DHS/DTS & DeVille Rear Seat Diagnostic Procedure
1. Remove the rear seat cushion assembly (1) from the vehicle. Refer to Seat Cushion Replacement Rear in the Seats sub-section of the Service Manual.
Important:
If the resistance is measured with the seat still warm, the resistance may vary outside of the specified range since the thermistor resistance varies with temperature.
2. At the rear seat cushion blue, 8-way connector C320 (2), measure the thermistor resistance.
^ For the LH rear seat cushion, measure between cavities C and D. Does the resistance measure between 280 ohms and 300 K ohms?
^ For the RH rear seat cushion, measure between cavities G and H. Does the resistance measure between 280 ohms and 300 K ohms?
^ If yes, go to Step 3.
^ If no, install a rear seat cushion (center) heat element. Refer to the Service Heat Element Installation Procedure in this bulletin.
3. At the rear seat cushion blue, 8-way connector C320 (2), measure the element resistance.
^ For the LH rear seat cushion, measure between cavities A and B. Does the resistance measure less than 10 ohms?
^ For the RH rear seat cushion, measure between cavities E and F. Does the resistance measure less than 10 ohms?
^ If yes, go to Step 8.
^ If no, for DeVille models ONLY, install a rear seat cushion heat element. Refer to the Service Heat Element Installation Procedure in this bulletin.
^ If no, for DHS & DTS models ONLY, go to Step 4 in order to determine which of the three rear seat cushion heat elements has a resistance value NOT within the specified range.
4. For DHS & DTS models ONLY: Remove the trim cover from the rear seat cushion. Refer to Seat Cushion Cover Replacement-Rear in the Seats sub-section of the Service Manual.
5. For DHS & DTS models ONLY: At the LH/RH rear seat cushion, disconnect the green 2-way connectors between the seat cushion center heat element and the seat cushion thigh heat elements.
6. For DHS & DTS models ONLY: Measure the LH seat cushion thigh heat element resistance between cavities A and B at the green 2-way connector. Does the resistance measure less than 30 ohms?
^ If yes, go to Step 7.
^ If no, install a rear seat cushion LH thigh heat element. Refer to the Service Heat Element Installation Procedure in this bulletin.
7. For DHS & DTS models ONLY: Measure the RH seat cushion thigh heat element resistance between cavities A and B at the green 2-way connector.
Does the resistance measure less than 30 ohms?
^ If yes, install a rear seat cushion (center) heat element. Refer to the Service Heat Element Installation Procedure in this bulletin.
^ If no, install a rear seat cushion RH thigh heat element. Refer to the Service Heat Element Installation Procedure in this bulletin.
8. Remove the rear seat back assembly from the vehicle. Refer to Seat Back Replacement-Rear in the Seats sub-section of the Service Manual.
9. At the rear seat back LH (1) or RH (2) heated seat module, disconnect the blue, 8-way connector C2.
Important:
If the resistance is measured with the seat still warm, the resistance may vary outside of the specified range since the thermistor resistance varies with temperature.
10. Measure the rear seat back thermistor resistance between cavities E and F. Does the resistance measure between 280 ohms and 300 K ohms?
^ If yes, go to Step 11.
^ If no, install a rear seat back heat element. Refer to the Service Heat Element Installation Procedure in this bulletin.
11. Measure the rear seat back element resistance between cavities G and H. Does the resistance measure less than 10 ohms?
^ If yes, the resistance values of the rear seat heat elements are within the specified range. To find the cause of the inoperative/cold rear heated seat, perform the standard diagnostic procedures in the Service Manual.
^ If no, install a rear seat back heat element. Refer to the Service Heat Element Installation Procedure in this bulletin.