P0237

[1] Charge pressure is too low. [P0237]

Charge pressure is too low.

Test 1: Inspect charge air system for leaks
Test 2: Adaptation M16/7 (Recirculating air flap actuator)
Test 3: Check component B28 (Pressure sensor)
Test 4: Check correct assignment of compressor

1 Inspect charge air system for leaks

Special tool
- Test pressure gauge Charge air 611 589 02 21 00
- Connection adapter 271 589 00 91 00

Figure legend





- 119 Test pressure gauge
- 119/3 Compressed-air line
- 119/4 Plug 'Oil dipstick'
- 119/6 Connection adapter

Test sequence
- Remove air cleaner element.
- Seal guide tube for oil dipstick with stop plug.

Safety note!!:
- Only remove or install the plug when the charge air system is pressureless!
- Connect test pressure gauge. (See fig.)
- Open shutoff cock of tester in direction of flow.
- Turn pressure reducing valve knob SLOWLY to the right until 300 mbar is reached.

IMPORTANT NOTE
- The pressure in the system will build up quite SLOWLY.

Leaks can now be located acoustically or made visible by spraying on leak detector spray.

Question: Was the test o.k.?

No
- The test is not o.k..

Fig. legend/ fig.





- b Air line Secondary air system
- B2/5 (Hot film MAF sensor)
- M16/6 (throttle valve actuator)
- M16/7 (Recirculating air flap actuator)
- 122 Suction damper
- 50 Kompressor
- Pressure damper
- 110/1 Suction pipe
- 110/2 Charge air cooler
- 110/6 Suction/charge line

Possible cause and remedy
- Inspect all the vacuum lines connected to the inlet tract, for leaks and damage, and replace if necessary.

**End of test**

Yes
- The test is o.k..
**End of test**

2 Adaptation M16/7 (Recirculating air flap actuator)

Possible cause and remedy
- Mechanical fault, Inspect intake tract for residues.
- Test cables
- N3/10 (ME-SFI control module)

**End of test**

3 Check component B28 (Pressure sensor)

Test 3a: Check actual value B28 (Pressure sensor)
Test 3b: Test voltage supply of component B28 (Pressure sensor)
Test 3c: Test signal voltage of component B28 (Pressure sensor)

3a Check actual value B28 (Pressure sensor)

Test prerequisite
- Coolant temperature > 80°C

Test sequence
- Engine at idle speed

Status of relevant actual value:
- Temperature of coolant: Communication with ECU required
- Intake manifold pressure: Communication with ECU required
- Altitude pressure: Communication with ECU required

Specified value
- Intake manifold pressure ca. [250 ... 400] hPa
- Altitude pressure ca. [950 ... 1100] hPa

Question: Is the actual value o.k.?

3b Test voltage supply of component B28 (Pressure sensor)

Test prerequisite
- The actual value is not o.k.

Test sequence
- Switch off ignition.
- Connect test wiring harness with socket box to component N3/10 (ME-SFI control module).
- [M.57] 57<-->68 [M.68]
- Switch on ignition

Specified value
- Voltage [4.8 ... 5.2] V

Question: Is the measured value okay?

No
The measured value is not o.k.
Possible cause and remedy
- Cable for voltage supply
- N3/10 (ME-SFI control module)
**End of test**

Yes
- The measured value is o.k.
Possible cause and remedy
- Signal wire
- B28 (Pressure sensor)
**End of test**

3c Test signal voltage of component B28 (Pressure sensor)

Figure legend





- 019 Vacuum tester

Test prerequisite
- The voltage supply of the component B28 (Pressure sensor) is o.k.

Test sequence
- Switch off ignition.
- Connect vacuum tester to intake manifold using 3-way distributor.
- Connect test wiring harness with socket box to component N3/10 (ME-SFI control module).
- [M.33] 33<-->27 [M.27]

Specified values
- Ignition ON: > 3.5 V
- Operate engine at idling speed.(Vacuum> 500 mbar): < 2 V

Question: Are the measured values okay?

No
- The measured values are not o.k.
Possible cause and remedy
- Leads to component B28 (Pressure sensor)
- B28 (Pressure sensor)
Further possible causes of fault
- Vacuum line
**End of test**

Yes
- The measured values are o.k.
**End of test**

4 Check correct assignment of compressor

Possible cause and remedy:
- Inspect belt pulley for color and diameter.

Engine version: 1 105/120SW
- Engine: 271.940, 271.941, 271.942, 271.943, 271.944, 271.945, 271.946, 271.947
- Color: White marking
- Diameter: 72 mm

Engine version: 2 140SW
- Engine: 271.948 271.949
- Color: Green marking
- Diameter: 66 mm
**End of test**