Symptoms
Symptoms of a P2018 engine code may include:
- Malfunction Indicator Lamp (MIL) illuminated
- Lack of power
- Occasional misfires
- Poor fuel economy
Causes
Typically, the causes for this code to set are as follows:
- Sticky/faulty throttle plates/body
- Sticky/faulty IMRC valve
- Faulty IMRC actuator/sensor
- Rarely – Faulty Powertrain Control Module (PCM)
- (Programming required after replacement)
Diagnostic Steps
and Repair Information
A good starting point is always to check the Technical Service Bulletins (TSBs) for your specific vehicle. Your issue might be a known problem with a known fix released by the manufacturer and could save you time and money during diagnosis.
The most common failure items (and the most often misdiagnosed items) on these systems are: the IMRC vacuum solenoids, as carbon builds up inside the vent portion and prevents them from venting properly at all, and the second is that the IMRC plates stick/bind due to carbon deposits around them.
First, note if there are any other Diagnostic Trouble Codes. If any are related to the intake/engine performance system, diagnose those first. Misdiagnosis is known to occur if a technician diagnoses this code before any intake/engine performance-related system codes have been thoroughly diagnosed and dismissed. Ensure there are no intake or exhaust leaks. An intake leak, or vacuum leak, causes the engine to idle roughly. An exhaust leak makes the engine appear to be running lean according to the Air/Fuel Ratio (AFR) or Oxygen (O2) sensor.
The next step in this process is to locate the IMRC valve/sensor on your specific vehicle. Once located, visually inspect the connectors and wiring. Look for chafing, scraping, bare wires, worn spots, or melted plastic connectors. Disconnect the connectors and carefully inspect the terminals (the metal parts) inside the connectors. Check that they are not burnt or corroded. If in doubt, obtain an electrical contact cleaner from any auto parts store if terminal cleaning is needed. If not available, get some rubbing alcohol and a small plastic-bristled brush (a used toothbrush) to clean them. Once cleaned, let them air dry. Pack the connector cavity with a dielectric silicone compound (the same type used for bulb sockets and spark plug wires) and reassemble.
If you have a scan tool, clear the Diagnostic Trouble Codes from memory and see if this code returns. If not, the connections were likely your issue.
If the code returns, we will need to test the voltage signals of the IMRC valve/sensor to and from the PCM. Monitor the IMRC sensor voltage on your scan tool. If no scan tool is available, test the signal from the IMRC sensor with a Digital Volt-Ohm Meter (DVOM). With the sensor connected, the red voltmeter lead should be attached to the IMRC sensor signal wire and the black voltmeter lead connected to ground. Start the engine and monitor the IMRC sensor input. Snap the throttle. As the engine RPM increases, the IMRC sensor signal should change. Check the manufacturer’s specifications, as there may be a chart informing you of the voltage at a given RPM.
If it fails this test, you will need to verify that the IMRC valve will move and is not stuck or binding inside the intake manifold. Remove the IMRC sensor/actuator and grasp the pin or linkage that moves the plates/valves inside the intake manifold. Keep in mind that these may have a strong return spring, so there might be tension when you turn them. Check if the plates/valves are stuck/loose when you turn them. If so, you will need to replace them, and this usually means you will have to replace the entire intake manifold. It is best to leave this task to professionals.
If the IMRC plates/valves turn without any binding or excessive looseness, this would indicate the need to replace the IMRC sensor/actuator and retest.
Again, it cannot be stressed enough that all other codes should be diagnosed before this one, as issues causing other codes to set can also cause this one. It cannot be overemphasized that once the first or first couple of diagnostic steps are performed and the problem is not obvious, it would be wise to consult an automotive professional regarding the repair of your vehicle, as most repairs from that point forward will require the removal and replacement of the intake manifold in order to properly fix this code and the related engine performance issue.