Manufacturer Code Charts: 1858
Ratio of HFM signal to intake manifold pressure is too low.
Possible cause:
- B28 (Pressure sensor)
- B2/6 (Left hot film mass air flow sensor)
- B2/7 (Right hot film mass air flow sensor)
Affected functions:
- Engine output
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Test 1: Check component B2/6 (Left hot film mass air flow sensor).
Test 2: Check component B2/7 (Right hot film mass air flow sensor).
Test 3: Check component B28 (Pressure sensor).
1. Check component B2/6 (Left hot film mass air flow sensor).
Test 1.1: Check signal of component via actual value with engine speed greater than 3000 rpm.
Test 1.2: Check power supply of component.
Test 1.3: Check signal of component via actual value with engine OFF.
1.1. Check signal of component via actual value with engine speed greater than 3000 rpm.
Warning!Communication with ECU required.
1.2. Check power supply of component.
Test prerequisite
- The actual value is not o.k.
Test sequence
- Switch off ignition.
- Detach coupling at component .
- Measure direct voltage with multimeter between sockets (B2/6) 2 and (B2/6) 1
- Switch on ignition.
Specified value
- Voltage[11.0...15.0] V
Question
- Is the measurement value OK?
YES
The actual value is okay.Further possible causes of fault
- Unmetered air
- Signal wire
- B2/6 (Left hot film mass air flow sensor)
End of test
NO
The measurement value is not OK.Possible cause and remedy
- K40/4f43 (Fuse 43)
- Cable for voltage supply
End of test
1.3. Check signal of component via actual value with engine OFF.
Warning!Communication with ECU required.
2. Check component B2/7 (Right hot film mass air flow sensor).
Test 2.1: Check signal of component via actual value with engine OFF.
Test 2.2: Check signal of component via actual value with engine speed greater than 3000 rpm.
Test 2.3: Check power supply of component.
2.1. Check signal of component via actual value with engine OFF.
Warning!Communication with ECU required.
2.2. Check signal of component via actual value with engine speed greater than 3000 rpm.
Warning!Communication with ECU required.
2.3. Check power supply of component.
Test prerequisite
- The actual value is not o.k.
Test sequence
- Switch off ignition.
- Detach coupling at component .
- Measure direct voltage with multimeter between sockets (B2/7) 2 and (B2/7) 1
- Switch on ignition.
Specified value
- Voltage[11.0...15.0] V
Question
- Is the measurement value OK?
YES
The actual value is okay.Further possible causes of fault
- Unmetered air
- Signal wire
- B2/7 (Right hot film mass air flow sensor)
End of test
NO
The measurement value is not OK.Possible cause and remedy
- K40/4f43 (Fuse 43)
- Cable for voltage supply
End of test
3. Check component B28 (Pressure sensor).
Test 3.1: Check component B28 (Pressure sensor) using actual value.
Test 3.2: Test signal voltage of component B28 (Pressure sensor).
Test 3.3: Check power supply of component B28 (Pressure sensor).
3.1. Check component B28 (Pressure sensor) using actual value.
Test sequence
- Switch on ignition.
Status of relevant actual value:
- Intake manifold pressure (ADC):Warning! Communication with ECU required.
Specified values
- Intake manifold pressure,Ignition ON: > 3.5 V
- Intake manifold pressure,Operate engine at idling speed.:< 2 V
Question
- Is the actual value o.k.?
YES
The actual value is okay.End of test
NO
The actual value is not o.k.Possible cause and remedy
- Check power supply of component B28 (Pressure sensor).
- Test signal voltage of component B28 (Pressure sensor).
Further possible causes of fault
- Vacuum line
3.2. Test signal voltage of component B28 (Pressure sensor).
Figure legend
- A -ConnectionTest cable 35-pin socket box
- 001 -Sockets of component N3/10 (ME-SFI [ME] control unit)
- 05 -35-pin socket box
- 050 -126-pin socket box
- 108 -Test cable 266 589 01 63 00
- N3/10 (ME-SFI [ME] control unit)
- II 1-63ConnectionTest cable
- III 64-126ConnectionTest cable
Warning!
-
- Connection A of test cable 108 may NOT be connected to connection B of the 126-pin socket box (050).
Figure legend
- B28 (Pressure sensor)
- 126/2 -'Secondary air injection right bank of cylinders' shutoff valve
Test prerequisite
- The power supply of component B28 (Pressure sensor) is OK.
Test sequence
- Switch off ignition.
- Connect the vacuum tester to the input of component B28 (Pressure sensor) with the 3 x distributor.
- Connect socket box (126-pin) to component N3/10 (ME-SFI [ME] control unit).
- Measure direct voltage with multimeter between sockets [ M.15 ] 15 and [ M.86 ] 86 of the 126-pole socket box tester.
- Switch on ignition.
Specified values
- Ignition ON: >3.5 V
- Operate engine at idling speed.(Vacuum> 500 mbar):< 2 V
Question
- Are the measurement values OK?
YES
The measurement values are OK.End of test
NO
The measurement values are not OK.Possible cause and remedy
- Lines to component B28 (Pressure sensor)
- B28 (Pressure sensor)
Further possible causes of fault
- Vacuum line
End of test
3.3. Check power supply of component B28 (Pressure sensor).
Figure legend
- B28 (Pressure sensor)
- 126/2 -'Secondary air injection right bank of cylinders' shutoff valve
Test prerequisite
- The actual value is not o.k.
Test sequence
- Switch off ignition.
- Detach coupling at component B28 (Pressure sensor).
- Measure direct voltage with multimeter between sockets (B28) 1 and (B28) 3
- Switch on ignition.
Specified value
- Voltage[4.75...5.25] V
Question
- Is the measurement value OK?
YES
The measurement value is OK.Further possible causes of fault
- Test signal voltage of component B28 (Pressure sensor).
NO
The measurement value is not OK.Possible cause and remedy
- Lines to component N3/10 (ME-SFI [ME] control unit)
End of test