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What does code P2004 mean?

Code P2004 stands for Intake Manifold Runner Control Stuck Open Bank 1

The intake manifold directs air into the engine via a series of runners. To improve engine performance, many late-model vehicles use what’s referred to as an intake manifold runner control (IMRC) system. An IMRC system varies manifold runner length via electrically controlled butterfly valves. Typically, the valves are operated by a solenoid that receives commands from the powertrain control module (PCM). The PCM determines IMRC control based on inputs from the throttle position sensor (TP) and crankshaft position sensor (CKP).

Code P2004 indicates the PCM has detected the bank 1 IMRC actuator is stuck in the open position. Bank 1 refers to the side of the engine with the #1 cylinder, whereas bank 2 refers to the side of the engine with the #2 cylinder. Inline engines, have only one bank – bank 1.

intake manifold

Intake manifold

P2004 symptoms

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Common causes of P2004

Code P2004 is typically caused by one of the following:

  • A failed IMRC actuator
  • A problem with the intake manifold or linkage
  • Wiring issues

How to diagnose and repair P2004

Perform a preliminary inspection

Sometimes P2004 can pop up in error. Clear the code and see if it returns. If it does, the next step is to perform a visual inspection. A trained eye can check for issues such as broken wires and loose connections. If a problem is found, it should be repaired and the code cleared. If nothing is discovered, check for technical service bulletins (TSBs). TSBs are recommended diagnostic and repair procedures put out by the vehicle manufacturer. Finding a related TSB can greatly reduce diagnostic time.

Check the IMRC operation

A technician will begin diagnosis of this code by checking IMRC actuator operation. The best way to do this is with a diagnostic scan tool. On most vehicles, the actuator can be commanded on and off with a scan tool, while monitoring its position on the screen. If the actuator position doesn’t change when commanded, there is either a problem with the actuator, its linkage or its circuit.

  • Power: typically, one of the wires attached to the IMRC actuator is battery voltage.
  • Ground: one of the wires is ground.
  • Signal: one of the wires is a control signal from the PCM.
  • Return: one of the wires is a return signal to the PCM. This input allows the PCM to know the status of the actuator.

Check the IMRC circuit

Next, the reason for the non-functional IMRC actuator must be determined. Checking the actuator circuit is the first step. In most cases, there are four wires going to the actuator: power, ground, signal and return. A digital multimeter (DMM) is used to check that all four portions of the circuit are working properly.

If a problem is found in the circuit, the factory wiring diagram will need to be traced. Then, once the problem area has been located, the open/short circuit can be repaired.

Check the intake manifold and linkage

If the actuator and its circuitry check out, the manifold and its linkage will need to be inspected. The manifold many need to be removed for this. Once the manifold is off, the butterfly valves can be viewed from the underside. Depending on the design, the butterfly valves may be operated with mechanical linkage or with engine vacuum.

  • Mechanical linkage can be operated by hand to check for proper operation. If it binds or doesn’t open the valves, the linkage or manifold should be replaced.
  • With a vacuum controlled system, the butterfly valves can be opened and closed with a handheld vacuum pump. If the valves don’t operate as designed during this test, the manifold is probably defective.

Note: It’s also a good idea to check the vacuum hoses on system that’s controlled by engine vacuum.

Other diagnostic codes related to P2004

  • P2005: Code P2005 indicates the PCM determined the bank 2 IMRC actuator is stuck in the open position.
  • P2006: Code P2006 indicates the PCM determined the bank 1 IMRC actuator is stuck in the closed position.
  • P2007: Code P2007 indicates the PCM determined the bank 2 IMRC actuator is stuck in the closed position.
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