Fuel pressure is too low. (P0191)

Fuel pressure is too low. (P0191)
Fuel pressure is too low. (P0191)
Possible cause:
­ B4/15 (Fuel pressure sensor)
­ Fuel system control unit
Affected functions:
­
Engine output
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
Test 1: Signal wire PWM signal Fuel pump
Test 2: Check component B4/15 (Fuel pressure sensor).
1. Signal wire PWM signal Fuel pump
Figure legend
10.52SS
Page 8742010 Mercedes Benz E 63 AMG Sedan (212.077) V8­6.3L (156.985)
Copyright ? 2013, ALLDATA
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Page 875
­ A ­ConnectionTest cable 35­pin socket box
­ 001 ­Sockets of component N3/10 (ME­SFI [ME] control unit)
­ 05 ­35­pin socket box
­ 050 ­126­pin socket box
­ 108 ­Test cable 266 589 01 63 00
­ N3/10 (ME­SFI [ME] control unit)
­ II 1­63ConnectionTest cable
­ III 64­126ConnectionTest cable
Warning!
­
­
Connection A of test cable 108 may NOT be connected to connection B of the 126­pin socket box (050).
Test sequence
­ Switch off ignition.
­ Connect socket box (126­pin) to component N3/10 (ME­SFI [ME] control unit).
­ Measure direct current with multimeter between sockets [F.4] 100 and [F.17] 113 of the 126­pole socket box tester.
­ Switch on ignition.
Specified value
­ Amperage[8...15] mA
Question
­
Is the measurement value OK?
YES
The measurement value is OK.Other possible cause of fault
­
In the event of stored faults with a high fault frequency count or in the event of customer complaints, check lines and connectors
for loose contact and corrosion..
­ B4/15 (Fuel pressure sensor)
End of test
NO
The measurement value is not OK.Possible cause and remedy2010 Mercedes Benz E 63 AMG Sedan (212.077) V8­6.3L (156.985)
Copyright ? 2013, ALLDATA
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Page 876
­ Check lines to components N118/3 (Left fuel pump control unit) and N118/4 (Right fuel pump control unit) as per wiring diagram.
Further possible remedies
­
Read fault memories of the control units N118/3 (Left fuel pump control unit) and N118/4 (Right fuel pump control unit).
2. Check component B4/15 (Fuel pressure sensor).
Test 2.1: Check component B4/15 (Fuel pressure sensor) using actual value.
Test 2.2: Check power supply of component B4/15 (Fuel pressure sensor).
2.1. Check component B4/15 (Fuel pressure sensor) using actual value.
Test prerequisite
­ Relevant fault code exists or there is a complaint.
Test sequence
­ Operate engine at idling speed.
Status of the relevant actual values:
­ Fuel pressure ( Absolute value ):Warning! Communication with ECU required.
­ B4/15 (Fuel pressure sensor) : Specified pressure ( Absolute value ):Warning! Communication with ECU required.
Specified values
­ Fuel pressure=Specified pressure
Question
­
Was the test o.k.?
YES
The test was okay.Possible cause and remedy
­
If the case of stored faults which high fault frequency counter or in the case of customer complaints, inspect electric cables and
connections for loose contact and corrosion.
End of test
NO
The test was not okay.Possible cause and remedy
­ Check power supply of component B4/15 (Fuel pressure sensor).
End of test
2.2. Check power supply of component B4/15 (Fuel pressure sensor).
Test prerequisite
­ The actual value is not o.k.
Test sequence
­ Switch on ignition.
­ Unplug connector of pressure sensor B4/15 (Fuel pressure sensor).
­ Measure direct voltage with multimeter between sockets (B4/15) 1 and (B4/15) 3
Specified values
­ Voltage [4.8 ... 5.3] V
Question
­
Is the measurement value OK?2010 Mercedes Benz E 63 AMG Sedan (212.077) V8­6.3L (156.985)
Copyright ? 2013, ALLDATA
YES
The measurement value is OK.Further possible causes of fault
­ Test signal cable of component B4/15 (Fuel pressure sensor) for Short circuit or open circuit.
­ Inspect plug connections for corrosion, pinched insulation and loose contact.
­ B4/15 (Fuel pressure sensor)
End of test
NO
The measurement value is not OK.Possible cause and remedy
­ Check lines to component B4/15 (Fuel pressure sensor) for discontinuity or short circuit to ground.
­ Inspect plug connections for corrosion, pinched insulation and loose contact.
End of test