SES MIL With DTC P1682 - keywords fuel level pump transfer sensor sender

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Some owners may comment of a SES MIL with a DTC P1682. If normal diagnostics does not lead to a correction, this concern could be caused by the rear fuel tank sender assembly being mispositioned. If the rear fuel tank sender assembly is mispositioned, it could give an improper fuel level reading to the ECM. The sender reading may indicate that there is fuel in the rear tank when actually the tank will be empty. With the ECM sensing fuel in the rear tank, it could command the transfer pump on, trying to transfer fuel from the rear tank to the front but the rear tank will be empty. With the fuel tank empty the transfer pump will be running "Dry" with no load. If the ignition key is shut off while the transfer pump is commanded on, as the transfer pump spins down it could back feed voltage on circuit 439 to the UBEC. Circuit 439 is one of the circuits that the ECM monitors when performing the diagnostic for DTC P1682.

Note: During normal operation if the transfer pump was commanded on to transfer fuel and the ignition key is shut off, the transfer pump spin down time is reduced due to the load of pumping fuel and the concern does not occur.

To determine if this is the concern, disconnect the transfer pump relay and see if the concern goes away. If the concern is gone, then measure the resistance of the rear tank sender. The resistance reading should be 250 ohms (+/-3 ohms) when the tank is empty. If the resistance is less than the spec verify the tank is empty by removing the sender assembly. If the fuel tank is empty check the resistance of the fuel level sensor when manually moving the float arm up and down. When the sender is all the way up, the resistance should be 40 ohms (+/-3 ohms) and when down it should be 250 ohms (+/-3 ohms). If the sender is operating properly, reinstall the sender assembly making sure it is inserted straight down into the tank, not on an angle. With the sender properly installed and the fuel tank empty, re-measure the resistance of the fuel level sensor and verify it is 250 ohms (+/- 3 ohms).

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.