The complaint
A 2013 Infiniti G37 equipped with the RE7R01A transmission and the EXT13C transfer case has a complaint of trouble codes C1204 “4WD Solenoid Malfunction” and C1105 “Right Rear Wheel Speed Sensor Fault” stored. Due to extensive damage, the transfer case was replaced, which did not eliminate the stored codes. The shop then replaced the TCM, but the codes remained. Wiring was checked and was found to be in good condition.
The cause
The technician was about to perform some pinpoint checks when he noticed the right rear tire appeared smaller than the other three tires mounted on the vehicle. The right rear tire was a 225x55x17 size, while the other three tires were 225x65x17 in. size—refer to figure 1, above. The second pair of digits in the tire size represent the tires aspect ratio which is the width of the sidewall, which affects the tires total circumference.
This means that the 225x55x17 tire has a total circumference of 84.02 inches, while the 225x65x17 tire has a total circumference of 89.58 inches. This is a difference of 5.56 inches of total tire circumference, as seen in figure 2. This is enough of a difference in tire size to cause the trouble codes to set, when in fact there was no problem with the related components.
The correction
We have learned from experience that more than ¼-in. of total tire circumference can cause operational issues with “active” transfer cases and differentials. Therefore, changing the right rear tire to a 225x65x17 size allowed the trouble codes to clear, resulting in proper operation of the vehicle. This is why it is best to use a stagger gauge when trying to determine if a tire size difference is causing a complaint.
Service information
A good website to use to determine the result of tire size differences is the tire size calculator at Tacoma World. It displays complete tire dimensions as well as the difference in speedometer readings for a particular tire size.
Read more articles in our Transmission Tech/Talk series here.
