Faulty Signal
Faulty signal
Signal too low
Checking waterflow
Check if the lines to and from the heater are blocked or if the heater is damaged so that through flow is restricted in some way.
Remedy as necessary.
Was a fault detected?
Yes - Verification
No - Checking coolant temperature sensor
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Checking coolant temperature sensor
- Start engine.
- Read off coolant temperature in the heater.
Check the engine coolant temperature (ECT) reading is correct. Compare with the actual coolant temperature of the engine.
Is the temperature reading OK?
Yes - Checking component and cables
No - Checking component and cables
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Checking component and cables
Check engine coolant temperature sensor resistance. For resistance values refer to Component resistance values Component Resistance Values.
Remedy as necessary.
Other information:
- To access/replace Coolant temperature sensor see Overheating protection thermostat, flame sensor and Coolant temperature sensor, replace Replacing Overheat Protection, Thermostat Flame Sensor And Coolant Temperature Sensor.
- 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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Checking component and cables
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 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 cable between control module #13 and fuel pump (FP) terminal 1 for an intermittent open-circuit according to Checking wiring and terminals. Intermittent faults Checking Wiring And Terminals. Intermittent Faults.
Check cable between control module #11 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.
Note! Diagnostic trouble code (DTC) HEA-815 Combustion fan signal and/or diagnostic trouble code (DTC) HEA-822 water pump signal is stored if there is a fault in the power cable.
Remedy as necessary.
Other information:
- To access the control module/connect breakout box
- To access/replace the fuel pump (FP) see Replacing the fuel pump Fuel Pump, Auxiliary Heater, Replacing.
- To access/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.
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 waterflow
FAULT FOUND - FAULT FOUND
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FAULT FOUND - FAULT FOUND
No Fault Found - No Fault Found
FAULT-TRACING FAILED - FAULT-TRACING FAILED
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