P0029

What Does Code P0029 Mean?

The diagnostic trouble code P0029 indicates an issue with the Exhaust Valve Control Solenoid Circuit on Bank 2 operating outside its specified Range/Performance parameters. Bank 2 refers to the cylinder bank that does not contain cylinder #1. This code specifically targets the electrical circuit and/or the functional performance of the solenoid responsible for controlling the exhaust camshaft phaser (also known as a VVT/VCT actuator) on the exhaust side of the engine. The Engine Control Module (ECM), often referred to as the Powertrain Control Module (PCM), continuously monitors the electrical characteristics (voltage, current, resistance) of the solenoid circuit, as well as the actual camshaft position relative to the commanded position. When the ECM detects that the solenoid’s circuit is drawing current or exhibiting voltage outside of the expected operational range, or if the feedback from the camshaft position sensor indicates that the exhaust camshaft on Bank 2 is not achieving or maintaining its target position despite the solenoid being commanded, P0029 is set. This differentiates it from a simple open or short circuit code, suggesting the circuit may be complete but malfunctioning in a way that impairs the solenoid’s ability to precisely modulate oil flow to the camshaft phaser, thereby affecting valve timing.

Common Symptoms

• Illumination of the Check Engine Light (CEL) or Malfunction Indicator Lamp (MIL).
• Noticeable reduction in engine power and overall performance, particularly during acceleration.
• Rough or erratic idling, sometimes leading to engine stalling, especially when cold or at low RPMs.
• Increased fuel consumption due to inefficient valve timing.
• Audible engine noises such as ticking, rattling, or knocking, which may originate from the VVT system components or result from incorrect valve timing.
• Potential difficulty starting the engine.
• Failure of emission tests due to improper combustion and increased emissions.

What Causes the Code P0029?

• Faulty Exhaust VVT/VCT Solenoid (Bank 2): The solenoid itself can fail electrically (internal open, short, or resistance out of spec) or mechanically (plunger sticking, clogged internal screens).
• Wiring Harness Issues: Damaged, corroded, frayed, or shorted wiring within the solenoid’s electrical circuit, including poor connections at the solenoid connector or the ECM/PCM connector.
• Contaminated or Low Engine Oil: VVT systems rely heavily on clean engine oil at the correct viscosity and adequate pressure to operate the camshaft phasers. Sludge buildup, incorrect oil type, or insufficient oil level can impede solenoid and phaser function.
• Clogged Oil Passages: Restricted oil passages leading to the VVT solenoid or the camshaft phaser can prevent proper oil flow, impacting solenoid effectiveness and phaser actuation.
• Faulty Exhaust Camshaft Phaser/Actuator (Bank 2): While P0029 often points to the solenoid or its circuit, a mechanically stuck or damaged phaser can cause the ECM to detect a “performance” issue if the cam cannot reach its commanded position.
• ECM/PCM Malfunction: Although rare, an internal fault within the ECM/PCM affecting the VVT solenoid driver circuit can trigger this code.

How to Diagnose and Troubleshoot

A systematic diagnostic approach is crucial for P0029. Begin with the simplest checks and progress to more complex electrical and mechanical tests:

1. Visual Inspection: Start by visually inspecting the exhaust VVT solenoid on Bank 2. Check its electrical connector for corrosion, damage, or loose pins. Trace the wiring harness for any signs of fraying, cuts, or heat damage. Verify the engine oil level and condition. Contaminated, dirty, or low oil can severely impact VVT operation.
2. OBD-II Scanner Data Analysis:
   • Connect an advanced OBD-II scanner and confirm P0029 is present. Check for any related VVT codes (e.g., P0027, P0028, or camshaft position sensor codes) that might provide additional context.
   • Review freeze frame data associated with P0029 to understand engine conditions (RPM, load, temperature) when the fault occurred.
   • Monitor live data parameters: specifically, Bank 2 Exhaust Camshaft Position (Desired vs. Actual) and VVT Solenoid Command Percentage/Duty Cycle. Observe if the actual cam position deviates significantly from the desired position.
   • If available, perform a bidirectional control test (actuator test) on the Bank 2 Exhaust VVT Solenoid. Listen for a distinct click from the solenoid and observe if the actual camshaft position changes in response to the command.
3. Electrical Circuit Testing (Using a Digital Multimeter – DMM):
   • Solenoid Resistance: Disconnect the electrical connector from the exhaust VVT solenoid (Bank 2). Using a DMM set to ohms, measure the resistance across the two terminals of the solenoid itself. Compare this reading to manufacturer specifications (typically 6-15 ohms). An out-of-spec reading (too high, too low, or an open circuit/infinite resistance) indicates a faulty solenoid.
   • Power and Ground Supply to Solenoid: With the key in the “ON” position (or engine running, depending on circuit design), check for battery voltage at the solenoid harness connector. One terminal typically provides constant or switched battery voltage, and the other is a pulsed ground signal from the ECM. If no power, trace the circuit back to the fuse box. If no ground signal, proceed to ECM circuit testing.
   • Circuit Continuity: Disconnect the ECM/PCM connector and the solenoid connector. Using the DMM, check for continuity (low resistance) between the corresponding pins of the harness at both ends. Also, check for shorts to ground and shorts to voltage within the wiring harness.
4. Engine Oil Pressure Check: If electrical tests pass, and oil contamination/level has been ruled out, use a mechanical oil pressure gauge to verify actual engine oil pressure at various RPMs against manufacturer specifications. Low oil pressure directly impacts VVT system functionality.
5. Solenoid Inspection (If Accessible): If all electrical tests pass and the solenoid is still suspected, remove the solenoid and visually inspect its screens for debris or sludge. While cleaning might offer a temporary fix, replacement is often more reliable.

Recommended Repairs and Solutions

Once the root cause is identified through meticulous diagnosis, the following repairs are commonly performed to resolve P0029:

• Replace the Exhaust VVT/VCT Solenoid (Bank 2): This is the most common repair for P0029, especially if electrical tests reveal the solenoid itself is faulty or if the actuator test shows no response. Always use an OEM or high-quality aftermarket replacement part to ensure proper operation and longevity.
• Repair or Replace Damaged Wiring/Connectors: If the diagnostic process identified an issue with the wiring harness or electrical connectors, perform precise repairs (soldering, heat-shrinking) or replace the affected section of the harness or connector.
• Perform an Engine Oil Change: If the engine oil was found to be low, dirty, or incorrect, drain and refill with the manufacturer-specified oil type and viscosity. Replace the oil filter simultaneously. This is a critical first step if oil-related issues are suspected, as clean oil is paramount for VVT system health.
• Address Low Engine Oil Pressure: If an actual low oil pressure condition is confirmed, diagnose and repair the underlying cause, which could include a faulty oil pump, a clogged oil pickup tube, worn engine bearings, or a faulty oil pressure relief valve.
• Flush Oil Passages: In cases of severe sludge buildup, a specialized engine flush might be necessary to clear restricted oil passages leading to the VVT system. However, this should be done cautiously and preferably by a professional.
• Replace the Exhaust Camshaft Phaser/Actuator (Bank 2): If the solenoid and its circuit test perfectly, and oil pressure is adequate, the camshaft phaser itself might be mechanically sticking or damaged internally. This is a more involved repair and typically requires specialized tools and expertise.

Mechanic’s Tips: After any repair, clear the diagnostic trouble codes using an OBD-II scanner. Perform a thorough test drive under various engine loads and RPMs to confirm that the repair has resolved the issue and the code does not return. Pay close attention to any changes in engine performance or new noises. Consistent engine oil maintenance with the correct oil type is critical for preventing future VVT-related issues.