Circuit/System Testing

The 5 volt reference circuit and the switch signal will have to be checked for shorts to ground, opens, high resistance, and shorts to voltage by following the below listed steps.

1. Reference the mode switch supply voltage with a scan tool.
   • The scan tool should indicate 4.8-5.2 volts. If the scan tool indicates the voltage is within this specification then with a jumper wire short the switch signal circuit pin C1 pin 1 on the switch to the 5 volt reference circuit C1 pin 9 on the switch. If the rear differential lock switch return voltage on the scan tool measures 4.8-5.2 volts then replace the switch.
2. If the rear differential lock switch return does not read 4.8-5.2 volts check the rear differential lock switch signal circuit and the 5 volt reference circuits for a short to ground, short to voltage, open, or high resistance.
   • If no shorts or high resistance are found on the switch signal or 5 volt reference circuits then replace the transfer case shift control module.