OBD-II trouble code
P0067: Air Assisted Injector Control Circuit High
The air-assist injector control circuit is reading high. On a solenoid circuit that usually means the module never managed to pull the line down — and a two-minute resistance check across the coil settles most of it.
Quick facts
- System
- Powertrain
- Category
- Fuel Injectors
- Severity
- Low severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $70 – $520
- DIY difficulty
- Intermediate DIY
What does P0067 mean?
P0067 sets when the module tries to operate the air-assist valve and the control line stays at a higher voltage than it should.
On a solenoid circuit this has a short list of explanations, which is the good news about this particular code. The module typically feeds the solenoid from a supply and switches the other side to ground to make it operate. While it is switching, it watches the line. If the line will not come down, one of three things is true: the coil is open, so no current can flow no matter what the module does; the wiring between them is broken, with the same effect; or the line is being held up by contact with a power source the module cannot overcome. Everything else is a variation on those.
That makes the resistance measurement across the solenoid's two terminals the highest-value test on this code, and it takes about two minutes. A solenoid winding is a coil of fine wire, and coils fail open far more often than they fail any other way — vibration and heat cycling eventually break a conductor, or the joint where the winding meets the terminal fatigues. An infinite reading condemns the valve on the spot. A sensible reading, matching the manufacturer's figure, clears it just as decisively and sends you into the harness with a much narrower search.
The second characteristic worth understanding is that this fault is silent. An air-assist valve that never opens produces no noise, no warning behaviour and nothing a driver would think to mention. The system is a cold-start refinement, so what is actually lost is atomisation quality during the first minute or so from a cold start — a period in which a disproportionate share of a vehicle's total hydrocarbon emissions is produced, before the catalyst is hot enough to help. This is why P0067 is very often discovered at an inspection or during unrelated work rather than reported as a complaint, and it is why owners frequently push back on repairing it. The honest answer is that the car will not drive any worse, and that the fault still costs something real every time the engine is started cold.
The third point is environmental. The air-assist valve lives in the engine bay, usually with air or vacuum hoses attached, in a position chosen for hose routing rather than for durability. Heat cycling hardens the connector, embrittles the pigtail insulation and eventually cracks the hoses. Because a hose problem cannot cause a high circuit but often accompanies one on a component of this age, it is worth inspecting the hoses in the same visit rather than closing the job on the electrical repair alone.
The engine is fully driveable throughout and there is no mechanical risk in continuing to use the vehicle while the repair is arranged.
Common causes
- Open winding inside the air-assist solenoid, the most common single cause of a high reading
- Broken control wire between the module and the valve
- Connector not fully seated, or a terminal backed out of the housing so the circuit is open
- Control wire shorted to a power feed, holding the line up against the module's driver
- Heat-embrittled pigtail insulation cracking and breaking the conductor at the valve
- Corroded terminals at the valve connector after years of engine-bay heat cycling
- Incorrect replacement solenoid with a winding resistance outside the expected range
- Failed low-side driver in the engine control module, which is uncommon and confirmed only after the wiring is cleared
Symptoms
- Check engine light on with P0067 stored and no driver complaint at all
- Fault found during an inspection or unrelated service rather than noticed while driving
- Slightly unsettled idle in the first minute after a cold start on some engines
- Elevated hydrocarbon reading on a tailpipe emissions test
- Air-assist valve silent when commanded on engines where it is normally audible
- Companion code P0065 where the module also judged the system's effect as absent
- Blown fuse on the shared circuit where the control wire is contacting power
- Completely normal driving once the engine is warm
Diagnostic steps
- 1.Measure resistance across the two solenoid terminals at the valve and compare with the manufacturer's figure. An open reading condemns the valve immediately and a normal reading clears it just as firmly.
- 2.Check that the connector is fully seated and that no terminal has backed out, since an unseated plug produces exactly the same reading as an open coil.
- 3.Inspect the pigtail insulation for heat embrittlement and cracking close to the valve, where the conductor most often breaks.
- 4.Test continuity of the control wire from the module connector to the valve connector to locate a break in the harness.
- 5.With the control wire disconnected at both ends, check for voltage present on it. Voltage on a disconnected wire proves a short to power.
- 6.Confirm the valve's supply side is present and correct before assuming the fault is on the control side.
- 7.Command the valve on with a scan tool while watching the circuit with a meter or scope, and see whether the module attempts to switch it at all.
- 8.Inspect the air and vacuum hoses at the valve while it is accessible, since components of this age frequently have cracked hoses alongside an electrical fault.
- 9.If everything external tests correct, back-probe the module connector while commanding the valve to confirm or exclude a failed driver.
- 10.After repair, complete a cold-start cycle from a genuine cold soak and confirm the code does not return, because the function only runs when the engine is cold.
Repair cost
$70 – $520
An unseated connector or a re-terminated pigtail is the cheapest outcome at $70 to $200. The air-assist solenoid itself is $60 to $260 in parts with 0.5 to 2 hours of labour, giving a fitted total of roughly $170 to $480 depending on how buried it is. Repairing a broken or shorted control wire runs $120 to $300, most of it in locating the break. Diagnosis is $80 to $160, and on this code it is unusually good value because the resistance check across the coil resolves the majority of cases before any part is ordered. Replacing perished air hoses at the same time adds $20 to $80.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with air-assisted injection system service preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
This is an intermediate DIY job. It usually involves diagnostic steps, specialty parts, and some careful work in tight spaces. If you have the tools and a service manual or trustworthy video for your specific vehicle, it is achievable in a weekend. Otherwise, a competent independent shop will be faster.