Signal Too Low

Signal too low

Checking the function of the fuel pump (FP)




- Ignition on.

Note! It is important that only the ignition is on in order for the heater to start.

- Activate the heater.
Listen for a buzzing sound which indicates that the heater is running.
Check the heater function.

Other information
- Engine coolant heater, test running Component Tests and General Diagnostics





Is the heater working?

Yes - Checking components and wiring

No - Checking components and wiring

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Checking components and wiring
Check the fuel pump (FP) and combustion preheater module (CPM) connectors. Check for contact resistance and oxidation.
Check the cable between combustion preheater module (CPM) terminal #13 and fuel pump (FP) terminal 2. Check for an intermittent open-circuit. Check for an intermittent short-circuit to ground.
Check the cable between combustion preheater module (CPM) terminal #11 and water pump terminal 1. Check for an intermittent open-circuit.
Remedy as necessary.

Other information
- Connecting the breakout box Connecting the Breakout Box
- Signal specification Signal Specification
- Fuel pump auxiliary heater, replacing Service and Repair
- Checking wiring and terminals Checking Wiring And Terminals










Continue - Verification

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Checking components and wiring
Check the fuel pump (FP) and combustion preheater module (CPM) connectors. Check for contact resistance and oxidation. Remedy as necessary Check for damage in particular.
Measure between the overheat protection thermostat terminals using an ohmmeter. The resistance must be approximately 0 ohms.
The overheat protection thermostat must be replaced if the value is not correct.
Check the cable between combustion preheater module (CPM) terminal #13 and fuel pump (FP) terminal 2. Check for an open-circuit. Check for an short-circuit to ground.
Check the cable between combustion preheater module (CPM) terminal #11 and fuel pump terminal 1. Check for an open-circuit.
The fuel pump (FP) must be replaced if no faults are found in the cable.

Note! Diagnostic trouble code (DTC) CEM-5F3B and/or diagnostic trouble code (DTC) CEM-5F3D may also be stored if there is a fault in the power cable.

Remedy as necessary.

Other information
- Connecting the breakout box Connecting the Breakout Box
- Signal specification Signal Specification
- Overheat protection thermostat / flame sensor / engine coolant temperature sensor, replacing Service and Repair
- Fuel pump auxiliary heater, replacing Service and Repair
- Checking wiring and terminals Checking Wiring And Terminals










Continue - Verification

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Verification




Verification

Verification

Hint: After carrying out the repair, check that the fault has been remedied.








- Ignition off
- Reinstall the connectors, components etc.
- Ignition on
- Read off the engine coolant temperature.

Note! It is important that only the ignition is on in order for the heater to start.

- Activate the heater.

Hint: After repair, the voltage of the flame sensor can be checked. The voltage must be a maximum of 1.0 V.

Check the heater function.

Caution! In order for to enable start of the heater itself, the battery voltage must be normal, coolant temperature must be lower than +96 °C and the heater's after-run/stop sequence must be finished. There must also be enough fuel in the tank.

Caution! If the heater or other components are not activated, try closing down the activation window and then starting the activation again with the symbol for VCT2000.

Other information:
- Engine coolant heater, test running Component Tests and General Diagnostics.





Is the heater working?

Yes - VERIFIED

No - VERIFICATION FAILEDPAPER

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VERIFIED - Fault Found

VERIFICATION FAILED - Fault-tracing information

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Fault-tracing information




Information

Fault-tracing information
The fault should have been detected and remedied. As this is not the case fault-tracing has failed.
Exit fault-tracing for this diagnostic trouble code (DTC) or make another attempt.

Do you want to exit fault-tracing?

Yes - FAULT-TRACING FAILED

No - Attempt New Test

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FAULT-TRACING FAILED - FAULT-TRACING FAILED

Attempt New Test - Checking the function of the fuel pump (FP)

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