Some vehicles are equipped with special valves that alter the airflow inside the engine to make it more efficient. These are called intake manifold runner controls (IMCR) and they can sometimes fail and create a fault code.
What Does P2004 – “Intake Manifold Runner Control Bank 1 – Stuck Open” Mean?
The IMRC is a simple system that helps your engine run more efficiently. It’s a system that is not present in all vehicles, and it is a very simple system, which makes this code somewhat rare. However, if the part malfunctions, it can cause your gas mileage and engine performance to suffer.
The IMRC is controlled by a solenoid that’s controlled by the PCM, the engine’s brain. The solenoid opens a valve, which means that the valve can either be stuck open or stuck closed. Some vehicles have multiple runners, which the computer will label bank 1, bank 2, etc.
P2004 means that the primary (bank 1) solenoid is stuck open (the valve cannot be closed).
How Serious Is Code P2004?
An intake runner issue is usually not a very serious issue. The two most significant issues are both quality of life problems. You’ll have worse gas mileage, and your car will fail a smog check in states where smog checks are necessary. Basically, your car won’t be running as efficiently as it could be.
However, rarely, the engine efficiency issues can progress into worse issues. This is especially true if your engine is already having other issues like a run-lean condition, so keep an eye out for the following problems.
- If you hear loud metallic noises coming from the engine
- Engine performance issues are preventing you from operating the vehicle in a safe way
The PCM, or whichever management computer your vehicle has, is often linked directly to the solenoid, so there are no sensors directly linked to the runner control circuit. However, the MAP sensor is responsible for monitoring the conditions inside the manifold, which the intake runners directly affect.
- Check engine light will be illuminated
- Gas mileage is suffering
- Engine has occasional performance issues
- Engine sometimes stutters at low RPMs
There are only a handful of reasons an IMRC fault code would be generated. They are ordered here from most likely to least likely.
- The solenoid has worn out
- The runners themselves are binding
- There is an electrical issue
- The MAP sensor is sending faulty information
- The intake manifold or manifold gasket is faulty
Your solution is going to depend largely on which part of the system has failed. You can follow these steps to both diagnose and solve the issue.
Visually Inspect the Component
Locate the IMRC valve and inspect it for damage. Sometimes there will be corrosion or broken wires leading to the solenoid. If you can identify the damage and repair it, or clean the corrosion and reset the connection, that may solve the problem.
Remove the Valve
Removing the valve is not a difficult procedure, but it can be frustrating because they are usually in very tight spaces. You’ll either have to spend a fair bit of time removing parts to get to them, or you’ll have to be very patient as you rotate parts in and out like a child’s puzzle.
Once you have the valve removed, you can try giving it a good clean. That may be sufficient, and it’s a lot nicer on your bank account than replacing them.
Replace the MAP Sensor
If the issue persists after the IMRC module has been replaced, the next thing to do is replace the MAP sensor. MAP sensors are easy to access and usually fairly inexpensive, so it’s good to do it before spending the time to remove the intake manifold.
Do a Smoke Test
A smoke test will tell you if you have an intake manifold issue. You can read about the process here. A broken manifold gasket or other vacuum leaks can cause the IMRC module to fail to operate. However, you will usually have other issues if the manifold is leaking, so it should be your last resort.
Don’t be afraid to take the car to a mechanic if you don’t have the time or tools to perform any of the above steps. A good mechanic can run more advanced diagnostics and can replace the module quickly. The largest expense will be the module itself. They can run upwards of $300, so be prepared to spend $500 if you have to take the car in. Furthermore, if your check engine light is on and you can’t read the code, you can always learn more about OBD scanners here.