P0028

What Does Code P0028 Mean?

DTC P0028 signifies an detected “Intake Valve Control Solenoid Circuit Range/Performance” issue on Bank 2. This code specifically points to a malfunction within the Variable Valve Timing (VVT) or Variable Valve Lift (VVL) system’s intake camshaft oil control valve (OCV), also commonly referred to as the VVT solenoid, for the cylinder bank that does not contain cylinder #1 (Bank 2). The Engine Control Module (ECM) or Powertrain Control Module (PCM) monitors the electrical circuit and hydraulic response of this solenoid. When the ECM commands the intake VVT solenoid on Bank 2 to adjust camshaft timing or valve lift, it expects a corresponding change in electrical parameters (e.g., current draw, resistance) and, subsequently, a feedback signal from the Camshaft Position (CMP) sensor indicating the desired cam angle or lift has been achieved or is within a specified range. If the ECM detects that the electrical circuit for the solenoid is outside its predefined operational voltage or current range, or if the expected camshaft position adjustment does not occur within a specified time frame or magnitude after the solenoid is commanded, it registers a “Range/Performance” fault and stores P0028.

Common Symptoms

• Illuminated Malfunction Indicator Lamp (MIL)
• Reduced engine power or sluggish acceleration
• Rough idling or stalling
• Increased fuel consumption
• Engine hesitation or misfires under specific load conditions
• Difficulty starting the engine (less common, but possible if timing is severely off)
• Audible ticking or rattling noises from the engine (due to lack of oil pressure to VVT components)

What Causes the Code P0028?

• Faulty Intake VVT/OCV Solenoid (Bank 2) itself, exhibiting an internal electrical short, open circuit, or mechanical sticking due to sludge or debris.
• Electrical wiring harness issues, including open circuits, short circuits to ground or voltage, or high resistance within the solenoid’s power or control circuit on Bank 2.
• Corroded or damaged electrical connector for the Intake VVT/OCV Solenoid (Bank 2), leading to intermittent or poor electrical contact.
• Insufficient or incorrect engine oil level and/or contaminated engine oil, hindering the hydraulic operation of the VVT system.
• Clogged oil passages supplying oil pressure to the Intake VVT/OCV Solenoid or the VVT phaser on Bank 2.
• A physically stuck or damaged VVT cam phaser (actuator) on Bank 2, preventing the camshaft from adjusting even with a functioning solenoid.
• Rarely, an internal ECM/PCM fault affecting the driver circuit for the Bank 2 Intake VVT solenoid.

How to Diagnose and Troubleshoot

A systematic diagnostic approach is crucial for P0028. Begin by utilizing an OBD-II scan tool to confirm the DTC and review freeze frame data, which can provide valuable insight into engine conditions at the time the fault was set. Clear the DTCs and attempt to replicate the conditions if possible.

1. Visual Inspection: Begin by visually inspecting the wiring harness and electrical connector for the Bank 2 intake VVT solenoid. Look for any signs of damage, chafing, corrosion, or loose connections. Ensure the solenoid is properly seated. Check the engine oil level and condition; low or dirty oil can severely impact VVT system performance.
2. Electrical Testing of Solenoid (Unplugged):
   • Resistance Check: With the engine off and the solenoid connector disconnected, use a Digital Multimeter (DMM) to measure the resistance across the two terminals of the VVT solenoid itself. Compare this reading to the manufacturer’s specifications (typically 6-12 ohms). An open circuit (infinite resistance) or a short circuit (near zero ohms) indicates an internal solenoid fault.
   • Solenoid Actuation Test: Apply 12V and ground directly to the solenoid terminals from a fused power source (e.g., battery). A functional solenoid should produce an audible click as it actuates. Visually inspect the plunger movement if possible. Be brief to avoid overheating.
3. Electrical Testing of Wiring Harness (Connector Side):
   • Power Supply Check: With the ignition ON (engine OFF), backprobe the power supply wire at the VVT solenoid connector (harness side). Expect to see battery voltage (approx. 12V). If no voltage, trace the circuit back to the fuse box and relevant relays.
   • Ground/Control Circuit Check: Identify the ground or control wire from the ECM. With the solenoid disconnected and ignition ON, check for continuity to chassis ground (though the ECM typically provides a switched ground for PWM control). For the control circuit, a DMM may show a fluctuating voltage or an average voltage as the ECM attempts to control it (an oscilloscope provides much more detailed insight into the PWM signal).
   • Continuity/Short to Ground/Voltage: With the battery disconnected and the ECM connector also disconnected, check for continuity between the solenoid’s control wire and chassis ground (short to ground) or battery positive (short to voltage). Also, check for open circuits within the wire itself.
4. Functional Test with Scan Tool: Using an advanced diagnostic scan tool with bidirectional control, command the Bank 2 intake VVT solenoid ON and OFF. While commanding, monitor live data for the Bank 2 intake camshaft position sensor. An audible click from the solenoid should be heard, and a noticeable change in the CMP angle should be observed. Lack of response from the CMP sensor, even with an audible click, could indicate a stuck cam phaser or clogged oil passages.
5. Oil Pressure Verification: While not directly a circuit test, inadequate oil pressure or sludge within the VVT system can mimic a solenoid performance issue. If possible, verify engine oil pressure at idle and higher RPMs against specifications.

Recommended Repairs and Solutions

Based on the diagnostic findings, the following repairs are typically recommended:

• Replace the Intake VVT/OCV Solenoid (Bank 2): This is the most common resolution for P0028, especially if electrical testing confirms an internal fault with the solenoid or if it fails the actuation test. Always use OEM or high-quality aftermarket solenoids to ensure proper function and longevity.
• Repair or Replace Wiring Harness/Connector: If the diagnostic steps identify an open circuit, short, or high resistance in the wiring or a damaged connector, repair or replace the affected section of the wiring harness. Ensure all connections are secure and corrosion-free.
• Perform Engine Oil Change and Filter Replacement: If the engine oil is low, dirty, or incorrect viscosity, perform an oil and filter change using the manufacturer-specified oil type and viscosity. This can often resolve performance-related VVT issues by restoring proper hydraulic pressure and preventing sludge accumulation.
• Clean VVT Oil Passages: In some cases, sludge or debris can block the oil passages leading to the VVT solenoid or phaser. While difficult to access without significant disassembly, some systems allow for targeted flushing or cleaning. If a severe blockage is suspected, further engine tear-down may be necessary.
• Replace VVT Cam Phaser (Actuator): If the solenoid tests good electrically and hydraulically, but the camshaft position still does not respond to commands, the VVT cam phaser itself on Bank 2 may be stuck or damaged. This is a more involved repair requiring timing component removal.
• ECM/PCM Replacement: As a last resort, if all other components and wiring test perfectly, an ECM/PCM fault affecting the solenoid driver circuit might be present. This is rare and should only be considered after exhaustive testing of all other possibilities.

Mechanics’ Tips: Always cross-reference the specific VVT system design for the vehicle make and model, as configurations vary. When replacing VVT solenoids, ensure the new part includes any necessary O-rings or seals to prevent oil leaks. After any VVT system repair, clear the DTCs and perform an extended test drive to confirm the repair and ensure the code does not return. Pay close attention to engine performance during the drive, particularly during conditions that might trigger the VVT system (e.g., cruising, light acceleration).