Signal Too Low

Signal too low

Checking fuel pump (FP) function




- Ignition on.
- Activate heater.
Check heater function according to Test driving of Additional heater/Parking heater Initial Inspection and Diagnostic Overview.





Does the heater function?

Yes - Intermittent fault

No - Checking the connectors

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Checking the connectors








- Ignition off.
- Remedy fuel pump (FP) and control module connector for contact resistance and oxidation according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault.
Check any damage etc.
- Reinstall components, reconnect connectors etc.
- Ignition on.
- Activate heater.
Check heater function according to Test driving of Additional heater/Parking heater Initial Inspection and Diagnostic Overview.
If the heater works the cause of the fault has been loose connections in the connectors.

Other information:
- To access the control module/connect breakout box see.
- To access/replace the fuel pump (FP) see Replacing fuel pump Service and Repair.





Does the heater function?

Yes - FAULT FOUND

No - Checking overheat protection thermostat

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Checking overheat protection thermostat
- Ignition off.
Measure between overheat protection thermostat terminals with an ohmmeter. Resistance must be approximately 0 ohms.
If the value does not match this the overheat protection thermostat should be replaced.

Other information:
- To access/replace the overheat protection thermostat see Replacing overheat protection, thermostat flame sensor and coolant temperature sensor Service and Repair.









Was a fault detected?

Yes - Verification

No - Checking component and cables

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Checking component and cables
Check cable between control module #13 and fuel pump (FP) terminal 2 for an open-circuit according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault and a short-circuit to ground according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault.
Check cable between control module #11 and fuel pump (FP) terminal 1 for an open-circuit according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault.
If no faults are found in the cables the fuel pump (FP) should be replaced.

Note! Diagnostic trouble code (DTC) HEA-815 Combustion fan signal and/or diagnostic trouble code (DTC) HEA-822 Water pump signal may also be stored if there is a fault in the power cable.

Remedy as necessary.

Other information:
- To access the control module/connect breakout box see.
- To access/replace the fuel pump (FP) see Replacing fuel pump Service and Repair.
- For other values, see Signal specification Additional heater 912-D/B Signal Specification Additional Heater 912-D/B.













Continue - Verification

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Verification




Verification

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








- Ignition off.
- Reinstall connectors, components etc.
- Ignition on.
- Activate heater.
Check heater function according to Test driving of Additional heater/Parking heater Initial Inspection and Diagnostic Overview.





Does the heater function?

Yes - VERIFIED

No - VERIFICATION FAILED

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VERIFICATION FAILED - Fault-tracing information

VERIFIED - FAULT FOUND

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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 - Exit fault-tracing

No - Attempt New Test

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Attempt New Test - Checking fuel pump (FP) function

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Intermittent fault
Check fuel pump (FP) and control module connector for contact resistance and oxidation according to Checking wiring and terminals. Intermittent faults Checking Wiring and Terminals. Intermittent Faults.
Check cable between control module #13 and fuel pump (FP) terminal 2 for an intermittent open-circuit according to Checking wiring and terminals. Intermittent faults Checking Wiring and Terminals. Intermittent Faults and a short-circuit to ground according to Checking wiring and terminals. Intermittent faults Checking Wiring and Terminals. Intermittent Faults.
Check cable between control module #11 and water pump terminal 1 for an intermittent open-circuit according to Checking wiring and terminals. Intermittent faults Checking Wiring and Terminals. Intermittent Faults.
Remedy as necessary.

Other information:
- To access the control module/connect breakout box see.
- To access/replace the fuel pump (FP) see Replacing fuel pump Service and Repair.
- For other values, see Signal specification Additional heater 912-D/B Signal Specification Additional Heater 912-D/B.













Continue - Fault-tracing information
DONE

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Fault-tracing information




Information

Fault-tracing information
If the fault is intermittent, do not verify fault-tracing if the fault does not recur.
It is possible to view the information again, or leave fault-tracing for this diagnostic trouble code (DTC).

Do you want to view the information again?

Yes - Attempt New Test

No - FAULT FOUND

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Attempt New Test - Checking fuel pump (FP) function

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