2010 Mercedes Benz C 300 (204.054) V6-3.0L (272.947) Page 754

Lambda control, before TWC right : Lambda control is at lean stop. (P0172)

Possible cause:

- Lambda control is at rich stop.

Affected functions:

- Engine output

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Test 1: Check self-adaptation.

1. Check self-adaptation.

Test 1.1: Lambda control is at rich stop.

1.1. Lambda control is at rich stop.

Test 1.1.1: Check signal from component B2/5 (Hot film mass air flow sensor) via actual value.

Test 1.1.2: Check seal of component B2/5 (Hot film mass air flow sensor) with air filter for cracks.

Test 1.1.3: Test fuel pressure and delivery of component M3 (Fuel pump).

Test 1.1.4: Test gasoline fuel for water and diesel portions.

Test 1.1.5: Inspect the intake system of the engine for leaks.

Test 1.1.6: Check exhaust system for leaks.

1.1.1. Check signal from component B2/5 (Hot film mass air flow sensor) via actual value.

Test 1.1.1.1: Check signal of component B2/5 (Hot film mass air flow sensor) via actual value with engine speed greater than 3500 rpm.

Test 1.1.1.2: Check reference signal of component B2/5 (Hot film mass air flow sensor).

Test 1.1.1.3: Check signal of component B2/5 (Hot film mass air flow sensor) via actual value with engine OFF.

1.1.1.1. Check signal of component B2/5 (Hot film mass air flow sensor) via actual value with engine speed greater than 3500 rpm.

Warning!Communication with ECU required.

1.1.1.2. Check reference signal of component B2/5 (Hot film mass air flow sensor).

Test sequence

- Switch on ignition.

Status of relevant actual value:

- HFM-SFI ( Reference signal ):Warning! Communication with ECU required.

Specified value

- Reference signal[46...59] ms

Question

- Is the measurement value OK?

YES

The actual value is okay.End of test

NO

The actual value is not o.k.Possible cause and remedy

- Check lines from component N3/10 (ME-SFI [ME] control unit) to component B2/5 (Hot film mass air flow sensor).

- B2/5 (Hot film mass air flow sensor)