This article’s subject vehicle is a 2006 Jeep Commander, 4×4, with the 5.7 Hemi engine. The concern is every month when the vehicle starts from cold, and is driven about one mile, the dash warning lights illuminating. All are from the braking system, Anti lock disengaged, anti skid problem, 4 wheel drive problem illuminate. Each time the shop examines the fault they end up replacing a brake sensor on one of the rear wheels and that extinguishes the warning lights for about another month. The owner appreciates the free loaner for the two or three days they keep the vehicle but it is an inconvenience.
Let’s get to work! First step is to verify the concern. The technician allowed the vehicle to sit over night as instructed by the owner. The next morning within a mile from start-up the dash warning lights illuminated! It looked like Christmas Lights on a Christmas tree. Back to the shop for a visual inspection of the brake system, Antilock brake system, and stability control system. The technician found no obvious damage to any of the sensors or wiring for these systems.
The scan-tool was connected to the vehicle and retrieved a Diagnostic Trouble Code (DTC) P0116 for the Engine Coolant Temperature Sensor, 1 Circuit Range/Performance. One would think this would have nothing to do with the traction control warning lights illuminating. A check for TSBs to match the code or concern resulted in a Technical Service Bulletin (TSB) for this code causing the lights to illuminate. The TSB instructed the technician to reflash the vehicle to eliminate the customer concern.
The procedure for reprogramming the vehicle was performed following the manufacturers steps to obtain the correct results. The vehicle was driven with no other concerns found during the test drive. The next day the vehicle was driven and the dash did not illuminate with any warning lamps. The vehicle was returned to the owner.
Several days later the owner contacted the technician and reported that the problem had not occurred at all and that the radio was working better? Further questioning of the owner by the technician revealed that he also had a radio problem and did not mention this when he brought the vehicle in for the original concern. The technician reflected on the vehicle and remembered that the radio was turned off during the test drives and diagnostic procedures. Shop policy strictly prohibits tampering with customers radios. The only thing a technician should do is lower the volume if needed.
The case of the “Christmas Tree dash” was resolved by following sound diagnostic practices and this lead to a correct repair. The diagnostic trouble code leads to a TSB that required a reprogramming to resolve the complaint. The customer should always inform a technician of all concerns even if they think they are unrelated. Most reprograms from a manufacturer will repair many problems within a vehicle that may or may not be obvious to the owners.