Fuel Pressure Regulator Valve, Checking

Special Tools And Workshop Equipment Required 

• Multimeter.
• Wiring diagram.

Test Requirements 

• The Fuel Pump (FP) Control Module -J538- 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 the appropriate Service Information.

Checking resistance

-- Disconnect the Fuel Pressure Regulator Valve -N276- electrical harness connector -2- from the Fuel High Pressure Pump -- assembly -1-.

-- 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 the 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 for voltage.

Specified value: Battery voltage.

Switch the ignition OFF.

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 2 (relay pin 87) for a short circuit to Ground, high resistance or an open circuit.

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

-- If necessary, repair the wiring connection.

-- If a short was found, replace fuse 20 in fuse Panel B

If the specified value was obtained:

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 the 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 terminals for an open circuit according to the chart below.

Fuel Pressure Regulator Valve -N276- electrical harness connector terminal	Motronic Engine Control Module (ECM) -J623- electrical connector T60 terminal or test box socket
2	19

Specified value: 1.5 Ω Max.

If the specified value was Not obtained:

-- Check the wiring for an open, high resistance or short to ground.

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

-- If necessary, repair the faulty wiring connection.

If the specified value was obtained:

-- Replace the Motronic Engine Control Module (ECM) -J623-. Refer to the appropriate Service Information.

-- Install the engine cover with air filter. Refer to the 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 .