Air Assisted Injector Control Circuit or Circuit Low
The PCM has detected a malfunction in the control circuit for the air assisted injector. The air assisted injector solenoid is part of this circuit.
Code Set Parameters
When the PCM detects a voltage or resistance reading that is not within a predetermined limit, a code will be stored and a malfunction indicator may be illuminated. Some models may require multiple failure cycles in order for the malfunction indicator lamp to be illuminated, others activate the lamp on the initial failure.
The two most common causes of this code being stored are a defective air assisted injector control solenoid or a lethargic heated upstream oxygen sensor in the affected engine bank. Other causes may include shorted, open, damaged, or corroded circuits or electrical connectors, or a faulty PCM. Techs report that this code is also exhibited in error at times and requires reprogramming of the PCM in order to correct the condition.
Components are sometimes replaced in error when reprogramming is required (and vice-versa). Air assisted injector control solenoids are often replaced when a faulty oxygen sensor is the culprit.
- The air assisted injection system uses air gathered from either the throttle body opening or an alternate opening in the intake
- A solenoid, commanded by the PCM, is used to administer the air to an area in which each individual fuel injector sprays
- The air is used to promote more efficient fuel atomization
- Air assisted injection techniques are used in some naturally aspirated gasoline engines as well as diesel engines
- It is most common in direct fuel injection systems.
Most air assisted injection systems use a solenoid to allow (or disallow) clean air from outside the engine to enter the fuel injector spray area often using a “swirl” effect
- Some control solenoids are mounted directly to the intake and have integrated openings that air passes through
- Other systems utilize vacuum hoses connected to a remotely mounted solenoid to introduce cooler, denser air into the fuel injector spray area
- Regardless of which system is used, the PCM regulates air flow and monitors voltage, resistance, and drivability data to make sure that the system is operating properly.
A scanner or code reader and a digital volt/ohmmeter will be very helpful in diagnosing this code successfully.
Begin your diagnosis by visually inspecting all wiring and connectors
- Look for shorted or burned wiring and replace circuitry and connectors as required
If the system wiring, connectors, and components appear to be in normal working order, connect the scanner to the diagnostic connector and record all stored trouble codes and freeze frame data
- This information can be extremely helpful in diagnosing intermittent conditions that may have contributed to this code being stored
- After the codes are cleared, operate the vehicle to see if the code returns
- If the code fails to immediately return, you may have an intermittent condition
- Intermittent conditions can prove to be quite a challenge to diagnose and in extreme cases may have to be allowed to worsen before a correct diagnosis can be made.
Don’t forget to inspect vacuum hoses and mounting gaskets for discrepancies
- Repair or replace damaged, disconnected, or corroded components and/or wiring/connectors as required
- Retest the system to ensure that repairs were successful.
If the code returns immediately, obtain a wiring schematic and/or a connector view for the air assisted injection system of your vehicle
- Check for voltage and ground signals at the air injection solenoid and compare your findings with manufacturer’s specifications
- Repair open, shorted, or disconnected circuits as necessary
- If there is no voltage present, check system fuses and relays
- If the ground is not present, look for loose or corroded ground straps and wires near the battery and engine block
Most systems use a constant battery voltage supply to the solenoid with the PCM providing a ground pulse that activates the solenoid and allows air to pass into the combustion chamber
- With the scanner connected you may be able to command the solenoid off and on, manually
- Check solenoid operation as the solenoid is commanded with the scanner
- If the solenoid electrical connector voltage is in line with manufacturer’s specifications, use the digital volt ohmmeter to test solenoid resistance and compare your findings with manufacturer’s specs
- Replace the solenoid if resistance levels do not coincide with manufacturer’s specifications.
If the solenoid, wiring, and connectors check out, perform a circuit resistance and continuity test
- Always disconnect any related computerized controllers from the circuit prior to testing resistance
- Repair or replace any shorted or open circuits and retest the system to make sure that it is repaired correctly.
If the system circuitry appears to be normal, suspect a defective PCM
- Remember that PCM failure is rare.