Heated Seat System

In order to obtain conclusive testing of the heated seat system, the Programmable Communications Interface (PACE) data bus circuit must be checked.

The most reliable, efficient, and accurate means to diagnose the heated seat system requires the use of a DRB III(R) scan tool and the Service and Body Diagnostic Procedures Manuals. The DRB III(R) scan tool can provide vital information to the technician trying to find a problem with the heated seat system. Diagnostic logic is built into the memory heated seat/mirror module to help the person trying to locate the problem by the most efficient means possible. Anytime a problem is suspected, a DRB III(R) scan tool must be obtained and used to retrieve any stored fault codes in the memory heated seat/mirror module. If diagnostic fault codes are present in the module, record them on a piece of paper immediately before proceeding any further. Then, use these fault codes to identify the problem by verifying the fault code. Example, If the module records "DRIVER SEAT HEAT OUTPUT OPEN" fault, locate the diagnostic procedure for this code in the appropriate Body Diagnostic Procedures Manual and follow the flow chart until the specific problem is located and resolved. Once the problem is thought to be corrected, erase the stored fault code using the DRB III(R) scan tool and verify correct system operation. If the heated seat system is functioning correctly, verify that there are no other stored codes in the module and return the vehicle to service.

If the fault code could not be verified, such as not finding anything wrong when following the diagnostic flow chart in the Body Diagnostic Procedures Manual. This is a good indication that a INTERMITTENT problem may be present. You must then attempt to find the intermittent problem, such as moving the heating element within the seat while testing continuity or wiggling the wire harness's/electrical connectors under the seat while testing continuity. Always, eliminate all other potential problems before attempting to replace the memory heated seat/ mirror module.

For complete circuit wiring diagrams, refer to Wiring.

WARNING: REFER TO THE RESTRAINTS SECTION BEFORE ATTEMPTING ANY SEAT, STEERING WHEEL, STEERING COLUMN, OR INSTRUMENT PANEL COMPONENT DIAGNOSIS OR SERVICE. FAILURE TO TAKE THE PROPER PRECAUTIONS COULD RESULT IN ACCIDENTAL AIRBAG DEPLOYMENT AND POSSIBLE PERSONAL INJURY.

PRELIMINARY TEST
Before testing the individual components in the heated seat system, check the following:
- Using the DRB III(R) scan tool, check the memory heated seat/mirror module (MHSMM) for any stored fault codes. Record these codes on paper for reference and resolve using the appropriate Body Diagnostic Procedures Manual.
- Check the vehicles battery open-circuit voltage and charging system performance. If the vehicles electrical system is defective or weak it may not be suppling sufficient energy to operate the heated seat system.
- If the heated seat switch backlighting does not light with the ignition switch in the On position, check the fused ignition switch fuse in the junction block and the G300 ground splice. If OK, refer to Heated Seat Switch Diagnosis and Testing. If not OK, repair the shorted circuit or component as required and replace the faulty fuse or repair the open ground circuit as required.
- If the heated seat switch HI/LO LED indicators do not light with the ignition switch in the On position and the heated seat switch in the Low or High position, check the fused ignition switch fuse in the junction block. If OK, refer to Heated Seat Switch Diagnosis and Testing. If not OK, repair the shorted circuit or component as required and replace the faulty fuse.
- If the heated seat switch HI/LO LED indicators light, but the heating elements do not heat, check circuit breaker #2 in the junction block. If OK, refer to Heated Seat Element Diagnosis and Testing. If not OK, replace the faulty circuit breaker.