Signal Too Low
Signal too low
Checking the function of the fuel pump (FP)
- Ignition on (with additional heater start the engine)
Note! On cars where the heater functions as a parking heater there is no +15 voltage supply to the control module. The heater is activated using the timer stop and start buttons instead of VIDA vehicle communication. Individual components and functions cannot be activated when the +15 voltage supply is absent.
- Activate the heater.
Check the function of the heater according to Test running the additional heater / parking heater Initial Inspection and Diagnostic Overview.
Does the heater operate?
Yes - Intermittent fault
No - Checking the connectors
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Checking the connectors
Hint: The fuel pump (FP) is installed in the fuel tank instead of on the heater when the additional heater is also used as a parking heater.
- Ignition off
- Check the fuel pump (FP) and the control module connectors. Check for contact resistance and oxidation according to Checking wiring and terminals. Permanent fault Checking Wiring And Terminals. Permanent Fault. Remedy if necessary.
Check for damage carefully
- Reinstall the components, reconnect the connectors etc.
- Ignition on (with additional heater start the engine)
Note! On cars where the heater functions as a parking heater there is no +15 voltage supply to the control module. The heater is activated using the timer stop and start buttons instead of VIDA vehicle communication. Individual components and functions cannot be activated when the +15 voltage supply is absent.
- Activate the heater.
Check the function of the heater according to Test running the additional heater / parking heater Initial Inspection and Diagnostic Overview.
If the heater now functions, the cause of the fault was loose connections in the connectors.
Other information:
- To access the control module or connect the breakout box,
- To access or replace the fuel pump (FP) see Replacing the fuel pump Fuel Pump, Auxiliary Heater, Replacing.
Does the heater operate?
Yes - FAULT FOUND
No - Checking the overheat protection thermostat
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Checking the overheat protection thermostat
- Ignition off.
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.
Other information:
- To access or replace the overheat protection thermostat, see Overheating protection thermostat, flame sensor and Coolant temperature sensor, replace Replacing Overheat Protection, Thermostat Flame Sensor And Coolant Temperature Sensor.
Was a fault detected?
Yes - Verification
No - Checking components and wiring
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Checking components and wiring
Check the cable between control module terminal #13 and fuel pump (FP) terminal 2. Check for an open-circuit according to Checking wiring and terminals. Permanent fault Checking Wiring And Terminals. Permanent Fault. Check for a short-circuit to ground according to Checking wiring and terminals. Permanent fault Checking Wiring And Terminals. Permanent Fault.
Check the cable between control module terminal #11 and fuel pump (FP) terminal 1. Check for an open-circuit according to Checking wiring and terminals. Permanent fault Checking Wiring And Terminals. Permanent Fault.
Replace the fuel pump (FP) if no fault is found in the wiring.
Note! If there is a fault in the power supply cable, diagnostic trouble code (DTC) HEA-815 Combustion fan, signal and/or HEA-822 Water pump, signal may be stored.
Remedy as necessary.
Other information:
- To access the control module or connect the breakout box,
- To access or replace the fuel pump (FP) see Replacing the fuel pump Fuel Pump, Auxiliary Heater, Replacing
- For other values, see Signal specification Additional heater 912-D/B Signal Specification Additional Heater 912-D/B.
Select Continue.
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 (with additional heater start the engine).
Note! On cars where the heater functions as a parking heater there is no +15 voltage supply to the control module. The heater is activated using the timer stop and start buttons instead of VIDA vehicle communication. Individual components and functions cannot be activated when the +15 voltage supply is absent.
- Activate the heater.
Check the function of the heater according to Test running the additional heater / parking heater Initial Inspection and Diagnostic Overview.
Does the heater operate?
Yes - VERIFIED
No - VERIFICATION FAILEDPAPER
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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 - 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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Intermittent fault
Hint: The fuel pump (FP) is installed in the fuel tank instead of on the heater when the additional heater is also used as a parking heater.
Check the fuel pump (FP) and control module connectors. Check for contact resistance and oxidation according to Checking wiring and terminals. Permanent fault Checking Wiring And Terminals. Permanent Fault.
Check the cable between control module terminal #13 and fuel pump (FP) terminal 2. Check for an intermittent open-circuit according to Checking wiring and terminals. Permanent fault Checking Wiring And Terminals. Permanent Fault. Check for a short-circuit to ground according to Checking wiring and terminals. Permanent fault Checking Wiring And Terminals. Permanent Fault.
Check the cable between control module terminal #11 and water pump terminal 1. Check for an intermittent open-circuit according to Checking wiring and terminals. Permanent fault Checking Wiring And Terminals. Permanent Fault.
Remedy as necessary.
Other information:
- To access the control module or connect the breakout box,
- To access or replace the fuel pump (FP) see Replacing the fuel pump Fuel Pump, Auxiliary Heater, Replacing
- For other values, see Signal specification Additional heater 912-D/B Signal Specification Additional Heater 912-D/B.
Select Continue.
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 the function of the fuel pump (FP)
DONE - DONE
FAULT FOUND - FAULT FOUND
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