fuel efficiency.
- If the solenoid is stuck in the closed position, engine performance may be exaggerated with a possible overboost condition. This can cause internal engine damage, turbocharger or supercharger damage or failure, and oil leaks.
How do you troubleshoot code P0034 ?
DTC P0034 will set anytime the engine is running under normal operating conditions and the solenoid position and the commanded position do not match for a set period of time per the manufacturer.
Test the Boost Solenoid
Because of its simplistic design, the first step in diagnosing code P0034 is to check the boost valve itself. Disconnect the boost solenoid and remove it from the vehicle. On the intake end of the valve, blow air orally through the boost solenoid. At rest, the solenoid should allow air to pass through like a straw. If air does not pass through the boost solenoid may be blocked or stuck and should be replaced.
Test the solenoid actuation with a battery source. Attach a positive 12-volt source to the positive terminal of the solenoid, then attach a ground to the negative terminal on the solenoid. The solenoid will click audibly, indicating that the solenoid has switched. Disconnect and reattach the power source multiple times to ensure the solenoid switches consistently. While the wires are connected to the solenoid and it is in the switched position, blow through the solenoid again. Air should not be able to pass through. If air passes through, replace the boost solenoid.
Check the Boost Solenoid Wiring
Any issue with the wiring to the boost solenoid will cause code P0034 to set. Whether there is high resistance, a short to ground, short to voltage, or an open circuit, the same fault code will appear. Use a 12v probe with a test light to check the boost solenoid wiring.
As the complete boost solenoid circuit is under the hood of your car, check for moisture and corrosion at the connectors and along the wiring. Any moisture or corrosion in the connector can cause a poor connection that can set DTC P0034.
Short to Ground
Attach one lead of your probe to a bare ground. Disconnect the boost solenoid connector from the solenoid. With the ignition in the on position and the engine not running, probe the positive wire at the solenoid. There should be power at the positive wire, indicated by the test light on your probe illuminating. If the test light does not illuminate or is dim, trace the positive wire back to the PCM looking for a short to ground.
Short to Voltage
Attach one lead of your test probe to the positive battery terminal. With the ignition on and the engine not running, probe the negative or ground circuit at the boost solenoid connector. The test light should illuminate if ground is present. If ground is not present, trace the wire back to the PCM and repair any damaged, cracked, or broken sections of wire.
While checking for a short to ground or voltage, perform a wiggle test along each wire to help determine if there is a short. Keep close watch on the bulb, noting any changes when the wire is wiggled. Repair the wiring as necessary at any section that causes the bulb to go out.
Check the PCM
The control module supplies voltage and a ground to the boost solenoid. Test the PCM with the key on, engine off. With the test probe lead connected to a ground, probe the positive wire at the PCM connector. If the test light illuminates, the positive circuit is good. If it does not illuminate, the PCM is faulty. Test the ground circuit with the test probe lead connected to the positive battery terminal. If the test light illuminates, the ground circuit is good. If the test light does not light up, the PCM is faulty and needs to be replaced.
Codes Related to P0034
- P0033 – Turbocharger (TC) wastegate regulating valve -circuit malfunction
- P0034 – Turbocharger (TC) wastegate regulating valve -circuit low
- P0035 – Turbocharger (TC) wastegate regulating valve -circuit high
- P0234 – Turbocharger / Supercharger “A” Overboost Condition
- P0235 – Engine boost condition -limit not reached