|Code||Fault Location||Probable Cause|
|P2008|| Intake manifold air control actuator / solenoid, bank 1 -open circuit |
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|Wiring open circuit, intake manifold air control actuator / solenoid|
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What Does Code P2008 Mean?
OBD II fault code P2008 is a generic code that is most commonly defined as “Intake manifold air control actuator / solenoid, Bank 1 -open circuit”, but sometimes also as “Intake Manifold Runner Control (IMRC) Solenoid Control Circuit –Bank 1”, or less often as “Intake Manifold Runner Control Circuit/Open Bank 1”. Note that despite the differences in wording, all three definitions mean the same thing, which is that an open circuit exists in the control solenoid/actuator of the Intake Manifold Runner system. “Bank 1” refers to the bank of cylinders that contains cylinder #1 on engines with two cylinder heads.
Manifold runners have the purpose of increasing, or decreasing the velocity at which the intake air passes through the inlet manifold. In simple terms, a manifold runner is an adjustable flap in each manifold runner that can be adjusted via an actuator, with the degree of opening depending on the engine speed and other operating conditions such as the throttle position, rate of throttle plate movement, and environmental factors such as the barometric pressure and ambient temperature.
During low-speed driving, generally below 3 000 RPM, the engine does not require a large volume of air, and under these conditions, the runner flaps close off about 60% or so of the intake port. This partial restriction increases the flow rate of the air charge, which when the PCM makes suitable adjustments to the fuel delivery, is roughly analogous to the effect that forced induction has.
Conversely, when the engine requires a large volume of intake air, the PCM opens the runner flaps to allow more air to pass into the engine. In a fully functional system, the opening and closing of the runner flaps has the overall effect of increasing performance without using a commensurately larger volume of fuel. This is particularly true of small-capacity engines, although manifold runner flaps are increasingly being used on large capacity engines as well.
However, for the system to work as intended, a high degree of control is required and while this is relatively easily accomplished on systems that use stepper motors as actuators, vacuum operated systems are prone to malfunctions caused by vacuum leaks in both vacuum lines and the vacuum actuator. Nonetheless, it should be noted that while code P2008 is mostly concerned with electrical open circuits in the actuators’ control circuit, vacuum leaks can also cause this code on some applications, since under these conditions the runner flaps’ position sensor can produce a signal that does not agree with the runner flaps’ desired position.
Note that while some applications will store a code and illuminate warning light on the first failure cycles, it is more common for several failure cycles to occur before a warning light will be illuminated on most applications.
The image below shows the typical arrangement of the runner flaps in an inlet manifold. Note the position of the individual flaps that are in the fully open position. Note also the vacuum operated actuator and its integrated position sensor attached to the side of the manifold.
What are the common causes of code P2008?
Common causes of code P2008 could include the following-
- Burnt, damaged, shorted, disconnected, or corroded wiring and/or connectors
- Defective actuator stepper motor
- Vacuum leaks caused by damaged or dislodged vacuum lines and/or vacuum components. Note that vacuum leaks will not necessarily cause this code on all applications that use vacuum control for the manifold runner flaps
- Defective manifold runner position switch
- Failed or failing PCM. Note that this is a rare event, and the fault must be sought elsewhere before any controller is replaced
What are the symptoms of code P2008?
While some applications will not exhibit any symptoms other than a stored trouble code and an illuminated warning light, most other applications will suffer from some driveability issues when the manifold runner flap control system fails. Some common symptoms could include the following, but note that the severity of some symptoms may vary between applications-
- Some applications may experience some power loss at low engine speeds
- Idling may be rough, erratic, or the idling speed may fluctuate
- Some applications may experience some hesitation and stumbling upon acceleration
- Hard or no start conditions may develop on some applications
How do you troubleshoot code P2008?
NOTE: On applications where the manifold runners are controlled with engine vacuum, a hand-held vacuum pump fitted with a graduated gauge will be most helpful in diagnosing and resolving this code.
Record all fault codes, as well as all available freeze frame data. This information can be of use should an intermittent fault be diagnosed later on.
