Checking Seat Heating Module (SHM)
Checking Seat heating module (SHM)
Checking the seat heating
The system for seat heating consists of three different parts:
- The task of the Seat heating module (SHM) is to check the function and to communicate with the Climate control module (CCM).
- Two heating elements.
- A temperature sensor.
On certain markets, it is not permitted to have seat heating in the vehicle. Check to see if the vehicle has seat heating by clicking the VCT2000 symbol.
Does the vehicle have seat heating?
Yes - Checking symptoms
No - ANOTHER TEST
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Checking communication faults
If the seat heating does not work, this may be because the Seat heating module (SHM) is damaged, that there is no communication with the Seat heating module (SHM) or that the temperature sensor is damaged.
Check communication by clicking on the VCT2000 symbol and reading off the status for seat heating.
Could the status be read out?
Yes - Checking the control module
No - Checking communication
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Checking the control module
Start by replacing the left Seat heating module (SHM) with the right Seat heating module (SHM) and checking that the affected side now works. If both Seat heating modules (SHM) are damaged, replace one with a new one and check the function of each.
Replace damaged control module.
Other information:
- Seat heating module (SHM), replacing Service and Repair
Is the function OK?
Yes - FAULT FOUND
No - Checking heater elements
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Checking heater elements
Continue fault tracing by replacing the temperature sensor and the two heating elements in the damaged seat. Activate the seat heating. Check that the seat heats up.
Also check the function of the Seat heating module (SHM) which was installed from the start. If seat heating works, keep the original control module.
Other information:
- Heater pad backrest and cushion, replacing Service and Repair
- Seat heating module (SHM), replacing Service and Repair
Do you want to exit fault-tracing?
Yes - FAULT FOUND
No - Checking the seat heating
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Checking communication
The fault is probably communication related.
Continue checking the LIN bus to the climate control module (CCM) to fault trace the communication.
Do you want to exit fault-tracing?
Yes - ANOTHER TEST
No - Checking the control module
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Checking symptoms
Check if the vehicle has problems with both seat heating and climate unit or only the seat heating.
Does the vehicle only have problems with seat heating?
Yes - Checking communication faults
No - Fault-tracing information
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Fault-tracing information
This troubleshooting only applies to vehicles that have problems with the climate units and seat heating. Example of symptoms is uneven temperature of air supply for left and right sides of the passenger compartment as well as lost function for seat heating.
Note! Before starting this symptom troubleshooting, check that no relevant diagnostic trouble codes are stored for the vehicle's climate unit.
Climate control module (CCM) and seat heating module communicates via standardized serial communication - LIN (Local Interconnect Network). If Seat Heating Module (SHM) is damaged, this may cause problems with both climate unit and seat heating. Then it is not possible to perform calibration of Climate control module (CCM).
To check if Seat Heating Module (SHM) driver side is damaged, do the following:
1. Disconnect Seat Heating Module (SHM), driver's side.
2. Check if the climate unit works correctly.
If the climate unit works correctly without Seat Heating Module (SHM) driver's side connected, then Seat Heating Module (SHM) driver's side shall be replaced.
3. Do the same check on Seat heating module (SHM), passenger side.
Remedy as necessary.
Other information
- Seat heating module (SHM), replacing Service and Repair
Continue - DONE
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