P0067

Code

Generic P — Powertrain

Air Assisted Injector Control Circuit High

Brand: Generic

Type: P — Powertrain

Views: UK: 16 EN: 62 RU: 34

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Page language: EN

Causes

Short to battery/ignition-switched 12V on the injector control wiring
Open or corroded connector causing backfeed or false readings
Failed air-assisted injector solenoid (internal short or leakage)
Faulty PCM/ECU driver transistor producing a high output voltage
Blown or incorrect fuse/relay supplying the injector circuit
Aftermarket modifications or incorrect wiring

Symptoms

Illuminated MIL/Check Engine Light
Possible rough idle or misfire if the air-assist injector is disabled
Reduced engine performance or limp-home mode in some vehicles
No start or hard start in severe cases
Stored DTC P0067 (may be accompanied by related injector or ECU codes)

What to check

Read and record stored codes and freeze-frame data with a scan tool
Visual inspection of injector wiring harness, connectors, and terminals for damage or corrosion
Verify battery voltage and charging system are within spec
Check related fuses and relays for the injector/air-assist system
Backprobe the injector control connector and measure voltage with key ON and cranking
Measure DC resistance of the air-assisted injector solenoid (compare to spec)

Signal parameters

Key ON, engine OFF: expected control circuit voltage typically near 0 V (ground-referenced) or near battery voltage depending on driver topology — consult vehicle spec
When driver active: control signal often a low-side PWM pulsing to ground; voltage will switch between ~0 V (active) and battery voltage (~12 V) at PWM frequency
If circuit is high: idle/backprobe may show sustained near-battery voltage instead of pulsed switching
Injector solenoid DC resistance: typically 1–50 ohms depending on design (refer to vehicle spec)
No short to battery: between injector control pin and battery positive should be high resistance (open) except when driven

Diagnostic algorithm

Retrieve freeze-frame and relearn any related codes. Note conditions when code set (engine temp, RPM, load).
Visually inspect the air-assisted injector harness, connectors, and nearby wiring for damage, pinched areas, or corrosion. Repair obvious damage.
Verify fuse(s) and relay(s) for the injector/air-assist circuit are correct and functioning.
With the key ON (engine OFF), backprobe the injector control connector. Observe voltage. Normal behavior is driver-specific; consult service manual. A steady battery voltage suggests a short to power.
Measure injector solenoid DC resistance at the connector (unplugged) and compare to specification. Very low resistance suggests internal short; open/very high indicates open coil.
Crank engine (or command injector on with scan tool) and monitor the control signal with a DVOM and preferably an oscilloscope. Look for proper PWM switching or abnormal steady high voltage.
If wiring looks intact but voltage is high, disconnect the injector connector and measure voltage at the harness side. If high voltage persists with injector disconnected, suspect short to power in the harness or ECU driver fault.
Perform a continuity check between the control pin and the PCM connector to verify no unintended connections to battery or other circuits. Check for short to battery positive.
If harness and connector check OK, command the injector output OFF/ON from scan tool while monitoring the PCM terminal. If PCM cannot pull the line low or behaves abnormally, suspect ECU driver failure and confirm with manufacturer procedures.
If swap-testing is possible, swap the air-assisted injector with another known-good identical injector (if multiple exist) to see if the code follows the injector.
Repair damaged wiring, replace connector terminals, replace faulty injector if identified. If diagnostics point to PCM driver failure, follow OEM steps for ECU repair/replacement and programming.
After repairs, clear codes and perform road test or reproduction steps to confirm the fault is resolved.

Likely causes

Pinched or chafed harness contacting a constant 12V source
Injector connector pushed into contact with other power conductors
Injector solenoid internal short to battery return or internal resistance low
ECU output stage failed and clamped high
Corroded terminal creating intermittent high-voltage reading
Shorted splice or harness repair that tied the control circuit to battery voltage

Fault status

⚠️ Status

PCM detected HIGH voltage on air-assisted injector control circuit — circuit voltage exceeds expected threshold.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-2.5 hours

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