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.
• 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 DIAGNOSIS AND TESTING - DRIVER HEATED SEAT SWITCH  or DIAGNOSIS AND TESTING - PASSENGER HEATED SEAT SWITCH  . 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 DIAGNOSIS AND TESTING - DRIVER HEATED SEAT SWITCH  or DIAGNOSIS AND TESTING - PASSENGER HEATED SEAT SWITCH  . 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 DIAGNOSIS AND TESTING - HEATED SEAT ELEMENT  . If not OK, replace the faulty circuit breaker.