P012D: Turbocharger/Supercharger Inlet Pressure Sensor A Circuit High (Downstream of Throttle Valve)

What it means

The module detects a high input from the turbocharger or supercharger inlet pressure sensor A circuit, downstream of the throttle valve.

At a glance

• Usually lights the check-engine light
• Affects emissions; the car can fail an emissions test

How it works

Sensor A reports pressure in the turbocharger or supercharger inlet passage downstream of the throttle valve. P012D sets when the control module sees the sensor A circuit input above its expected electrical range. An open signal circuit or a short to a supply voltage can make the input appear high even when actual pressure is ordinary.

Common causes

Most likely first.

1. Signal wire open
2. Connector pins corroded - high contact resistance
3. Supply wire pinched against B+ source

Symptoms

• Check engine light on

How to diagnose it

1. Save freeze-frame data and review live sensor A pressure to see whether the input is high or fixed under different engine conditions.
2. Inspect sensor A's connector and wiring for an unplugged connection, broken signal wire, corroded pins, or insulation damaged near a power source.
3. Check sensor A's reference supply and ground against the wiring diagram to rule out a supply or ground problem.
4. Test the signal wire for an open circuit and for a short to battery or another supply voltage.
5. If the circuit passes those checks, test sensor A's output against the manufacturer's specification.

Common fixes

• Reconnect and secure a loose sensor A connector.
• Repair an open or damaged sensor A signal wire.
• Repair a signal wire shorted to a supply source.
• Clean or replace corroded connector terminals.
• Replace sensor A if its output remains high with a verified circuit.

Can I keep driving?

If only the check-engine light is on, cautious driving may be possible, but avoid heavy acceleration or boost until the high input is diagnosed. The module may be using unreliable inlet pressure information.