Positive Crankcase Ventilation (PCV) Heating Element N79, Checking

Positive Crankcase Ventilation (PCV) Heating Element N79, Checking

NOTE: Use only gold-plated terminals when servicing terminals in the electrical harness connector of Positive Crankcase Ventilation (PCV) Heating Element N79.

Special tools, testers and auxiliary items required
- Multimeter.
- Wiring diagram.

Test requirements
- The Motronic Engine Control Module (ECM) J623 fuses OK.







- The Power Supply Relay (terminal 50) J682 OK.
- Battery voltage at least 12.5 volts.
- All electrical consumers such as, lights and rear window defroster, switched off.
- Vehicles with automatic transmission, shift selector lever into position "P" or "N".
- A/C switched off.
- Ground (GND) connections between engine/transmission/chassis OK.
- Ignition switched off.
- Engine cold.

Test procedure
- Perform a preliminary check to verify the customers complaint. Preliminary Check

Start diagnosis

Checking internal resistance







- Disconnect the Positive Crankcase Ventilation (PCV) Heating Element N79 electrical harness connector - 2 -.







- Using a multimeter, check the Positive Crankcase Ventilation (PCV) Heating Element N79 terminals 1 to 2 for resistance.
- Specified value: 25 to 35 Ohms (at approx. 20 degrees C)

If the specified value was not obtained:
- Replace the Positive Crankcase Ventilation (PCV) Heating Element N79 Engine Mechanical, Fuel Injection Ignition.

If the specified value was obtained:

Checking voltage
Switch the ignition on.







- Using a multimeter, check the Positive Crankcase Ventilation (PCV) Heating Element N79 electrical connector terminal 1 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 Positive Crankcase Ventilation (PCV) Heating Element N79 electrical connector terminal 1 to the Power Supply Relay (terminal 50) J682 socket 1/30 for a short circuit to Ground (GND), or an 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 Ground (GND)







- Using a multimeter, check the Positive Crankcase Ventilation (PCV) Heating Element N79 electrical connector terminal 2 to Ground (GND) for resistance.

Specified value: 1.5 Ohms Max.

If the specification was not obtained:
- Check the wiring for a short circuit to each other, Battery (+), and Ground (GND).
- Check the electrical harness connector for damage, corrosion, loose or broken terminals.
- If necessary, repair the faulty wiring connection.
- Erase the DTC memory. Diagnostic Modes 01 - 09.
- Perform a road test to verify repair.

If the DTC does not return:
Repair complete, Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes
- End diagnosis.

If the DTC does return and no malfunction is detected in the wiring and the voltage supply was OK:
- Replace the Motronic Engine Control Module (ECM) J623.
- Assembly is performed in the reverse of the removal.

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

1. Check the DTC memory. Diagnostic Modes 01 - 09
2. If necessary, erase the DTC memory. Diagnostic Modes 01 - 09
3. If the DTC memory was erased, generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes

End of Diagnosis