What Does P004D Mean?
The PCM has detected that the turbocharger/supercharger boost control 'B' circuit voltage or signal is higher than expected. This indicates a short to battery voltage or an excessively high signal in the secondary boost control solenoid circuit. The driver may experience overboosting from the secondary turbo system or the vehicle may enter limp mode for engine protection.
Common Causes
35%
Short to battery voltage in the boost solenoid 'B' control wiring
25%
Internally shorted boost control solenoid 'B' (coil shorted to supply)
20%
Corroded connector with cross-pin contact at the solenoid or PCM
20%
PCM boost control 'B' driver failure (output stuck high)
Diagnostic Steps
1
Disconnect the boost solenoid 'B' and with KOEO, check for voltage on the PCM control wire — it should be near 0V when not commanded. Voltage present indicates a short to power.
2
Measure the solenoid coil resistance and check for shorts between the control terminal and the power supply terminal.
3
With both the solenoid and PCM disconnected, check the control wire for voltage — any voltage confirms a harness-level short to a power source.
4
Inspect the wiring harness for areas where the control wire runs alongside or crosses power-carrying wires, looking for chafing or insulation breakdown.
5
If all wiring tests clean, reconnect and command the solenoid with a bi-directional scan tool while monitoring current draw to verify proper PCM driver operation.
Estimated Repair Cost
$100 - $550
Parts + labor, varies by vehicle and location
The PCM has detected that the turbocharger/supercharger boost control 'B' circuit voltage or signal is higher than expected. This indicates a short to battery voltage or an excessively high signal in the secondary boost control solenoid circuit. The driver may experience overboosting from the second...
The most common cause of P004D (Turbocharger/Supercharger Boost Control "B" Circuit High) is: Short to battery voltage in the boost solenoid 'B' control wiring
Typical repair costs for P004D range from $100 to $550, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Use caution. A shorted-high condition may cause the secondary boost solenoid to remain energized, potentially leading to overboosting. If you notice excessive power, unusual turbo noises, or detonation (pinging/knocking), stop driving immediately to prevent engine damage.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P004D to identify the root cause.
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Quick Info
Category
Powertrain
System
Forced Induction / Turbocharger
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
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