GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Saturn 🢒 2007 🢒 VUE - AWD 🢒 DTC 🢒 DTC P2646
Table 1: Rocker Arm Actuator System Operation

Circuit Description

The DTC P2646 Intake Rocker Arm Actuator System Stuck Off diagnostic monitors the operation of the rocker arm oil control solenoid. The rocker arm oil control solenoid enables the powertrain control module (PCM) to operate the high speed cam system. The high speed cam system significantly increases valve lift at engine speeds above 4,400 RPM. A second camshaft lobe with a high lift profile is cast into each camshaft, alongside the low/medium speed lobes. Unique rocker arms follow both the high speed and low/medium speed cam lobes. At engine speeds below 4,400 RPM, the low/medium speed cam lobes operate the rocker arms. When the rocker arm oil control solenoid is turned ON between 4,400-6,500 RPM, the rocker arms are operated by the high speed cam lobes. The rocker arm oil control solenoid is energized by a 12-volt signal from the PCM.

The rocker arm oil pressure switch detects oil pressure when oil is flowing through the rocker arm oil supply system. When the rocker arm oil control solenoid is ON, the oil pressure switch opens and the signal circuit to the PCM remains high. A DTC P2646 sets when the signal circuit of the rocker arm oil pressure switch remains low even when engine speed is more than 4,400 RPM. For additional information on the operation of the rocker arm oil control system, refer to Rocker Arm Oil Control System Description .

Rocker Arm Actuator System Operation

Rocker Arm Oil Control Solenoid

Oil Pressure/Flow

Rocker Arm Oil Pressure Switch

On

High

Open

Off

Low

Closed

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P2646 Intake Rocker Arm Actuator System Stuck Off

Conditions for Running the DTC
    • Battery voltage is at least 10.5 volts.
    • The engine coolant temperature (ECT) is at least 10°C (50°F).
    • Engine speed is more than 4,900 RPM.
    • The transmission is not in PARK or NEUTRAL.
    • DTC P2646 runs every time the enable criteria is met and the rocker arm oil control system is active.

Conditions for Setting the DTC
    • The signal circuit of the rocker arm oil pressure switch stays low.
    • The above condition is present for at least 5 seconds.

Action Taken When the DTC Sets
    • The PCM illuminates the malfunction indicator lamp (MIL).
    • The PCM stores the conditions that were present when the DTC set as Freeze Frame data.

Conditions for Clearing the MIL/DTC
    • The PCM turns OFF the MIL on the third consecutive trip cycle during which the diagnostic has been run and the fault condition is no longer present.
    • A DTC clears after 40 consecutive warm-up cycles have occurred without a fault.
    • A DTC can be cleared by using the scan tool Clear DTC Information function.

Test Description

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

  1. The Diagnostic System Check - Vehicle prompts the technician to complete some basic checks and store the Freeze Frame data on the scan tool, if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.

    2.

  2. This step checks for a short to ground in the oil pressure switch signal circuit. A DTC P2647 will set if the signal circuit is not shorted to ground.

    3.

  3. This step checks the operation of the rocker arm oil control solenoid. When commanded ON, oil pressure should increase to at least 392 kPa (56 psi).

    4.

  4. This step tests the operation of the rocker arm oil pressure switch. The oil pressure switch is normally closed to ground with less than 48 kPa (7 psi) of oil pressure. With the oil control solenoid energized oil pressure will open the switch and the scan tool should indicate ON.

    5.

  5. After replacing the PCM, the relationship between the crankshaft position (CKP) sensor and the crankshaft must be re-established. A new minimum throttle position and idle speed must also be established.

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Powertrain Control Module Connector End Views or Engine Controls Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle

2
  1. Turn OFF the ignition.
  2. Disconnect the rocker arm oil control solenoid.
  3. Measure the resistance of the solenoid with a DMM.

Is the resistance within the specified range?

14-30 ohms at 20°C (68°F)

Go to Step 3

Go to Step 10

3

  1. Turn ON the ignition, with the engine OFF.
  2. Leave the rocker arm oil control solenoid disconnected.
  3. Clear any DTCs with the scan tool.
  4. Wait 10 seconds and check for DTCs.

Did a DTC P2647 set?

--

Go to Step 4

Go to Step 8

4

  1. Remove the oil pressure switch.
  2. Install the EN 46332 Oil Pressure Gage Adapter to the engine.
  3. Install the oil pressure gage from the SA9127E Bar Gage Set to the adapter.
  4. Install the oil pressure switch to the adapter.
  5. Start and run the engine until the coolant temperature is 85°C (185°F).
  6. Increase the engine speed to 2,800 RPM.
  7. Command the intake rocker arm actuator solenoid ON with the scan tool. Refer to Scan Tool Output Controls .

Is the oil pressure more than the specified value?

392 kPa (56 psi)

Go to Step 6

Go to Step 5

5
  1. Turn OFF the ignition.
  2. Remove the rocker arm oil control solenoid. Refer to Rocker Arm Oil Control Solenoid Valve Replacement .
  3. Inspect for any of the following conditions:
    4. • A stuck or binding spool valve
    • A restriction or blockage in the oil passages
  4. Repair any condition as necessary.

Did you find and correct a condition?

--

Go to Step 12

Go to Step 9

6

  1. Observe the intake rocker arm actuator oil pressure switch parameter on the scan tool.
  2. Increase the engine speed to 2,800 RPM.
  3. Command the rocker actuator solenoid ON with the scan tool.

Did the oil pressure switch indicate ON when the solenoid was commanded ON?

--

Go to Intermittent Conditions

Go to Step 6

7
  1. Disconnect the electrical connector of the rocker arm oil pressure switch.
  2. Connect a DMM to the signal circuit of the oil pressure switch and ground.
  3. Turn ON the ignition, with the engine OFF.
  4. Measure the DC voltage.

Is the voltage more than the specified value?

6.9 V

Go to Step 10

Go to Step 8

8

  1. Inspect for a short to ground in the signal circuit of the rocker arm oil pressure switch.
  2. Repair as necessary. Refer to Wiring Repairs .

Did you find and correct a condition?

--

Go to Step 12

Go to Step 11

9

Replace the rocker arm oil control solenoid valve. Refer to Rocker Arm Oil Control Solenoid Valve Replacement .

Did you complete the replacement?

--

Go to Step 12

--

10

Replace the rocker arm oil pressure switch. Refer to Rocker Arm Oil Pressure Switch Replacement .

Did you complete the replacement?

--

Go to Step 12

--

11

  1. Replace the powertrain control module (PCM). Refer to Control Module References for replacement, setup, and programming.
  2. Perform the idle learn procedure. Refer to Idle Learn .

Did you complete the replacement?

--

Go to Step 12

--

12
  1. Use the scan tool in order to clear the DTCs.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC run and pass?

--

Go to Step 13

Go to Step 2

13

With a scan tool, observe the stored information, Capture Info.

Does the scan tool display any DTCs that you have not diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List - Vehicle

System OK