NOTE: It is common for several other engine management codes to be present along with P2008. Therefore, it is important to note all codes, as well as whether they follow or precede P2008. Codes that precede P2008 have likely contributed to P2008, which means that these codes must be investigated and resolved before an attempt is made to diagnose P2008. Failure to do this will almost certainly result in a misdiagnosis, wasted time, and the unnecessary replacement of parts and components.
Refer to the manual for the application to locate and identify the runner control flap actuator, as well as all associated wiring and vacuum lines if the system is vacuum-controlled. Also, use this opportunity to determine the color-coding, routing, and function of each wire in the control circuit.
Once all components/wiring, and vacuum lines are identified, perform a thorough visual inspection of all wiring and lines. Look for damaged, burnt, disconnected, or corroded wiring and/or connectors. Make repairs as required.
If the system is vacuum operated, inspect all vacuum lines for signs of cracking, splitting, hardening, or perforations. Also, check that all connections are tight, that all vacuum check valves allow airflow only in the indicated direction, and that no unmetered air enters the engine, a condition that is usually indicated by a dedicated code. Make repairs as required, but bear in mind that replacing damaged vacuum lines/components is always preferable to making repairs.
Clear all codes after repairs are complete, and operate the vehicle normally before rescanning the system to see if the code returns.
If the code persists but no visible damage to wiring is found, prepare to perform resistance, ground, reference voltage, and continuity tests on all associated wiring, but be sure to disconnect the system from the PCM to prevent damage to the controller during testing.
Compare all obtained readings with the values stated in the manual, and replace or repair wiring as required to ensure that all electrical values fall within the ranges specified by the manufacturer.
NOTE: If the system is vacuum operated, attach the vacuum pump to the point on the actuator where the engine vacuum normally attaches. Draw a progressively deeper vacuum, while monitoring the signal from the position sensor on the scanner. The object of this test is to both determine whether the actuator reacts to a vacuum or not, and to verify that the position sensor is signalling the actual position of the runner flaps to the PCM.
Refer to the manual to determine the value (in Volts) the scanner should display when the runner flaps are fully extended, and compare this with the actual reading on the scanner. If the two values do not agree, suspect either a faulty position switch, or defective vacuum actuator, or a mechanical failure of the runner flaps themselves.
Test the position switch as per the instructions provided in the manual, and replace the switch with an OEM part if it does not conform to the manufacturers’ specifications. Clear all codes after repairs are complete, and operate the vehicle normally before rescanning the system to see if the code returns.
Monitor the vacuum actuator while maintaining a vacuum on it. If vacuum decays, however slowly and it is certain that the test equipment is not defective in any way, the actuator is defective, and it must be replaced with an OEM part to ensure proper operation. Clear all codes after repairs are complete, and operate the vehicle normally before rescanning the system to see if the code returns.
If the fault persists on an electrically operated system, use the scanner to command the flaps fully open from the fully closed position multiple times to check for an intermittent condition. The displayed signal voltage should always be the same in both the fully open, and fully closed positions, regardless of how many times the system is activated with the scanner.
If these values deviate, perform a wiggle test on all connectors while activating the system. If the displayed value(s) change at any point while any given connector is wiggled about, that connector is defective, and must be repaired or replaced. Note that poor electrical connections across connectors are a common cause of open circuits, so pay particular attention to the quality of all electrical connections in this system- or for that matter, any other electrical system that is being tested. Clear all codes after repairs are complete, and operate the vehicle normally before rescanning the system to see if the code returns.
NOTE: Mechanical failure of the runner flaps themselves is unlikely to produce code P2008 and the most likely codes that will be produced by failures of this type will relate to range or performance issues. Note that range/performance related codes can also be caused on vacuum operated systems when the small air filter fitted to vacuum actuators become dirty or clogged.
The diagnostic/repair steps up to this point will almost certainly have resolved code P2008, but in the unlikely event that the code persists beyond Step 5, suspect a particularly stubborn intermittent fault, or a defective PCM. However, PCM failure is an exceedingly rare event, which leaves an intermittent electrical fault as the most likely cause.
Be aware though that intermittent faults can sometimes be extremely challenging to find and repair, and in some cases, it may be necessary to allow the fault to worsen considerably before an accurate diagnosis and definitive repair can be made.