For 1990-2009 cars
Engine Controls Components
Cell 20: EVAP, Air Injection and Intake Resonance Controls
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

### Circuit Description

The Catera Multi-Ram System uses variable air induction tuning in order to achieve maximum performance and efficiency over the entire operating range of the engine. The system consists of two main parts. The intake manifold contains the Intake Plenum Switchover valve. This vacuum operated valve is essentially a moveable divider that changes the airflow characteristics of the intake manifold. Vacuum to the valve is controlled by an ECM controlled solenoid valve. The second part is the Intake Resonance Switchover valve. This vacuum operated valve is located in the air intake duct assembly in front of the engine. This is also basically a moveable divider that changes the tuning of the air intake system. Vacuum to the valve is controlled by an ECM controlled solenoid valve. By opening and closing these valves independently, in different combinations, four different air flow configurations can be created, each optimized to a particular set of engine operating conditions.

Both solenoid valves are supplied power via the Main relay (Switched B+). Both solenoid valves have a control circuit to the Engine Control Module (ECM). The ECM controls a valve by grounding the control circuit via an internal solid state device called a driver. The primary function of the driver is to supply the ground for the component being controlled. Each driver has a fault line which is monitored by the ECM. When the ECM is commanding a component on, the voltage of the control circuit should be low (near 0 volts). When the ECM is commanding the control circuit to a component off, the voltage potential of the circuit should be high (near the battery voltage). If a problem is detected with either of the solenoid valve control circuits, a DTC will set. If either of the following DTCs are set, perform the DTC table before running this diagnostic:

• | DTC P1112 -- Intake Plenum Switchover Valve Control

• | DTC P1113 -- Intake Resonance Switchover Valve Control

### Diagnostic Aids

Visually inspect the system. Check and repair the following conditions as necessary:

• | Check for any disconnected or damaged vacuum hoses/components.

• | Check the linkage between the vacuum actuators and the valves. Move the linkage by hand. Check for binding, or any interference with the hoses, the wiring or any other components.

### Test Description

The number(s) below refer to step numbers on the diagnostic table.

1. The solenoid valve control circuits must be diagnosed first, if DTC P1112 or P1113 is set.

#### Multi-Ram System Diagnosis

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 | Is DTC P1112 or P1113 set? | -- | Go to the applicable DTC | Go to Step 3
3 |

1. Visually inspect the system.
2. Check for the following conditions and repair as necessary:

• | Check for any disconnected or damaged vacuum hoses/components.

• | Check the linkage between the vacuum actuators and the valves. Move the linkage by hand. Check for binding, or interference with the hoses, the wiring or any other components.

Was a problem found?

--

Go to Step 15

Go to Step 4

4 |

1. Start the engine.
2. Observe the vacuum actuator linkages for the Intake Plenum Switchover valve and the Intake Resonance Switchover valve.
3. Command each valve on and off with a scan tool.

Do both valves operate?

--

Go to Step 5

Go to Step 6

5 |

1. Turn off the ignition.
2. Remove the duct between the Intake Resonance Switchover valve and the throttle body.
3. Hold the throttle blades open in order to view the moveable divider in the back of the intake manifold. Move the actuator linkage by hand and check that the divider moves with the linkage.
4. Look down the passages in the Intake Resonance Switchover valve in order to view the moveable divider between the two sides of the valve.
5. Move the actuator linkage by hand . Then, check to be sure that the divider moves with the linkage.

Do both valves operate properly?

--

No trouble found

Go to Step 14

6 | The remainder of the table applies to the valve(s) that did not operate.

1. Use the scan tool in order to exit the device control.
2. Disconnect the manifold vacuum supply hose at the solenoid valve while observing the actuator linkage.

Does the actuator move when the vacuum is disconnected?

--

Go to Step 10

Go to Step 7

7 | Is a vacuum present on the manifold vacuum supply hose? | -- | Go to Step 8 | Go to Step 11
8 | Disconnect the other hose from the solenoid valve. Then, connect the hoses together by using a suitable vacuum connector. Does the actuator linkage operate? | -- | Go to Step 10 | Go to Step 9
9 | Disconnect the vacuum hose from the actuator. Is a vacuum present? | -- | Go to Step 13 | Go to Step 12
10 | Replace the solenoid valve. Is the action complete? | -- | Go to Step 15 | --
11 | Repair the vacuum supply hose or the plugged vacuum source. Is the action complete? | -- | Go to Step 15 | --
12 | Repair the vacuum hose to the actuator. Is the action complete? | -- | Go to Step 15 | --
13 | Replace the valve/actuator assembly. Is the action complete? | -- | Go to Step 15 | --
14 | Replace the affected valve/actuator assembly. Is the action complete? | -- | Go to Step 15 | --
15 |

1. Start the engine.
2. Observe the vacuum actuator linkages for the Intake Plenum Switchover valve and the Intake Resonance Switchover valve.
3. Command each valve on and off with a scan tool.

Do both valves operate?

--

The System is OK

Go to Step 2