Intake Manifold Tuning Valve, Checking

Intake Manifold Tuning Valve, Checking

Special tools, testers and auxiliary items required

• multimeter.

• Wiring diagram.

Test requirements

• The Intake Manifold Tuning (IMT) Valve (N156) fuse OK.

• The Motronic Engine Control Module (ECM) Power Supply Relay (J271) fuse OK.

• Battery voltage at least 12.5 V.

• All electrical consumers switched off (radiator fan must NOT run during test).

• A/C switched off.

• The ignition switched off.

Test procedure

- Perform a preliminary check to verify the customers complaint. Refer to => [ Preliminary Check ] Preliminary Check.

Start diagnosis

• Voltage is supplied to the Intake Manifold Tuning (IMT) Valve (N156) from the Motronic Engine Control Module (ECM) Power Supply Relay (J271).

Procedure

- Disconnect the Intake Manifold Tuning (IMT) Valve (N156) electrical harness connector - 4 -.





Checking internal resistance

- Using a multimeter, check the Intake Manifold Tuning (IMT) Valve (N156) terminals 1 to 2 for resistance.

Specified value: 25 to 35 ohms (at approx. 20 °C)

If the specified value was not obtained:

- Replace the Intake Manifold Tuning (IMT) Valve (N156).

If the specified value was obtained:

Checking voltage supply

Switch the ignition on.

- Using a multimeter, check the Intake Manifold Tuning (IMT) Valve (N156) electrical connector terminal 2 to Ground (GND) for voltage.





Specified value: battery voltage.

Switch the ignition off.

If the specified value was not obtained:

- Check the wiring from the Intake Manifold Tuning (IMT) Valve (N156) electrical connector terminal 2 to the fuse SA15 for a open circuit.

- Check the electrical harness connector for damage, corrosion, loose or broken terminals.

- If necessary, repair the wiring connection.

If no malfunctions are found in the wiring:

Checking wiring

If the manufacturers test box is being used, perform the following step.

- Install the test box.

If the manufacturers test box is not being used, perform the following step.

- Remove the Motronic Engine Control Module (ECM) (J623). Refer to => [ Engine Control Module, Replacing ] Engine Control Module, Replacing.

- Using a multimeter, check the Intake Manifold Tuning (IMT) Valve (N156) electrical harness connector terminal 1 to the Motronic Engine Control Module (ECM) (J623) electrical harness connector T40 terminal 121 for an open circuit.









Specified value: 1.5 ohms Max.

If the specification was not obtained:

- Check the wiring for a short circuit to Battery (+), or an open circuit.

- Check the electrical harness connector for damage, corrosion, loose or broken terminals.

- If necessary, repair the faulty wiring connection.

If no malfunction is detected in the wiring:

- Replace the Motronic Engine Control Module (ECM) (J623) => [ Engine Control Module, Replacing ] Engine Control Module, Replacing.

Final procedures

After the repair work, the following work steps must be performed in the following sequence:

1. Check the DTC memory. Refer to => [ Diagnostic Mode 03 - Read DTC Memory ] Diagnostic Mode 03 - Read DTC Memory.

2. If necessary, erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Mode 04 - Erase DTC Memory.

3. If the DTC memory was erased, generate readiness code. Refer to => [ Readiness Code ] Readiness Code.