DTC P0067 – “Air-Assisted Injector Control Circuit High.”

✅ What P0067 Means

The ECM detects voltage too high in the air-assisted injector control circuit.

This system uses an air control solenoid/valve to deliver air to the injector at cold start to improve atomization.
A high signal usually means:

Open circuit in control wire

Poor ground

Faulty air-assist solenoid

Stuck solenoid

Corrosion at connector

ECU driver issue (rare)

✅ Common Causes

Electrical

Open in control wire (ECM → Air Assist Solenoid)

Short to voltage in harness

Poor connector contact

Corroded or damaged pins

Bad ground for solenoid

Faulty air-assist solenoid (internal open)

Mechanical / System

Solenoid stuck closed (rare for high signal)

Vacuum lines disconnected or blocked

ECM

Faulty ECM driver (last possibility)

✅ Symptoms

Hard cold start

Rough idle on cold engine

High fuel consumption

Misfire at start-up

MIL (Check Engine ON)

🔧 Step-by-Step Diagnostic Procedure

1. Visual Inspection

🌟 Check the air-assist injector solenoid
🌟 Inspect harness for cuts, rubbing, oil soak
🌟 Check for corrosion in the connector
🌟 Verify vacuum hose routing to solenoid
🌟 Confirm connectors are fully seated

2. Check Power Supply

Most systems supply battery voltage (12V) to the solenoid, and the ECM controls the ground side.

Use a multimeter:

1. Turn ignition ON.

2. Check the power wire to the solenoid.

Should be 10–14V.

If voltage is too high (above 14V) → alternator overvoltage (rare).

3. Check the Control Wire (ECM → Solenoid)

Set multimeter to DC voltage.

Backprobe the control wire

Start engine or command solenoid using a scan tool

If voltage stays HIGH all the time (battery level):
🎀 Open circuit in solenoid
🎀 Broken wire from solenoid to ECM
🎀 Faulty solenoid coil

4. Measure Solenoid Resistance

Disconnect solenoid and measure.

Typical coil value: 20–40 ohms (varies by model; even 15–50Ω is normal range).

📌 If the solenoid has infinite resistance (open) → Replace the solenoid.
📌 If resistance is extremely high (>100Ω) → Replace solenoid.

5. Check Ground

Using multimeter continuity check:

Solenoid ground → chassis
If loose or corroded → repair.

6. Check Wiring to ECM

If solenoid is good:

🌟 Check for open circuit
🌟 Check for short to battery
🌟 Perform wiggle test for intermittent breaks

7. ECM Driver Test (Last Step)

If:

Power is OK

Ground is OK

Solenoid coil is OK

Wiring is OK

🎀 ECM may not be pulling the voltage low
🎀 Replace or repair ECM

🛠 Most Common Fixes

Cause Fix

Open circuit in solenoid coil Replace air-assist injector solenoid
Broken wire (ECM → solenoid) Repair/replace harness
Bad connector Clean pins / replace connector
Short to voltage Trace and repair wiring
Poor ground Clean/repair ground
Faulty ECM (rare) Reflash or replace ECM

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