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P0029 – What Does It Mean & How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.

Definition

OBD-II Code P0029 - Engine Exhaust Valve Control Solenoid Circuit Range/Performance (Bank 2). This Diagnostic Trouble Code (DTC) is set when the PCM detects an Exhaust Valve Control Solenoid Circuit voltage that falls outside of the specified range.

Meaning

The Exhaust Solenoid controls the opening of the exhaust valves to allow for exhaust gases to flow out of the engine. The Solenoid is controlled by applying a ground signal that moves a plunger into contact with spring-loaded metal contacts, closing them together. 

When closed, current can then pass between the Solenoid Control circuit and Ground through these contacts, allowing voltage to be applied across the Exhaust Valve Control Solenoid coil windings. This message appears when the engine control module (ECM) observes that the variable valve lift solenoid for bank 2's exhaust valves takes too long to engage or does not engage.

Causes

The following are common causes of this issue:

  • The bank 2 exhaust valve solenoid is faulty, causing the valve lift to stay in place.
  • Faulty PCM
  • Open circuit in the Exhaust Solenoid Control Circuit between the solenoid and ECM (B2S1)
  • Short to ground on the Exhaust Solenoid Coil (B2S1) at the PCM. This provides voltage to power the coil but does not send it through the control circuit.

Symptoms

Symptoms of a P0029 trouble code may include:

  • Worn Out Exhaust Solenoid
  • Engine long crank time before starting
  • The engine does not start or starts and then stalls out after a few seconds
  • The service engine lights on
  • The engine will run erratically during idle and when accelerated

Diagnosis

  1. Visually verify the electrical connections and wiring harness to the bank 2 exhaust valve solenoid.
  2. Check the validity of the codes, clear and see whether they return.
  3. The variable valve lift may be activated by the test solenoid, by checking to see if functioning properly.
  4. Check for an internal short or open circuit to the solenoid specifications.
  5. Follow the manufacturer's precise tests for further evaluation.

Common mistakes

The following are common mistakes when diagnosing the trouble code P0029:

Not verifying all potential causes of the failure before replacing parts. Some technicians make assumptions about which component is faulty, only to replace it without checking for other issues, especially without the use of sophisticated tools like a test solenoid to diagnose the problem.

How serious is this?

The P0029 trouble code is serious, as the vehicle will not properly run. This may lead to other more serious problems with the engine. If left unattended, these problems can lead to detrimental overheating of the engine. May even leave you stalled out after starting, long crank times before starting, or random engine surges when idle.

What repairs can fix the code?

The following are solutions that may fix this problem:

  • Check the Bank 2 Exhaust Valve Solenoid for a fault. It can be checked by measuring the resistance of the valve lift solenoid. 
  • Check for an open or short circuit in the control circuit between the PCM and valve lift solenoid.
  • If there is no evidence of a failed exhaust valve lift solenoid, check for an intermittent fault in the PCM signal circuit between it and its B2S1 input from the intake valve lift timing solenoid.
  • Inspect for a faulty crank angle sensor, cam angle sensor, or camshaft position sensor. With these sensors in place, they may be failing intermittently and causing it to set the DTC.
  • Repair any wiring or connections in the control circuit between PCM and solenoid.

Related codes

Code P0732: This trouble code refers to the engine exhaust camshaft or crankshaft position sensor.

Code P000A: This trouble code refers to a system malfunction of the variable valve lift and timing control solenoid bank 1.

Code P0030: This trouble code refers to a fault in the Evaporative Emission (EVAP) control system.

Code P0031: This trouble code refers to a fault in the EVAP Vapor Pressure Sensor circuit.

Code P0037: This trouble code refers to a fault in the engine cooling fan relay control circuit.

Code P0039: This trouble code refers to a fault in the Secondary Air Injection System (AIR) monitor solenoid 1 circuit.

How much does it cost to fix the P0029 code?

Replacing a failed exhaust valve lift solenoid, and its wiring circuit may be as low as $300 to $400.

Chips and pigtails for the PCM start at $200. 

Any wiring or connector repairs on the control circuit will cost more depending on what is damaged.

The test solenoid can run as low as $100, but those with more sophisticated diagnostic equipment will cost more. 

Conclusion

The P0029 trouble code is serious, as the vehicle will not properly run. This may lead to other more serious problems with the engine. If left unattended, these problems can lead to detrimental overheating of the engine. May even leave you stalled out after starting, long crank times before starting, or random engine surges when idle.

While there are several causes for this type of check engine light to turn on, an inspection of all potential faults should be done prior to replacing parts in order to save yourself time and money down the road.

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