GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2001 🢒 Catera 🢒 Engine 🢒 Engine Controls - 3.0L (L81) 🢒 Intake Manifold Runner Control System Diagnosis

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 plenum switchover valve and the intake resonance switchover valve. The engine control module (ECM) controls two solenoids that apply vacuum to each of the valve actuators. When the ECM commands the solenoid ON, vacuum is supplied to that actuator, causing the valve to open or close. Vacuum is supplied to each of the solenoids from a vacuum reservoir located near the intake air duct. The reservoir is required to maintain the vacuum supply during extended acceleration conditions. The intake manifold contains the intake plenum switchover valve. This vacuum operated valve is a moveable divider that changes the airflow characteristics of the intake manifold. The second part of the multi-ram system is the intake resonance switchover valve. This vacuum operated valve is located in the air intake duct assembly. This is a moveable divider that changes the tuning of the air intake system. By opening and closing these valves independently, in different combinations, four different air flow configurations can be created, each optimizing a set of engine operating conditions.

Both solenoid valves are supplied switched battery power from the engine controls power relay. Both solenoid valves have a control circuit to the ECM. The ECM controls a valve by grounding the control circuit. If a fault is detected with either of the solenoid valve control circuits, a diagnostic trouble code (DTC) will set.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

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

    2.

  2. This step is to confirm that the valve inside the housing is moving correctly and is not loose or damaged in any way.

Step

Action

Values

Yes

No

1

Did you perform the Diagnostic System Check-Engine Controls?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

Is DTC P1112 or P1113 set?

--

Go to DTC P1112 or DTC P1113

Go to Step 3

3

Visually inspect the system for the following conditions and repair as necessary:

    • Inspect for any disconnected or damaged vacuum hoses and components. Refer to Emission Hose Routing Diagram .
    • Inspect 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.

Did you find and correct the condition?

--

Go to Step 13

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 solenoid 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. Move the actuator linkage at the rear of the intake plenum by hand and listen for confirmation that the divider is moving freely in the plenum. If a problem is suspected with the valve, refer to Intake Plenum Switchover Valve Replacement for further inspection.
  4. Look down the passages in the intake resonance switchover valve in order to view the moveable divider between the two sides of the intake air duct.
  5. Move the actuator linkage by hand. Then ensure that the divider moves with the linkage.

Do both valves operate properly?

--

System OK

Go to Step 12

6
  1. Turn OFF the ignition.
  2. Disconnect the vacuum supply hose at each of the actuators.
  3. Start and idle the engine..
  4. Test for vacuum at each of the actuators.

Is vacuum present at either actuator?

--

Go to Step 11

Go to Step 7

7
  1. With a scan tool, command each of the solenoids ON.
  2. Measure the vacuum at each of the actuators while the respective solenoid is commanded ON.

Is the vacuum above the specified value?

33 kPa (10 in Hg)

Go to Step 12

Go to Step 8

8
  1. Turn OFF the ignition.
  2. Disconnect the vacuum supply hose from the solenoid that did not have vacuum at the actuator.
  3. Start and idle the engine.
  4. Measure the vacuum at the supply hose.

Is the vacuum above the specified value?

33 kPa (10 in Hg)

Go to Step 9

Go to Step 10

9
  1. Turn OFF the ignition.
  2. Inspect the vacuum hose from the solenoid to the actuator for a leak or a restriction.
  3. Repair or replace the hose as necessary.

Did you find and correct the condition?

--

Go to Step 13

Go to Step 11

10

Repair the leak or restriction in one of the following components of the vacuum supply system:

    • Vacuum hose from the reservoir to the solenoids
    • Reservoir
    • Vacuum hose from the intake manifold to the reservoir.

Did you complete the repair?

--

Go to Step 13

--

11

Replace the affected solenoid. Refer to Intake Plenum Switchover Solenoid Replacement or Intake Resonance Switchover Solenoid Replacement .

Did you complete the replacement?

--

Go to Step 13

--

12

Replace the affected valve actuator assembly. Refer to Intake Plenum Switchover Valve Replacement or Intake Resonance Switchover Valve Replacement .

Did you complete the replacement?

--

Go to Step 13

--

13
  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?

--

System OK

Go to Step 2