ME2.7.2(AMG)
B11/4 (Coolant temperature sensor) , Plausibility (P0125)
Possible cause:
- B11/4 (Coolant temperature sensor)
Affected functions:
- Engine cooling
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Test 1: Check component B11/4 (Coolant temperature sensor).
1. Check component B11/4 (Coolant temperature sensor).
Test 1.1: Check component B11/4 (Coolant temperature sensor) using actual value.
Test 1.2: Check internal resistance of component B11/4 (Coolant temperature sensor).
Test 1.3: Test signal voltage of component B11/4 (Coolant temperature sensor).
1.1. Check component B11/4 (Coolant temperature sensor) using actual value.
Test sequence
- Switch on ignition.
Status of relevant actual value:
- Temperature of coolant:Warning! Communication with ECU required.
Specified value
- If the connection is unplugged at component B11/4 (Coolant temperature sensor), the value is approx. -40° C.
- Bridge pin 1 in pin 2 at the unplugged connection of component B11/4 (Coolant temperature sensor).The value is approx. 170° C.
Question
- Is the actual value o.k.?
YES
The actual value is okay.Further possible causes of fault
- Check internal resistance of component B11/4 (Coolant temperature sensor).
NO
The actual value is not o.k.Possible cause and remedy
- Check lines from component B11/4 (Coolant temperature sensor) to component N3/10 (ME-SFI [ME] control unit).
End of test
1.2. Check internal resistance of component B11/4 (Coolant temperature sensor).
Test prerequisite
- The actual value is not o.k.
Test sequence
- Switch off ignition.
- Measure resistance with multimeter between pins (B11/4) 1 and (B11/4) 2
Specified values
- Resistor(20° C): [2937...3237]ohms
- Resistor(30° C]: [1898...2098]ohms
- Resistor(40° C): [1197...1457]ohms
- Resistor(50° C): [855...945]ohms
- Resistor(60° C): [590...650]ohms
- Resistor(70° C): [420...460]ohms
- Resistor(80° C): [305...335]ohms
- Resistor(90° C): [220...240]ohms
- Resistor(100° C): [160...180]ohms
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
- B11/4 (Coolant temperature sensor)
End of test
1.3. Test signal voltage of component B11/4 (Coolant temperature sensor).
Test prerequisite
- The actual value is not o.k.
Test sequence
- Switch off ignition.
- Connect socket box (126-pin) to component N3/10 (ME-SFI [ME] control unit).
- Measure direct voltage with multimeter between sockets (3.4) 37 and (3.22) 55 of the 126-pole socket box tester.
- Switch on ignition.
Status of relevant actual value:
- Temperature of coolant:Warning! Communication with ECU required.
Specified values
- Voltage(20° C): [3.35...3.42] V
- Voltage(30° C]: [2.85...2.90] V
- Voltage(40° C): [2.34...2.39] V
- Voltage(50° C): [1.88...1.92] V
- Voltage(60° C): [1.47...1.50] V
- Voltage(70° C): [1.14...1.17] V
- Voltage(80° C): [0.88...0.90] V
- Voltage(90° C): [0.68...0.70] V
- Voltage(100° C): [0.52...0.54] 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
- Line from control unit N3/10 (ME-SFI [ME] control unit) to component B11/4 (Coolant temperature sensor)
- B11/4 (Coolant temperature sensor)
End of test