Fuel Pressure Regulator Valve, Checking

Special tools and workshop equipment required 

• multimeter.
• Wiring diagram.

Test requirements 

• The Engine Component Power Supply Relay -J757- OK.
• The Motronic Engine Control Module (ECM) - J623- fuses OK.
• The fuel filter OK.
• The battery voltage at least 12.5 V.
• All electrical consumers switched off (radiator fan must NOT run during test).
• A/C switched off.
• The fuel tank at least ¹ /₄ filled.
• The ignition switched off.

Test procedure 

-- Perform a preliminary check to verify the customers complaint. Refer to PRELIMINARY CHECK.

Start diagnosis 

-- Remove the engine cover with air filter. Refer to appropriate Service Information.

Checking resistance 

-- Disconnect the Fuel Pressure Regulator Valve -N276- electrical harness connector -2-.

-- Using a multimeter, check the Fuel Pressure Regulator Valve -N276- terminals 1 to 2 for resistance.

Specified value: 25 to 35 Ω (at Approx. 20° C).

If the specified value was not obtained:

-- Replace the Fuel Pressure Regulator Valve -N276-. Refer to appropriate Service Information.

If the specified value was obtained:

Checking voltage 

Switch the ignition on.

-- Using a multimeter, check the Fuel Pressure Regulator Valve -N276- electrical connector terminal 1 to Ground (GND) for voltage.

Specified value: battery voltage.

If the specified value was not obtained:

-- Check the wiring from the Fuel Pressure Regulator Valve -N276- electrical connector terminal 1 to the Engine Component Power Supply Relay -J757- terminal 8 for a short circuit to Ground (GND), or an open circuit.

Switch the ignition off.

-- 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 appropriate Service Information.

-- Using a multimeter, check the Fuel Pressure Regulator Valve -N276- electrical harness connector terminals to the Motronic Engine Control Module (ECM) -J623- electrical harness connector T60 terminals for an open circuit according to the appropriate System Wiring Diagram.

Fuel Pressure Regulator Valve -N276- electrical harness connector terminal	Motronic Engine Control Module (ECM) -J623- electrical connector T60 terminal or test box socket
2	15

Specified value: 1.5 Ω 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-. Refer to appropriate Service Information.

-- Install the engine cover with air filter. Refer to appropriate Service Information.

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.
2. If necessary, erase the DTC memory. Refer to DIAGNOSTIC MODE 04 - ERASE DTC MEMORY.
3. If the DTC memory was erased, generate readiness code. Refer to READINESS CODE.