DTC P1682: Ignition 1 Switch Circuit 2
There are 2 ignition 1 voltage circuits supplied to the engine control module (ECM). The first ignition 1 voltage circuit is provided by the powertrain relay, through a fuse. This ignition 1 voltage circuit supplies power to all the internal ECM circuits associated with the throttle actuator control (TAC) operation. The ignition main relay provides the second ignition 1 voltage circuit to the ECM, through a fuse. This ignition 1 voltage provides power to other internal ECM circuits, except those associated with TAC operation. The ECM continuously monitors the voltage level difference between the two circuits.
You can find a wiring diagram here http://www.bbbind.com/free_tsb.html
Enter your vehicle info. year , make , model engine size . Under system click on Engine ,under subsystem click on fuel controls. Then click on the search button ,then click on the blue link . The first diagram is the one you want . powertrain relay an IGN main relay .
What problem are you having ?
Ignition 1 Voltage (Ignition Main Relay)
P1682, B1370, B1380
Ignition ON, observe the Ignition 1 Signal and EC Ignition Relay Feedback scan tool parameters to determine which is less than B+.
Ignition OFF, remove the relay that corresponds to the scan tool parameter that is less than B+.
Important: 6 ohms or greater in the circuit/underhood fuse block will cause the DTC to set.
Ignition On, connect a 3A fused jumper wire between B+ and the applicable ignition 1 circuit terminal. Verify that the applicable scan tool parameter displays B+.
? If the applicable scan tool parameter is less than the specified value, test the ignition 1 circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
If all circuits test normal, test or replace the applicable relay.