DTC 15 - P1768

Name of Code:
P-1768(15) - Relay Output Always Off

When Monitored: Continuously.

Set Condition: This code is set when less than 3 volts are present at the Trans Relay Output (switched battery) terminals at the Transmission Control Module (TCM) when the TCM is energizing the relay.

Theory of Operation: The transmission control relay is used to supply power to the solenoid pack when the transmission is in normal operating mode. When the relay is off, no power is supplied to the solenoid pack and the transmission is in "limp-in" mode. The relay output is fed back to the TCM through pins 16 and 17. It is referred to as the Trans Relay Output circuit or "switched battery".
After a controller reset (ignition key turned to the 4~run" position or after cranking engine), the controller energizes the relay. Prior to this the TCM verifies that the contacts are open by checking for no voltage at the switched battery terminals. After the relay is energized, the TCM monitors the terminals to verify that the voltage is greater than 3 volts.

Transmission Effects: The MIL illuminates and the transmission system defaults to Relay Open limp-in mode.

Possible Causes:
- Relay failure (intermittent relay function caused by oxidized or contaminated relay contacts)
- Short to ground or open circuit in the transmission control relay circuit(s)
- TCM connector problem
- TCM